CA1335710C - Remote sensing tonometric catheter apparatus and method - Google Patents
Remote sensing tonometric catheter apparatus and methodInfo
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- CA1335710C CA1335710C CA000609067A CA609067A CA1335710C CA 1335710 C CA1335710 C CA 1335710C CA 000609067 A CA000609067 A CA 000609067A CA 609067 A CA609067 A CA 609067A CA 1335710 C CA1335710 C CA 1335710C
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Abstract
A remote sensing tonometric catheter apparatus (20) and method for sampling of a fluid or gas property of interest in a hollow internal organ. The tonometric catheter (20) assists in early detection of the problems of stress ulceration and/or intestinal ischemia. The tonometric catheter (20) has one or more sampling chambers (40) for introduction into a hollow internal organ or an area adjacent thereto. The tonometric catheter (20) has an electric sensor (42) for developing a signal indicative of the condition of the organ. Electric sensor (42) is in communication with the sampling chamber (40). The sensor (42) has a conductor (56) coupled therewith for conveying the signal to a location outside the organ such that the condition of the organ may be remotely determined. Preferably, the wall (36) of the sampling chamber (40) is freely permeable to the gas or fluid to be measured by the sensor (42), but is poorly permeable to other gases or fluids which may interfere with the sensor (42). The method is accomplished by introducing the catheter into the organ such that the sampling chamber is disposed at a portion of the wall of the organ. The sampling chamber is left in position at the wall of the organ for a time sufficient to allow the fluid or gas of interest to diffuse into the sampling chamber. The concentration of the fluid or gas of interest is analyzed. The pH of the wall of the organ may be calculated based on the concentration of the fluid or gas property of interest.
Description
REMOTE 8EN8ING TONOMETRIC CA-nh~ n APPAR~TUB A~JD METHOD
Baclcqround, and ~3umm~ry of the Invention This invention relates to medical diagnostic equipment and methods and is particularly concerned with hollow viscus tonometry and remote electronic and optical sensing.
The prior art (see U.S. Patent No. 4,643,192) has recognized that intestinal ischemia, and to a lesser degree, stress ulceration, are two problems that plague physicians involved in the management of patients in intensive care units.
Intestinal ischemia, in particular, has an insidious onset and may not be detected until days after the intestine has become completely and irreversibly compromised. A delay in the diagnosis of intestinal ischemia may have devastating consequences for a patient. The availability of means for early diagnosis and management of patients with these problems would have immediate applicability in all intensive care units, especially where the procedure can be conveniently conducted with reasonable safety and reliability.
It has been established that a fall in the intramucosal pH may precede the development of intestinal ischemia and stress ulceration. As I reported in my prior U.S. Patent No. 4,643,192, entitled "Hollow Viscus Tonometry" a fall in intramucosal pH also occurs within minutes of inducing intestinal ischemia in dogs. The fall in pH
in intestinal mucosa, and hence the likelihood of ischemia or stress ulceration, can be reliably calculated from a PC02 (partial pressure of C02), or other indicia of pH, in luminal fluid and the bicarbonate concentration in arterial blood. The -t ~, '"7, 1 3357 ~ O
method of calculating the pH in intestinal mucosal tissue, pursuant to principles of my prior patent, has been validated by directed measurements under a variety of conditions simulating clinical problems. A correlation coefficient in the order of 0.92 to 0.95 has been obtained in each of 16 dogs. The validity of the procedure is inherently extensible to humans, and indeed may also be useful in assessing the vitality of other hollow organs and tissue. See R.G. Fiddian-Green et al. "Splanchnic Ischemia and Multiple Organ Failure".
To measure the PC2 in the lumen of the gut it has heretofore been necessary to obtain and remove a sample of fluid that has been in contact with the wall of the gut for a certain time period, usually at least half an hour. It has now been observed that it is somewhat difficult to manually aspirate the sampling fluid or medium from a tonometric catheter located in the gut or other internal focus with any consistency. It is much easier to obtain ~uch samples from the stomach, but samples obtained from the stomach frequently contain foreign material that can damage a gas analy~er.
, As taught in my prior patent, the desired sample or samples can be obtained from the gut using a catheter tube (called a tonometric catheter) having a walled sampling chamber on the tube with the sampling chamber being in sample-specific communication with the hollow interior of the tube. The wall of the sampling chamber comprises a material which is substantially impermeable to liquid yet is highly permeable to gas. One suitable material is polydimethylsiloxane elastomer.
In use the catheter is introduced into a patient to place the sampling chamber at a desired site within the gut. An - ~ 3357 1 0 aspirating liquid or medium is employed to fill the interior of the sampling chamber. The sampling chamber is left in place at the desired sampling site long enough to allow the gases present to diffuse through the wall of the ~ampling chamber into the aspirating liquid. The time should be long enough for the gases to equilibrate. The liquid impermeable nature of the sample chamber wall material prevents both the aspirating liquid from leaking out of the chamber and also the intrusion of any liquids into the aspirating liquid. After the appropriate or desired amount of placement time has elapsed the aspirating liquid is aspirated along with the gases which have diffused into it. The sample thus obtained is analyzed for gas content, in particular for pC02. In this way the PC02 within the lumen of the gut can be reliably measured with the fluid being free from lumenal debris.
In carrying out the diagnostic method taught in my prior patent the PC02 measurement is utilized in conjunction with a measurement of the bicarbonate ion concentration (HC03 ) in an arterial blood sample of the patient for determining the pH of the tract wall.
Depending upon the particular condition of a given patient, the catheter may be left in place and samples may ~e taken at periodic intervals so that pH values may be periodically calculated. The procedure has a high reliability in accurately determining the adequacy of organ tissue oxygenation, and diagnosing intestinal ischemia in its incipient ~tages. Such determination or detection can be useful in treating the patient so that the potentially devastating consequences resulting from less timely detection may often be avoided.
While the sampling techniques taught in my prior patent have provided highly accurate and reliable results, it has now been observed that there are instances (in the care of the critically ill in intensive care units, for example) in which remote sensing of the organ or organ-wall condition and automatic calculation of the organ or organ-wall pH would be advantageous and easier to effectuate. This method would thus partially or totally eliminate the need for the somewhat cumbersome aspiration of the sampling fluid or medium which fills the sampling chamber;
it may also eliminate the need for the sampling chamber to be in ~ampling-medium communication with any other part of the device.
There is also a need to extend the benefits of tonometric ~ampling and ~ensing to other internal hollow viscous organs. To this end, there is a need for new and different tonometric devices specifically adapted to allow my sensing and ~ampling techniques to be performed with ease in a clinical environment, and in combination with other procedures.
The importance and ~ignificance of determining the pH
of the wall of a given hollow viscous organ has been recently dràmatically magnified as a result of the recent recognition that the pH of the wall of a given organ can be employed to accurately evaluate the vitality and/or stability of that organ as well as others: this is in contrast to merely determining whether such an organ is experiencing an ischemic event. Further, certain organs can be selected for monitoring, either alone or in combination, and evaluation of this organ or these organs can aid in predicting the overall condition of the patient, or the onset of a multitude of pathologies, including predicting or identifying such events as multiple organ failure. Such a methodology can be employed to greatly enhance and 6upplement the monitoring of the critically ill, for example.
In one aspect, the present invention provides a new apparatus and method for remotely 6ensing organ condition and conveying an electromagnetic signal, e.g. an electrical current or optical ~ignal, to an electronic or optical apparatus located outside the organ under investigation. In one embodiment, a chemically sensitive electronic transducer (or plurality of transducers), 6uch as a field effect transistor, is attached to a tonometric catheter for introduction into the organ along with the tonometric catheter. The first electronic sensor, preferably non-temperature, generates and conveys an electromagnetic signal indicative of some desired aspect of organ condition, e.g., indicative of the pC02, pH and/or P02 level of the organ or organ-wall. For example, in one preferred embodiment, mean ambient pC02, pH and/or P2 f lumenal fluid or the like is measured or monitored via wire or other suitable electromagnetic energy conveying means to an electronic circuit which interprets the electromagnetic signal and produces a report of the organ condition. ! The electronic circuit may include an input for receiving a separately determined signal indicative of the blood pH of the patient. Using this pC02, pH and/or P02 measurement along with blood (preferably arterial) pH data, the electronic circuit determines the pH of the organ wall under test and thereby provides information for determining the organ's current condition or perhaps predicting the organ's future condition.
The electronic circuit may be suitably constructed from analog components, digital components or both.
In another embodiment, a pH, PC02 or P02 sensitive colorimetric substance is injected into an area adjacent to the organ, e.g., into the sampling chamber of the tonometric catheter, and an optical sensor is employed to detect color change in order to determine the pH of the wall of that organ.
The optical sensor can either be disposed in or on the tonometric catheter for introduction into the area adjacent the organ or it may be disposed outside the organ with fiber optic cable optically coupling the sensor to the tonometric catheter site at which the pH sensitive substance has been injected.
In another aspect the present invention provides a variety of new and different tonometric catheter devices for sensing and/or sampling a fluid or gas property (such as pH, P02, pC02, and the like) which is indicative of the condition of an internal organ, in conjunction or combination with a walled catheter tube adapted for delivery or draining fluids, such as nasogastric tubes, urinary catheters, ureteric catheters, intestinal feeding tubes, wound or abdominal drains (suction or regular) and biliary tubes, catheters and stents, with or without remote sensing means for pH, PC02 and/or Po2-In still another aspect or embodiment, the deviceemploys two separate walled catheter tubes, one tonometric catheter tube for the measurement of a fluid or gas property, that is in communication with the sampling chamber; and a second walled catheter tube adapted for delivering or draining fluids.
In yet another aspect or embodiment, the device employs a walled sampling chamber in communication with a sensing means, and a second walled catheter tube adapted for delivering or draining fluids.
1 33 ~7 1 ~
Optionally, when a non-temperature sensing-means is employed, a second sensing-means may be employed as well.
For a more complete understanding of the invention, its objects and advantages, reference may be had to the following specification and to the accompanying drawings. Also, see applicant's co-pending Canadian applications filed of even date herewith entitled "Hollow Viscus and Solid Organ Tonometry" and "Tonometric Catheter Apparatus", bearing respective serial numbers 609,066 and 609,065.
~rief Description of the Drawinqs Figure 1 is a plan view of a first embodiment of the tonometric catheter;
Figure 2A is a partial cross-sectional view of the tonometric catheter illustrating a first means for attachment of an electronic field effect transistor sensor;
Figure 2B is a partial cross-sectional view of the tonometric catheter illustrating a second means of attachment of the field effect transistor sensor;
Figure 3 illustrates the method of use of the tonometric catheter in measurement of the pH of the colon and also of the stomach, the specific embodiment illustrated for colonic measurement being that of Figure 5 and the specific tonometric catheter for gastric measurement being that of Figure 4;
Figure 4 is another embodiment of the tonometric catheter with nasogastric tube;
Figure 4A is a cross-sectional view of the tonometric catheter of Figure 4 taken substantially along the line 4A-4A of Figure 4;
Figure 4B is a cross-sectional view of the tonometric catheter of Figure 4 taken substantially along the line 4B-4B of Figure 4;
Figure 5 is yet another embodiment of the tonometric catheter having multiple sensing/6ampling portions;
Figure 5A is a cross-sectional view of the tonometric catheter of Figure 5, taken substantially along the line 5A-5A of Figure 5;
Figure 6 is a detailed view illustrating the tonometric catheter of Figure 4 in use within the stomach;
Figure 7 is a detailed vieW illustrating the tonometric catheter of Figure 5 in use within the colon;
Figure 8 is a similar view illustrating the tonometric catheter of Figure 1 in use within the colon;
Figure 9 is an electrical schematic diagram illustrating one embodiment of electronic circuit in accordance with the invention;
Figure 10 is an electrical schematic diagram illustrating another embodiment of the optical measurement of pH
in accordance with the invention;
Figure 11 is another embodiment of a tonometric catheter with a urinary catheter;
Figure llA is a cross-sectional view of the tonometric catheter/urinary catheter of Figure 11, taken substantially along the line llA-llA of Figure 11.
t 1 3357 ~ ~
De~cript~on of the Preferred Embodiment~
Figure 1 illustrates a first embodiment of tonometric catheter 20. The tonometric catheter comprises a length of suitable tubing 22, one end 32 of which is closed, and the opposite end of which has a connector such as a luer-lock 24.
Luer-lock 24 is adapted to receive a complementary fitting 26, which in turn couples through a ~econd length of tubing 28 to a three-way stopcock 30. Three-way ~topcock 30 may be used to selectively connect tubing 28 to various sources of irrigation or aspiration.
Adjacent the closed end 32, tubing 22 is perforated as at 34. A balloon-like tonometric catheter membrane 36 is fitted over the closed end ~o that the perforations 34 are enclosed, as illustrated. The tonometric catheter membrane 36 has an internal sleeve diameter at 38 which forms a tight fit with tubing 22.
The preferred form of tonometric catheter membrane is polydimethylsiloxane elastomer. The membrane may be sealed to the tubing 22 with appropriate adhesive so that the tonometric catheter membrane is ~ealed in a closed relationship to the outer wall of tubing 22, thereby forming a ~ampling chamber 40 adjacent closed end 32. The tonometric catheter membrane has a certain elasticity to allow the membrane to expand when filled with an aspirating liquid in order to contact the wall of the organ under examination, as will be explained below.
The membrane 36 is preferably constructed such that at least a portion of it is selectively permeable to the gas or fluid property of interest. In a preferred embodiment, it is ~electively permeable to hydrogen, oxygen, or H+, ~o that pH, PC02 and/or P02 can be measured. It i~ also preferably impermeable to other materials that would interfere with the desired measurements, such as other gases, proteins, and the like. In a highly preferred embodiment, an ion-selective membrane is employed.
Bonded to either the inner wall or the outer wall of tubing 22 are one or more sensors 42 for detecting a property indicative of pH and/or temperature. Two such sensors are illustrated in Figure 1, bonded to the outside wall of tubing 22 with ~uitable adhesive. Figures 2A and 2B illustrate two alternate means of ~ensor attachment, Figure 2A illustrating the ~ensor attached to the inner wall of tubing 22 and Figure 2B
illustrating the sensor attached to the outer wall of tubing 22.
In a preferred embodiment, at least a portion of the tubing, but not all of it, i~ made of a C02 impermeable material, such as polyester elastomers derived from the reaction of dimethylterephtalate 1,4-butanediol and o-hydro- Q -hydroxypoly (oxytetramethylene). In a highly preferred embodiment, this is a material such as Hytril, sold by DuPont.
For purposes of censing temperature, thermistor devices are presently preferred. For sensing properties indicative of pH
chemically responsive field effect transistors or "Chemfets" may be employed. In this regard, Chemfet ~ensors 44 have been illustrated in Figures 2A and 2B. Chemfet sensor 44 comprises a field effect ~emiconductor device 46, which is encapsulated in a ~olution impervious material 48, such as a polymerized epoxy resin. The encapsulation material 48 in turn may be encapsulated in a housing 50 (Figure 2A). Semiconductor device 46 is electrically coupled by bonding wires 52 to a terminal 54.
Suitable electrical conductors such as conductor 56 are attached * Trade-mark -- 10 ~
to terminal 54 for electrically communicating between the Chemfet device 44 and the electronic circuitry described below in connection with Figure 9. Conductor 56 is preferably routed through tubing 22 and exits through a sealed aperture at or near the luer-lock end of tubing 22, as at 58. A more detailed description of a cuitable electronic sensor may be found in U.S.
Patent No. 4,020,830 to Johnson, entitled "Selective Chemical Sensitive FET Transducers " In order to allow a solution to contact the chemically sensitive surface of semiconductor device 46, tubing 22 may be provided with an aperture 60 when implementing the embodiment of Figure 2A. Such an aperture is not needed in the embodiment of Figure 2B, Rince the semiconductor device 46 is exposed to sampling chamber 40 by virtue of the external mounting configuration.
The sampling chamber 40 can be filled with an aspiration or sampling medium that is used to absorb or otherwise provide a means for incorporating and delivering or measuring the the fluids or gases of interest. Such a medium is selected depending upon many factors, including the properties of the fluids or gases of interest, the type of censor 42 employed, and the type of calibration that is necessary. Such mediums include bicarbonate solutions and caline solution. It might be noted that gases often behave as fluids and are therefore frequently considered to be fluids.
As noted above, when the ~ensor employed does not require frequent reca'libration, the need for the sampling chamber 40 to be in communication with the proximate end of the tonometric catheter (that remains outside the patient) may be ! i eliminated ~ince no aspiration is needed. However, in many instances ~uch communication may still be desirable as aspiration may be required to calibrate the sensor or ~ensors, to replace the aspirating or ~ampling medium with a fresh medium, and to incorporate the gas or gases of interest.
Another embodiment of the tonometric catheter is illustrated in Figures 4, 4A and 4B. As illustrated, the tonometric catheter is appropriately configured to al60 serve as a nasogastric sump, either with or without gastric suction. With reference to Figure 4, the tonometric catheter 20a comprises a multipassage tubing 62 which defines three individual noncommunicating (between each other) passageways or lumens, an air lumen 64, an optional 6uction lumen 66 and a tonometric catheter lumen 68. A tonometric catheter membrane, similar to that previously described, ifi attached at an intermediate location on tubing 62, allowing a portion of the tubing to extend beyond the end of membrane 36 to define the nasogastric 6ump 70.
Tubing 62 is provided with a plurality of perforations 72 which communicate between tonometric catheter lumen 68 and the sampling chamber 40 defined by membrane 36. If desired, one or more ~ensor~ 42 can be included in accordance with the above teachings, in which case a suitable conductor 56 may be routed through tonometric catheter lumen 68 to exit at sealed aperture 58.
The nasogastric sump portion 70 is ~uitably provided with a plurality of openings 74 through which the stomach may be aspirated.
At the opposite end of tubing 62 the tubing ~plits to form three separate connections. Air lumen 64 communicates with f ~ ~
1 33~7~ 0 air lumen passageway 76, suction lumen connects with suction lumen passageway 78 and tonometric catheter lumen 68 communicates with tonometric catheter lumen passageway 80. The tonometric catheter lumen passageway is fitted with three-way stopcock 30, 6imilar in function and purpose to the three-way stopcock 30 described in connection with Figure 1. If desired, a quick connect fitting 82 may be used to couple the suction lumen passageway 78 with an aspiration source. As illustrated, the quick connect fitting preferably has angularly cut ends and a slightly enlarged midsection, making it easy to insert into the end of passageway 78 and also into the aspiration hose coupling (not shown). The enlarged midsection helps form a seal with the adjoining passageways. Preferably the quick connect fitting is fabricated of disposable plastic.
Yet another embodiment of the tonometric catheter is illustrated in Figures 5 and 5A. This embodiment is a multiple tonometric catheter embodiment employing a tubing 84 having a plurality of passageways or lumen as shown in the cross-sectional vlew of Figure 5A. Specifically, tubing 84 includes an air lumen 86a which communicates with the endmost tonometric catheter 36a and three additional tonometric catheter lumens 86b, 86c and 86d, which communicate respectively with tonometric catheters 36b, 36c and 36d. As with the other embodiments, each tonometric catheter may be provided with one or more 6ensors such as sensor6 42. A radiopaque tungsten plug 88 i6 positioned within each of the three tonometric catheter lumen 86b, 86c and 86d adjacent the distal end of each tonometric catheter, serving to block the remainder of the tonometric catheter lumen passageway and thereby ensuring that fluid pressure introduced into each tonometric catheter lumen will cause the associated tonometric catheter to balloon outwardly as required during use.
Similarly, a radiopaque tungsten rod 90 is fitted as a plug in the end of air lumen 86a, ~erving to terminate the end of the air lumen passageway. Being radiopaque, the tungsten plugs and tungsten rod aid in properly positioning the tonometric catheters by being visible under fluoroscope or x-ray. In addition, if desired, tubing 84 can be provided with a radiopaque stripe along all or part of its length.
At the proximal end of tubing 84 the lumen 86a-86d diverge to define four separate tubes 92a-92d. Each tube is fitted with a three-way stopcock similar to those described above. Each 6ampling connector may optionally be coded numerically by color, etc. While four approximately equally spaced tonometric catheters have been illustrated in Figure 5, it will be understood that the invention can be modified to include a greater or fewer number of tonometric catheters at different spacing as required for a particular application. It will also be understood that 60me or all of the tonometric catheters can include one or more sensors coupled to conductors 56, each preferably routed through the corresponding lumen passageway.
Referring now to Figure 9, a ~uitable electronic monitoring circuit will now be described. In Figure 9 CHEMFET
semiconductor device 46 has been shown schematically by the equivalent circuit model enclosed in dotted lines. The device 46 thus comprises drain electrode 150, source electrode 152 and reference electrode 15i. The chemically selective ~ystem, such as a membrane system is depicted diagrammatically at 156. The substrate is grounded as at 158.
Source electrode 154 is coupled to an input lead of operational amplifier 160 which includès feedback network diagrammatically depicted at 162. Operational amplifier 160 senses the drain source current flowing through device 46 and converts this signal into a voltage signal which is output on lead 164. The drain source current changes in accordance with changes in the chemical ~ystem under test. More specifically, as the PCO2 level changeæ in the fluid exposed to device 46, the drain source current changes accordingly. Hence the output voltage 6ignal on lead 164 is likewise an indication of the PCO2 level of the organ under test. This voltage signal on lead 164 is coupled to an input of comparator 166 which also receives a reference voltage Vref, which may be supplied using a voltage divider network (not shown) or which may alternatively be provided by a digitally controlled voltage source 168. The output of comparator 166 is fed to reference electrode 154 to provide a stable reference bias voltage. If a digitally controlled voltage source is used, this reference voltage can be adjusted and calibrated by a computer circuit yet to be discussed. The voltage signal on lead 164 is also fed to an analog to digital convertor 170, which is in turn coupled to a microprocessor-based microcomputer 172.
In order to automatically determine the pH of the wall of the hollow viscous organ under test, a separate gas analyzer sensor 174 is used to determine the bicarbonate concentration in the arterial blood of the patient. The output of ~ensor 174 is coupled through analog to digital convertor 176 to microcomputer 172. Microcomputer 172 is preprogrammed to calculate the pH of the organ wall using the values provided by 1 3357 ~ O
analog to digital convertors 170 and 176. Conversion of PCO2 measurements can be converted into pH measurements automatically by microcomputer 172 using various equations and references well-known in the art.
Although many different types of output devices may be employed, strip chart recorder 178 and CRT monitor 180 have been illustrated. Strip chart recorder 178 and monitor 180 are coupled as output devices to microcomputer 172. Strip chart recorder 178 offers the advantage of developing an easily readable, permanent record of the fluctuations in organ wall pH.
Monitor 180 offers the advantage of providing digital readout of the pH value as well as displaying the upper and lower excursions of pH fluctuation. If desired, microcomputer 172 can be preprogrammed using keyboard 182 to compare the instantaneous pH
value with doctor-selected upper and lower alarm limits. If the measured instantaneous pH fluctuates outside those limits, microcomputer 172 can sound an alarm to alert hospital staff.
While a single 6emiconductor device 46 has been illustrated in conjunction with the electronic circuit of Figure 9, the circuit may be readily adapted for use with a plurality of 6emiconductor devices in order to measure the pH at different locations substantially simultaneously. In such an embodiment, the data coming from each sensor can be fed to a separate I/O port of microcomputer 172. In the alternative, a single I/O port can be used with the individual input signals being time multiplexed.
As an alternative to electronic pH sensors, the invention may also be practiced using optical sensor technology.
Referring to Figure 10, the presently preferred optical sensor embodiment uses a first fiber optic cable 94 which i8 optically coupled through a ~eries of lenses 96, selectable color filters 98 and heat absorber 100 to an illumination source 102, ~uch as a 100 watt tungsten-halogen lamp. Fiber optic cable 94 is routed through the tonometric catheter lumen in a fashion similar to the conductor 56 of the above-described embodiments, with the end thereof protruding through the tubing and into the ~ampling chamber 40. A second fiber optic cable 104 is routed parallel to the fir6t fiber optic cable 94, with one end protruding through the tubing and held in place adjacent the end of first cable 94 with a collar 106. Collar 106 may be adhesively bonded to the outside wall of the tubing. The opposite end of second fiber optic cable 104 is positioned for optically coupling with a phototransistor 108 which is electrically connected to an operational amplifier circuit 110.
The operational amplifier circuit can be coupled to an analog to digital converter, 6uch as A/D converter 170 of Figure 7.
In use, fiber optic cable 94 illuminates a region within the ~ampling chamber 40 which is filled with a sampling fluid containing a colorimetric pH indicator. The illumination from fiber optic cable 94 reflects from the molecules ~uspended in the pH indicator ~olution, with some of the reflected illumination passing back through second fiber optic cable 104 to the phototransistor. By selecting the appropriate filter 98, a monochromatic illumination or illumination of otherwise known spectral content is employed to illuminate the colorimetric pH
indicator solution. When the color of the filtered illumination matches that of the indicator, the illumination is absorbed and a low illumination signal is received at the phototransistor. When a pH change causes a color change in the indicator away from the color of the filtered illumination, more illumination is reflected back to the phototransistor, with an attendant increase in detected signal output. In this fashion, the proper selection of indicator dye and illumination filtration can be used to detect pH ranges. For a further description of fiber optic pH
sensor technology, refer to G. G. Vurek "A Fiber Optic PC02 Sensor," Annals of Biomedical Engineering, Vol. 11, pp. 499-510, 1983, which is available from Pergamon Press, Ltd.
While the preferred embodiments have been disclosed in connection with monitoring of the gastrointestinal tract and the urinary and ureteric tracts it will be appreciated that its principles are applicable to other hollow internal organs to monitor pH and hence perfusion of those organs. Also while several presently preferred detailed constructions for tonometric catheters have been disclosed, it will be appreciated that other constructions may be developed which are equally suitable. The disclosed constructions are presently preferred for the reason that they are readily fabricated using existing available materials. Other embodiments may include other, but equivalent materials for the tonometric catheter membrane and/or connective tubing. They may also differ in the specific fabrication details. As an example, the sampling chamber may be eccentric rather than symmetric about the connective tubing.
In still another embodiment, conventional gas analyzers may be employed externally. A device such as that shown in Figure 1 may be used in combination with a pump or aspiration means (not shown) for continuous or regular intermittent aspiration of a sample of the aspirating liquid or medium that is used to fill the sampling chamber 40. The sample removed by pump or aspiration means via attachment to the luer-lock 24 can be optionally designed 80 that the sample aspirated at each 6ampling interval can be brought in contact with an exterior, ~eparate gas analyzing means or sensor (not shown) to determine the pH, pO2~
PCO2 and/or the like, of the sample. Such automatic campling can be conducted employing a system as shown in Figure 12. In the assembly a sampling system employs a personal computer to conduct evaluations and analysis of the 6amples withdrawn from the tonometric catheter 299.
Pump 203 is loaded with the ~ampling or aspirating medium such as ~aline. Next, valve 201 iB activated to withdraw a desired amount of the 6ampling fluid. The valve 201 is deactivated and pump 203 is used to enforce the sampling chamber of the tonometric catheter 299 using a calibrated amount or optionally a pressure transducer 215. The sampling fluid or medium i8 allowed to come to equilibrium with the wall of the organ or area of interest. Next the "dead space," i.e., the area of the lumen filled with the ~ampling fluid that is not in equilibrium, i6 removed by activating valve 20S, activating pump 207, activating valve 209 and infusing pump 207; the waste 219 is discarded. A 6ample for analysis is then withdrawn by deactivating valve 209, activating pump 207 to then deliver the sampling to a gas analyzer (not shown) that provides data from the 6ample to the PC 217, and the evaluation iB conducted as described herein.
~ 33571 0 The sample gas analyzer or a separate gas analyzer may be employed to determine the bicarbonate concentration in the arterial blood of the patient, as described above.
Another embodiment of the tonometric catheter is illustrated in Figures 11 and llA. As illustrated, the tonometric catheter is appropriately configured to also serve as a urinary or ureteric catheter, either with or without suction, which optionally employs sensors. With reference to Figures 11 and llA, the tonometric catheter 220 comprises a multipassage tubing 262 which defines three individual noncommunicating (between each other) passageways or lumens, an optional air or irrigation lumen 264, a drainage or suction lumen 266 and a tonometric catheter lumen 268. A tonometric catheter membrane, ~imilar to that previously described, is attached at a distal location on tubing 262, allowing an intermediate portion of the tubing not extending beyond the end of membrane 236 to define the uretary or uretary catheter 270. Tubing 262 is provided with a plurality of perforations 272 which communicate between tonometric catheter lumen 268 and the ~ampling chamber 240 defined by,membrane 236. If desired, one or more sensors 242 can be included in accordance with the above teachings, in which case a suitable conductor 256 may be routed through tonometric catheter lumen 268 to exit at sealed aperture 258.
The urinary catheter or ureteric catheter portion 270 is suitably provided with a plurality of openings 274 through which the bladder or ureters may be aspirated or irrigated.
At the opposite end of tubing 262 the tubing splits to form three ~eparate connections. Air or irrigation lumen 264 optionally communicates with air lumen passageway 276, urinary - 1 335 7 ~ O
lumen connects with suction or drainage lumen passageway 278 and tonometric catheter lumen 268 communicates with tonometric catheter lumen passageway 280. The tonometric catheter lumen passageway is fitted with three-way stopcock 230, similar in function and purpose to the three-way stopcock 30 described in çonnection with ~igure 1. If desired, a quick connect fitting 82 as seen in Figure 4 may be used to couple the ~uction urinary passageway 278 with an aspiration source. As illustrated, the quick connect fitting preferably has angularly cut ends and a slightly enlarged midsection, making it easy to insert into the end of passageway 278 and also into the aspiration hose coupling (not shown). The enlarged midsection helps form a seal with the adjoining passageways. Preferably the quick connect fitting is fabricated of disposable plastic.
Yet another embodiment of the urinary catheter/tonometric catheter combination illustrated in Figures 11 and llA may employ a multiple tonometric catheter embodiment employing a tubing having a plurality of passageways or lumen as shown in the cross-sectional view of Figure 5A.
In another embodiment of the present invention, a tonometric catheter may be adopted to deliver a pharmaceutically-active agent, either for systemic, local or topical activity, or a combination thereof. For example, an additional lumen may be added such as that and for irrigation or aspiration, to deliver the active. ~or example, the irrigation/aspiration lumen 264 ~hown in Figure 11 and llA, may be used to deliver an active agent. In another embodiment, a portion of the device may be modified so as to provide sustained release of the active agent of interest.
Thus, for example, the problems of nosacomial infection associated with catheter insertion can be overcome by incorporating an antimicrobial into at least a portion of the polymeric material used to manufacture the tonometric catheter, or by coating at least a portion of the device with a sustained release composition, or by delivering the antimicrobial via the tonometric catheter. Such modifications are well known to those skilled in the art. See U.S. Patent No. 4,677,143.
Classes of useful agents include antimicrobial agents, nonsteroidal anti-inflammatory agents, topical anesthetics, topical vasodialators, metabolic suppressants, and other agents that could be delivered for absorption at the ~ites of the tonometric catheter.
Accordingly, while several preferred embodiments of the invention have been disclosed, it will be appreciated that principles of the invention, as set forth in the following claims, are applicable to other embodiments.
Baclcqround, and ~3umm~ry of the Invention This invention relates to medical diagnostic equipment and methods and is particularly concerned with hollow viscus tonometry and remote electronic and optical sensing.
The prior art (see U.S. Patent No. 4,643,192) has recognized that intestinal ischemia, and to a lesser degree, stress ulceration, are two problems that plague physicians involved in the management of patients in intensive care units.
Intestinal ischemia, in particular, has an insidious onset and may not be detected until days after the intestine has become completely and irreversibly compromised. A delay in the diagnosis of intestinal ischemia may have devastating consequences for a patient. The availability of means for early diagnosis and management of patients with these problems would have immediate applicability in all intensive care units, especially where the procedure can be conveniently conducted with reasonable safety and reliability.
It has been established that a fall in the intramucosal pH may precede the development of intestinal ischemia and stress ulceration. As I reported in my prior U.S. Patent No. 4,643,192, entitled "Hollow Viscus Tonometry" a fall in intramucosal pH also occurs within minutes of inducing intestinal ischemia in dogs. The fall in pH
in intestinal mucosa, and hence the likelihood of ischemia or stress ulceration, can be reliably calculated from a PC02 (partial pressure of C02), or other indicia of pH, in luminal fluid and the bicarbonate concentration in arterial blood. The -t ~, '"7, 1 3357 ~ O
method of calculating the pH in intestinal mucosal tissue, pursuant to principles of my prior patent, has been validated by directed measurements under a variety of conditions simulating clinical problems. A correlation coefficient in the order of 0.92 to 0.95 has been obtained in each of 16 dogs. The validity of the procedure is inherently extensible to humans, and indeed may also be useful in assessing the vitality of other hollow organs and tissue. See R.G. Fiddian-Green et al. "Splanchnic Ischemia and Multiple Organ Failure".
To measure the PC2 in the lumen of the gut it has heretofore been necessary to obtain and remove a sample of fluid that has been in contact with the wall of the gut for a certain time period, usually at least half an hour. It has now been observed that it is somewhat difficult to manually aspirate the sampling fluid or medium from a tonometric catheter located in the gut or other internal focus with any consistency. It is much easier to obtain ~uch samples from the stomach, but samples obtained from the stomach frequently contain foreign material that can damage a gas analy~er.
, As taught in my prior patent, the desired sample or samples can be obtained from the gut using a catheter tube (called a tonometric catheter) having a walled sampling chamber on the tube with the sampling chamber being in sample-specific communication with the hollow interior of the tube. The wall of the sampling chamber comprises a material which is substantially impermeable to liquid yet is highly permeable to gas. One suitable material is polydimethylsiloxane elastomer.
In use the catheter is introduced into a patient to place the sampling chamber at a desired site within the gut. An - ~ 3357 1 0 aspirating liquid or medium is employed to fill the interior of the sampling chamber. The sampling chamber is left in place at the desired sampling site long enough to allow the gases present to diffuse through the wall of the ~ampling chamber into the aspirating liquid. The time should be long enough for the gases to equilibrate. The liquid impermeable nature of the sample chamber wall material prevents both the aspirating liquid from leaking out of the chamber and also the intrusion of any liquids into the aspirating liquid. After the appropriate or desired amount of placement time has elapsed the aspirating liquid is aspirated along with the gases which have diffused into it. The sample thus obtained is analyzed for gas content, in particular for pC02. In this way the PC02 within the lumen of the gut can be reliably measured with the fluid being free from lumenal debris.
In carrying out the diagnostic method taught in my prior patent the PC02 measurement is utilized in conjunction with a measurement of the bicarbonate ion concentration (HC03 ) in an arterial blood sample of the patient for determining the pH of the tract wall.
Depending upon the particular condition of a given patient, the catheter may be left in place and samples may ~e taken at periodic intervals so that pH values may be periodically calculated. The procedure has a high reliability in accurately determining the adequacy of organ tissue oxygenation, and diagnosing intestinal ischemia in its incipient ~tages. Such determination or detection can be useful in treating the patient so that the potentially devastating consequences resulting from less timely detection may often be avoided.
While the sampling techniques taught in my prior patent have provided highly accurate and reliable results, it has now been observed that there are instances (in the care of the critically ill in intensive care units, for example) in which remote sensing of the organ or organ-wall condition and automatic calculation of the organ or organ-wall pH would be advantageous and easier to effectuate. This method would thus partially or totally eliminate the need for the somewhat cumbersome aspiration of the sampling fluid or medium which fills the sampling chamber;
it may also eliminate the need for the sampling chamber to be in ~ampling-medium communication with any other part of the device.
There is also a need to extend the benefits of tonometric ~ampling and ~ensing to other internal hollow viscous organs. To this end, there is a need for new and different tonometric devices specifically adapted to allow my sensing and ~ampling techniques to be performed with ease in a clinical environment, and in combination with other procedures.
The importance and ~ignificance of determining the pH
of the wall of a given hollow viscous organ has been recently dràmatically magnified as a result of the recent recognition that the pH of the wall of a given organ can be employed to accurately evaluate the vitality and/or stability of that organ as well as others: this is in contrast to merely determining whether such an organ is experiencing an ischemic event. Further, certain organs can be selected for monitoring, either alone or in combination, and evaluation of this organ or these organs can aid in predicting the overall condition of the patient, or the onset of a multitude of pathologies, including predicting or identifying such events as multiple organ failure. Such a methodology can be employed to greatly enhance and 6upplement the monitoring of the critically ill, for example.
In one aspect, the present invention provides a new apparatus and method for remotely 6ensing organ condition and conveying an electromagnetic signal, e.g. an electrical current or optical ~ignal, to an electronic or optical apparatus located outside the organ under investigation. In one embodiment, a chemically sensitive electronic transducer (or plurality of transducers), 6uch as a field effect transistor, is attached to a tonometric catheter for introduction into the organ along with the tonometric catheter. The first electronic sensor, preferably non-temperature, generates and conveys an electromagnetic signal indicative of some desired aspect of organ condition, e.g., indicative of the pC02, pH and/or P02 level of the organ or organ-wall. For example, in one preferred embodiment, mean ambient pC02, pH and/or P2 f lumenal fluid or the like is measured or monitored via wire or other suitable electromagnetic energy conveying means to an electronic circuit which interprets the electromagnetic signal and produces a report of the organ condition. ! The electronic circuit may include an input for receiving a separately determined signal indicative of the blood pH of the patient. Using this pC02, pH and/or P02 measurement along with blood (preferably arterial) pH data, the electronic circuit determines the pH of the organ wall under test and thereby provides information for determining the organ's current condition or perhaps predicting the organ's future condition.
The electronic circuit may be suitably constructed from analog components, digital components or both.
In another embodiment, a pH, PC02 or P02 sensitive colorimetric substance is injected into an area adjacent to the organ, e.g., into the sampling chamber of the tonometric catheter, and an optical sensor is employed to detect color change in order to determine the pH of the wall of that organ.
The optical sensor can either be disposed in or on the tonometric catheter for introduction into the area adjacent the organ or it may be disposed outside the organ with fiber optic cable optically coupling the sensor to the tonometric catheter site at which the pH sensitive substance has been injected.
In another aspect the present invention provides a variety of new and different tonometric catheter devices for sensing and/or sampling a fluid or gas property (such as pH, P02, pC02, and the like) which is indicative of the condition of an internal organ, in conjunction or combination with a walled catheter tube adapted for delivery or draining fluids, such as nasogastric tubes, urinary catheters, ureteric catheters, intestinal feeding tubes, wound or abdominal drains (suction or regular) and biliary tubes, catheters and stents, with or without remote sensing means for pH, PC02 and/or Po2-In still another aspect or embodiment, the deviceemploys two separate walled catheter tubes, one tonometric catheter tube for the measurement of a fluid or gas property, that is in communication with the sampling chamber; and a second walled catheter tube adapted for delivering or draining fluids.
In yet another aspect or embodiment, the device employs a walled sampling chamber in communication with a sensing means, and a second walled catheter tube adapted for delivering or draining fluids.
1 33 ~7 1 ~
Optionally, when a non-temperature sensing-means is employed, a second sensing-means may be employed as well.
For a more complete understanding of the invention, its objects and advantages, reference may be had to the following specification and to the accompanying drawings. Also, see applicant's co-pending Canadian applications filed of even date herewith entitled "Hollow Viscus and Solid Organ Tonometry" and "Tonometric Catheter Apparatus", bearing respective serial numbers 609,066 and 609,065.
~rief Description of the Drawinqs Figure 1 is a plan view of a first embodiment of the tonometric catheter;
Figure 2A is a partial cross-sectional view of the tonometric catheter illustrating a first means for attachment of an electronic field effect transistor sensor;
Figure 2B is a partial cross-sectional view of the tonometric catheter illustrating a second means of attachment of the field effect transistor sensor;
Figure 3 illustrates the method of use of the tonometric catheter in measurement of the pH of the colon and also of the stomach, the specific embodiment illustrated for colonic measurement being that of Figure 5 and the specific tonometric catheter for gastric measurement being that of Figure 4;
Figure 4 is another embodiment of the tonometric catheter with nasogastric tube;
Figure 4A is a cross-sectional view of the tonometric catheter of Figure 4 taken substantially along the line 4A-4A of Figure 4;
Figure 4B is a cross-sectional view of the tonometric catheter of Figure 4 taken substantially along the line 4B-4B of Figure 4;
Figure 5 is yet another embodiment of the tonometric catheter having multiple sensing/6ampling portions;
Figure 5A is a cross-sectional view of the tonometric catheter of Figure 5, taken substantially along the line 5A-5A of Figure 5;
Figure 6 is a detailed view illustrating the tonometric catheter of Figure 4 in use within the stomach;
Figure 7 is a detailed vieW illustrating the tonometric catheter of Figure 5 in use within the colon;
Figure 8 is a similar view illustrating the tonometric catheter of Figure 1 in use within the colon;
Figure 9 is an electrical schematic diagram illustrating one embodiment of electronic circuit in accordance with the invention;
Figure 10 is an electrical schematic diagram illustrating another embodiment of the optical measurement of pH
in accordance with the invention;
Figure 11 is another embodiment of a tonometric catheter with a urinary catheter;
Figure llA is a cross-sectional view of the tonometric catheter/urinary catheter of Figure 11, taken substantially along the line llA-llA of Figure 11.
t 1 3357 ~ ~
De~cript~on of the Preferred Embodiment~
Figure 1 illustrates a first embodiment of tonometric catheter 20. The tonometric catheter comprises a length of suitable tubing 22, one end 32 of which is closed, and the opposite end of which has a connector such as a luer-lock 24.
Luer-lock 24 is adapted to receive a complementary fitting 26, which in turn couples through a ~econd length of tubing 28 to a three-way stopcock 30. Three-way ~topcock 30 may be used to selectively connect tubing 28 to various sources of irrigation or aspiration.
Adjacent the closed end 32, tubing 22 is perforated as at 34. A balloon-like tonometric catheter membrane 36 is fitted over the closed end ~o that the perforations 34 are enclosed, as illustrated. The tonometric catheter membrane 36 has an internal sleeve diameter at 38 which forms a tight fit with tubing 22.
The preferred form of tonometric catheter membrane is polydimethylsiloxane elastomer. The membrane may be sealed to the tubing 22 with appropriate adhesive so that the tonometric catheter membrane is ~ealed in a closed relationship to the outer wall of tubing 22, thereby forming a ~ampling chamber 40 adjacent closed end 32. The tonometric catheter membrane has a certain elasticity to allow the membrane to expand when filled with an aspirating liquid in order to contact the wall of the organ under examination, as will be explained below.
The membrane 36 is preferably constructed such that at least a portion of it is selectively permeable to the gas or fluid property of interest. In a preferred embodiment, it is ~electively permeable to hydrogen, oxygen, or H+, ~o that pH, PC02 and/or P02 can be measured. It i~ also preferably impermeable to other materials that would interfere with the desired measurements, such as other gases, proteins, and the like. In a highly preferred embodiment, an ion-selective membrane is employed.
Bonded to either the inner wall or the outer wall of tubing 22 are one or more sensors 42 for detecting a property indicative of pH and/or temperature. Two such sensors are illustrated in Figure 1, bonded to the outside wall of tubing 22 with ~uitable adhesive. Figures 2A and 2B illustrate two alternate means of ~ensor attachment, Figure 2A illustrating the ~ensor attached to the inner wall of tubing 22 and Figure 2B
illustrating the sensor attached to the outer wall of tubing 22.
In a preferred embodiment, at least a portion of the tubing, but not all of it, i~ made of a C02 impermeable material, such as polyester elastomers derived from the reaction of dimethylterephtalate 1,4-butanediol and o-hydro- Q -hydroxypoly (oxytetramethylene). In a highly preferred embodiment, this is a material such as Hytril, sold by DuPont.
For purposes of censing temperature, thermistor devices are presently preferred. For sensing properties indicative of pH
chemically responsive field effect transistors or "Chemfets" may be employed. In this regard, Chemfet ~ensors 44 have been illustrated in Figures 2A and 2B. Chemfet sensor 44 comprises a field effect ~emiconductor device 46, which is encapsulated in a ~olution impervious material 48, such as a polymerized epoxy resin. The encapsulation material 48 in turn may be encapsulated in a housing 50 (Figure 2A). Semiconductor device 46 is electrically coupled by bonding wires 52 to a terminal 54.
Suitable electrical conductors such as conductor 56 are attached * Trade-mark -- 10 ~
to terminal 54 for electrically communicating between the Chemfet device 44 and the electronic circuitry described below in connection with Figure 9. Conductor 56 is preferably routed through tubing 22 and exits through a sealed aperture at or near the luer-lock end of tubing 22, as at 58. A more detailed description of a cuitable electronic sensor may be found in U.S.
Patent No. 4,020,830 to Johnson, entitled "Selective Chemical Sensitive FET Transducers " In order to allow a solution to contact the chemically sensitive surface of semiconductor device 46, tubing 22 may be provided with an aperture 60 when implementing the embodiment of Figure 2A. Such an aperture is not needed in the embodiment of Figure 2B, Rince the semiconductor device 46 is exposed to sampling chamber 40 by virtue of the external mounting configuration.
The sampling chamber 40 can be filled with an aspiration or sampling medium that is used to absorb or otherwise provide a means for incorporating and delivering or measuring the the fluids or gases of interest. Such a medium is selected depending upon many factors, including the properties of the fluids or gases of interest, the type of censor 42 employed, and the type of calibration that is necessary. Such mediums include bicarbonate solutions and caline solution. It might be noted that gases often behave as fluids and are therefore frequently considered to be fluids.
As noted above, when the ~ensor employed does not require frequent reca'libration, the need for the sampling chamber 40 to be in communication with the proximate end of the tonometric catheter (that remains outside the patient) may be ! i eliminated ~ince no aspiration is needed. However, in many instances ~uch communication may still be desirable as aspiration may be required to calibrate the sensor or ~ensors, to replace the aspirating or ~ampling medium with a fresh medium, and to incorporate the gas or gases of interest.
Another embodiment of the tonometric catheter is illustrated in Figures 4, 4A and 4B. As illustrated, the tonometric catheter is appropriately configured to al60 serve as a nasogastric sump, either with or without gastric suction. With reference to Figure 4, the tonometric catheter 20a comprises a multipassage tubing 62 which defines three individual noncommunicating (between each other) passageways or lumens, an air lumen 64, an optional 6uction lumen 66 and a tonometric catheter lumen 68. A tonometric catheter membrane, similar to that previously described, ifi attached at an intermediate location on tubing 62, allowing a portion of the tubing to extend beyond the end of membrane 36 to define the nasogastric 6ump 70.
Tubing 62 is provided with a plurality of perforations 72 which communicate between tonometric catheter lumen 68 and the sampling chamber 40 defined by membrane 36. If desired, one or more ~ensor~ 42 can be included in accordance with the above teachings, in which case a suitable conductor 56 may be routed through tonometric catheter lumen 68 to exit at sealed aperture 58.
The nasogastric sump portion 70 is ~uitably provided with a plurality of openings 74 through which the stomach may be aspirated.
At the opposite end of tubing 62 the tubing ~plits to form three separate connections. Air lumen 64 communicates with f ~ ~
1 33~7~ 0 air lumen passageway 76, suction lumen connects with suction lumen passageway 78 and tonometric catheter lumen 68 communicates with tonometric catheter lumen passageway 80. The tonometric catheter lumen passageway is fitted with three-way stopcock 30, 6imilar in function and purpose to the three-way stopcock 30 described in connection with Figure 1. If desired, a quick connect fitting 82 may be used to couple the suction lumen passageway 78 with an aspiration source. As illustrated, the quick connect fitting preferably has angularly cut ends and a slightly enlarged midsection, making it easy to insert into the end of passageway 78 and also into the aspiration hose coupling (not shown). The enlarged midsection helps form a seal with the adjoining passageways. Preferably the quick connect fitting is fabricated of disposable plastic.
Yet another embodiment of the tonometric catheter is illustrated in Figures 5 and 5A. This embodiment is a multiple tonometric catheter embodiment employing a tubing 84 having a plurality of passageways or lumen as shown in the cross-sectional vlew of Figure 5A. Specifically, tubing 84 includes an air lumen 86a which communicates with the endmost tonometric catheter 36a and three additional tonometric catheter lumens 86b, 86c and 86d, which communicate respectively with tonometric catheters 36b, 36c and 36d. As with the other embodiments, each tonometric catheter may be provided with one or more 6ensors such as sensor6 42. A radiopaque tungsten plug 88 i6 positioned within each of the three tonometric catheter lumen 86b, 86c and 86d adjacent the distal end of each tonometric catheter, serving to block the remainder of the tonometric catheter lumen passageway and thereby ensuring that fluid pressure introduced into each tonometric catheter lumen will cause the associated tonometric catheter to balloon outwardly as required during use.
Similarly, a radiopaque tungsten rod 90 is fitted as a plug in the end of air lumen 86a, ~erving to terminate the end of the air lumen passageway. Being radiopaque, the tungsten plugs and tungsten rod aid in properly positioning the tonometric catheters by being visible under fluoroscope or x-ray. In addition, if desired, tubing 84 can be provided with a radiopaque stripe along all or part of its length.
At the proximal end of tubing 84 the lumen 86a-86d diverge to define four separate tubes 92a-92d. Each tube is fitted with a three-way stopcock similar to those described above. Each 6ampling connector may optionally be coded numerically by color, etc. While four approximately equally spaced tonometric catheters have been illustrated in Figure 5, it will be understood that the invention can be modified to include a greater or fewer number of tonometric catheters at different spacing as required for a particular application. It will also be understood that 60me or all of the tonometric catheters can include one or more sensors coupled to conductors 56, each preferably routed through the corresponding lumen passageway.
Referring now to Figure 9, a ~uitable electronic monitoring circuit will now be described. In Figure 9 CHEMFET
semiconductor device 46 has been shown schematically by the equivalent circuit model enclosed in dotted lines. The device 46 thus comprises drain electrode 150, source electrode 152 and reference electrode 15i. The chemically selective ~ystem, such as a membrane system is depicted diagrammatically at 156. The substrate is grounded as at 158.
Source electrode 154 is coupled to an input lead of operational amplifier 160 which includès feedback network diagrammatically depicted at 162. Operational amplifier 160 senses the drain source current flowing through device 46 and converts this signal into a voltage signal which is output on lead 164. The drain source current changes in accordance with changes in the chemical ~ystem under test. More specifically, as the PCO2 level changeæ in the fluid exposed to device 46, the drain source current changes accordingly. Hence the output voltage 6ignal on lead 164 is likewise an indication of the PCO2 level of the organ under test. This voltage signal on lead 164 is coupled to an input of comparator 166 which also receives a reference voltage Vref, which may be supplied using a voltage divider network (not shown) or which may alternatively be provided by a digitally controlled voltage source 168. The output of comparator 166 is fed to reference electrode 154 to provide a stable reference bias voltage. If a digitally controlled voltage source is used, this reference voltage can be adjusted and calibrated by a computer circuit yet to be discussed. The voltage signal on lead 164 is also fed to an analog to digital convertor 170, which is in turn coupled to a microprocessor-based microcomputer 172.
In order to automatically determine the pH of the wall of the hollow viscous organ under test, a separate gas analyzer sensor 174 is used to determine the bicarbonate concentration in the arterial blood of the patient. The output of ~ensor 174 is coupled through analog to digital convertor 176 to microcomputer 172. Microcomputer 172 is preprogrammed to calculate the pH of the organ wall using the values provided by 1 3357 ~ O
analog to digital convertors 170 and 176. Conversion of PCO2 measurements can be converted into pH measurements automatically by microcomputer 172 using various equations and references well-known in the art.
Although many different types of output devices may be employed, strip chart recorder 178 and CRT monitor 180 have been illustrated. Strip chart recorder 178 and monitor 180 are coupled as output devices to microcomputer 172. Strip chart recorder 178 offers the advantage of developing an easily readable, permanent record of the fluctuations in organ wall pH.
Monitor 180 offers the advantage of providing digital readout of the pH value as well as displaying the upper and lower excursions of pH fluctuation. If desired, microcomputer 172 can be preprogrammed using keyboard 182 to compare the instantaneous pH
value with doctor-selected upper and lower alarm limits. If the measured instantaneous pH fluctuates outside those limits, microcomputer 172 can sound an alarm to alert hospital staff.
While a single 6emiconductor device 46 has been illustrated in conjunction with the electronic circuit of Figure 9, the circuit may be readily adapted for use with a plurality of 6emiconductor devices in order to measure the pH at different locations substantially simultaneously. In such an embodiment, the data coming from each sensor can be fed to a separate I/O port of microcomputer 172. In the alternative, a single I/O port can be used with the individual input signals being time multiplexed.
As an alternative to electronic pH sensors, the invention may also be practiced using optical sensor technology.
Referring to Figure 10, the presently preferred optical sensor embodiment uses a first fiber optic cable 94 which i8 optically coupled through a ~eries of lenses 96, selectable color filters 98 and heat absorber 100 to an illumination source 102, ~uch as a 100 watt tungsten-halogen lamp. Fiber optic cable 94 is routed through the tonometric catheter lumen in a fashion similar to the conductor 56 of the above-described embodiments, with the end thereof protruding through the tubing and into the ~ampling chamber 40. A second fiber optic cable 104 is routed parallel to the fir6t fiber optic cable 94, with one end protruding through the tubing and held in place adjacent the end of first cable 94 with a collar 106. Collar 106 may be adhesively bonded to the outside wall of the tubing. The opposite end of second fiber optic cable 104 is positioned for optically coupling with a phototransistor 108 which is electrically connected to an operational amplifier circuit 110.
The operational amplifier circuit can be coupled to an analog to digital converter, 6uch as A/D converter 170 of Figure 7.
In use, fiber optic cable 94 illuminates a region within the ~ampling chamber 40 which is filled with a sampling fluid containing a colorimetric pH indicator. The illumination from fiber optic cable 94 reflects from the molecules ~uspended in the pH indicator ~olution, with some of the reflected illumination passing back through second fiber optic cable 104 to the phototransistor. By selecting the appropriate filter 98, a monochromatic illumination or illumination of otherwise known spectral content is employed to illuminate the colorimetric pH
indicator solution. When the color of the filtered illumination matches that of the indicator, the illumination is absorbed and a low illumination signal is received at the phototransistor. When a pH change causes a color change in the indicator away from the color of the filtered illumination, more illumination is reflected back to the phototransistor, with an attendant increase in detected signal output. In this fashion, the proper selection of indicator dye and illumination filtration can be used to detect pH ranges. For a further description of fiber optic pH
sensor technology, refer to G. G. Vurek "A Fiber Optic PC02 Sensor," Annals of Biomedical Engineering, Vol. 11, pp. 499-510, 1983, which is available from Pergamon Press, Ltd.
While the preferred embodiments have been disclosed in connection with monitoring of the gastrointestinal tract and the urinary and ureteric tracts it will be appreciated that its principles are applicable to other hollow internal organs to monitor pH and hence perfusion of those organs. Also while several presently preferred detailed constructions for tonometric catheters have been disclosed, it will be appreciated that other constructions may be developed which are equally suitable. The disclosed constructions are presently preferred for the reason that they are readily fabricated using existing available materials. Other embodiments may include other, but equivalent materials for the tonometric catheter membrane and/or connective tubing. They may also differ in the specific fabrication details. As an example, the sampling chamber may be eccentric rather than symmetric about the connective tubing.
In still another embodiment, conventional gas analyzers may be employed externally. A device such as that shown in Figure 1 may be used in combination with a pump or aspiration means (not shown) for continuous or regular intermittent aspiration of a sample of the aspirating liquid or medium that is used to fill the sampling chamber 40. The sample removed by pump or aspiration means via attachment to the luer-lock 24 can be optionally designed 80 that the sample aspirated at each 6ampling interval can be brought in contact with an exterior, ~eparate gas analyzing means or sensor (not shown) to determine the pH, pO2~
PCO2 and/or the like, of the sample. Such automatic campling can be conducted employing a system as shown in Figure 12. In the assembly a sampling system employs a personal computer to conduct evaluations and analysis of the 6amples withdrawn from the tonometric catheter 299.
Pump 203 is loaded with the ~ampling or aspirating medium such as ~aline. Next, valve 201 iB activated to withdraw a desired amount of the 6ampling fluid. The valve 201 is deactivated and pump 203 is used to enforce the sampling chamber of the tonometric catheter 299 using a calibrated amount or optionally a pressure transducer 215. The sampling fluid or medium i8 allowed to come to equilibrium with the wall of the organ or area of interest. Next the "dead space," i.e., the area of the lumen filled with the ~ampling fluid that is not in equilibrium, i6 removed by activating valve 20S, activating pump 207, activating valve 209 and infusing pump 207; the waste 219 is discarded. A 6ample for analysis is then withdrawn by deactivating valve 209, activating pump 207 to then deliver the sampling to a gas analyzer (not shown) that provides data from the 6ample to the PC 217, and the evaluation iB conducted as described herein.
~ 33571 0 The sample gas analyzer or a separate gas analyzer may be employed to determine the bicarbonate concentration in the arterial blood of the patient, as described above.
Another embodiment of the tonometric catheter is illustrated in Figures 11 and llA. As illustrated, the tonometric catheter is appropriately configured to also serve as a urinary or ureteric catheter, either with or without suction, which optionally employs sensors. With reference to Figures 11 and llA, the tonometric catheter 220 comprises a multipassage tubing 262 which defines three individual noncommunicating (between each other) passageways or lumens, an optional air or irrigation lumen 264, a drainage or suction lumen 266 and a tonometric catheter lumen 268. A tonometric catheter membrane, ~imilar to that previously described, is attached at a distal location on tubing 262, allowing an intermediate portion of the tubing not extending beyond the end of membrane 236 to define the uretary or uretary catheter 270. Tubing 262 is provided with a plurality of perforations 272 which communicate between tonometric catheter lumen 268 and the ~ampling chamber 240 defined by,membrane 236. If desired, one or more sensors 242 can be included in accordance with the above teachings, in which case a suitable conductor 256 may be routed through tonometric catheter lumen 268 to exit at sealed aperture 258.
The urinary catheter or ureteric catheter portion 270 is suitably provided with a plurality of openings 274 through which the bladder or ureters may be aspirated or irrigated.
At the opposite end of tubing 262 the tubing splits to form three ~eparate connections. Air or irrigation lumen 264 optionally communicates with air lumen passageway 276, urinary - 1 335 7 ~ O
lumen connects with suction or drainage lumen passageway 278 and tonometric catheter lumen 268 communicates with tonometric catheter lumen passageway 280. The tonometric catheter lumen passageway is fitted with three-way stopcock 230, similar in function and purpose to the three-way stopcock 30 described in çonnection with ~igure 1. If desired, a quick connect fitting 82 as seen in Figure 4 may be used to couple the ~uction urinary passageway 278 with an aspiration source. As illustrated, the quick connect fitting preferably has angularly cut ends and a slightly enlarged midsection, making it easy to insert into the end of passageway 278 and also into the aspiration hose coupling (not shown). The enlarged midsection helps form a seal with the adjoining passageways. Preferably the quick connect fitting is fabricated of disposable plastic.
Yet another embodiment of the urinary catheter/tonometric catheter combination illustrated in Figures 11 and llA may employ a multiple tonometric catheter embodiment employing a tubing having a plurality of passageways or lumen as shown in the cross-sectional view of Figure 5A.
In another embodiment of the present invention, a tonometric catheter may be adopted to deliver a pharmaceutically-active agent, either for systemic, local or topical activity, or a combination thereof. For example, an additional lumen may be added such as that and for irrigation or aspiration, to deliver the active. ~or example, the irrigation/aspiration lumen 264 ~hown in Figure 11 and llA, may be used to deliver an active agent. In another embodiment, a portion of the device may be modified so as to provide sustained release of the active agent of interest.
Thus, for example, the problems of nosacomial infection associated with catheter insertion can be overcome by incorporating an antimicrobial into at least a portion of the polymeric material used to manufacture the tonometric catheter, or by coating at least a portion of the device with a sustained release composition, or by delivering the antimicrobial via the tonometric catheter. Such modifications are well known to those skilled in the art. See U.S. Patent No. 4,677,143.
Classes of useful agents include antimicrobial agents, nonsteroidal anti-inflammatory agents, topical anesthetics, topical vasodialators, metabolic suppressants, and other agents that could be delivered for absorption at the ~ites of the tonometric catheter.
Accordingly, while several preferred embodiments of the invention have been disclosed, it will be appreciated that principles of the invention, as set forth in the following claims, are applicable to other embodiments.
Claims (42)
1. A method for measuring a fluid or gas property other than temperature which is an indicia of the condition of an internal organ of a human or other mammal in vivo in need of such measurement which comprises:
a) providing a tonometric catheter having;
(i) a tonometric catheter tube;
(ii) a walled sampling chamber; and (iii) sensing means for measuring said fluid or gas property on said tube;
said sampling chamber being optionally in communication with the interior of said catheter tube, the wall of said walled sampling chamber comprising a material which is freely permeable to the gas or fluid property measured by said sensing means but poorly permeable to other gases or fluids which may interfere with said sensing means;
b) introducing said catheter into or adjacent the organ of interest in said human or other mammal so that said sampling chamber is disposed at a sampling site which includes at least a portion of the wall of said organ;
c) leaving the sampling chamber disposed at the sampling site for a length of time sufficient to allow said fluid or gas of interest to diffuse from the organ wall across at least a portion of said wall of said sampling chamber into said sampling chamber;
d) analyzing the concentration of the fluid or gas property of interest in the sampling chamber; and e) calculating the pH of the wall of the organ based upon the concentration of the fluid or gas property of interest.
a) providing a tonometric catheter having;
(i) a tonometric catheter tube;
(ii) a walled sampling chamber; and (iii) sensing means for measuring said fluid or gas property on said tube;
said sampling chamber being optionally in communication with the interior of said catheter tube, the wall of said walled sampling chamber comprising a material which is freely permeable to the gas or fluid property measured by said sensing means but poorly permeable to other gases or fluids which may interfere with said sensing means;
b) introducing said catheter into or adjacent the organ of interest in said human or other mammal so that said sampling chamber is disposed at a sampling site which includes at least a portion of the wall of said organ;
c) leaving the sampling chamber disposed at the sampling site for a length of time sufficient to allow said fluid or gas of interest to diffuse from the organ wall across at least a portion of said wall of said sampling chamber into said sampling chamber;
d) analyzing the concentration of the fluid or gas property of interest in the sampling chamber; and e) calculating the pH of the wall of the organ based upon the concentration of the fluid or gas property of interest.
2. A method according to Claim 1 wherein the fluid or gas of interest is carbon dioxide.
3. A method according to Claim 1 wherein the fluid or gas of interest is oxygen.
4. A method according to Claim 1 wherein the tonometric catheter additionally comprises temperature sensing means in communication with the sampling chamber.
5. A method according to Claim 1 in which the material of the wall of said walled sampling chamber is a polydimethylsiloxane elastomeric material.
6. A method according to Claim 1 wherein at least a portion of said tonometric catheter comprises a material which is toxically-acceptable and totally impervious to the gas of interest.
7. A method according to Claim 6 wherein at least a portion of said tonometric catheters comprises -hydro--hydroxypoly- (oxytetramethylene).
8. A method according to Claim 2 wherein the sensor is a chemical sensitive field effect transistor transducer.
9. A method according to Claim 2 wherein the sensor is located within the sampling chamber.
10. A method according to Claim 4 wherein the temperature-sensing means is located within the sampling chamber.
11. An apparatus for remotely determining the condition of a hollow internal organ comprising:
a tonometric catheter having at least one sampling chamber for introduction into said organ or the area adjacent said organ;
said tonometric catheter having an electronic sensor for developing a signal indicative of the condition of said organ in communication with said sampling chamber; and means coupled to said sensor for conveying said signal to a location outside said organ whereby the condition of said organ may be remotely determined.
a tonometric catheter having at least one sampling chamber for introduction into said organ or the area adjacent said organ;
said tonometric catheter having an electronic sensor for developing a signal indicative of the condition of said organ in communication with said sampling chamber; and means coupled to said sensor for conveying said signal to a location outside said organ whereby the condition of said organ may be remotely determined.
12. An apparatus according to Claim 11 which additionally comprises a temperature sensor in communication with said sampling chamber.
13. An apparatus for determining the pH of a hollow internal organ of a human or other mammal in need thereof comprising:
a tonometric catheter having at least one sampling chamber for introduction into said organ or the area adjacent said organ;
a non-temperature sensor disposed on said tonometric catheter in communication with said sampling chamber for introduction into said organ with said tonometric catheter sampling;
said sensor comprising means responsive to a fluid or gas property indicative of pH and for developing an electromagnetic signal indicative of said fluid or gas property;
and a means responsive to said signal for generating a pH
signal indicative of the pH of said organ.
a tonometric catheter having at least one sampling chamber for introduction into said organ or the area adjacent said organ;
a non-temperature sensor disposed on said tonometric catheter in communication with said sampling chamber for introduction into said organ with said tonometric catheter sampling;
said sensor comprising means responsive to a fluid or gas property indicative of pH and for developing an electromagnetic signal indicative of said fluid or gas property;
and a means responsive to said signal for generating a pH
signal indicative of the pH of said organ.
14. An apparatus according to Claim 13 which additionally comprises a temperature sensor in communication with said sampling chamber.
15. An apparatus for remotely determining and reporting the condition of a hollow internal organ of a mammal comprising:
a tonometric catheter having at least one sampling chamber for introduction into said organ or the area adjacent said organ;
said tonometric catheter having a non-temperature sensor in communication with said sampling chamber for developing a first electromagnetic signal indicative of a fluid pressure condition within said organ;
a means for developing a second electromagnetic signal indicative of the blood pH of said mammal;
means receptive of said first and second signals for generating a third signal indicative of the condition of said organ; and means responsive to said third signal and located outside said organ for reporting said condition of said organ.
a tonometric catheter having at least one sampling chamber for introduction into said organ or the area adjacent said organ;
said tonometric catheter having a non-temperature sensor in communication with said sampling chamber for developing a first electromagnetic signal indicative of a fluid pressure condition within said organ;
a means for developing a second electromagnetic signal indicative of the blood pH of said mammal;
means receptive of said first and second signals for generating a third signal indicative of the condition of said organ; and means responsive to said third signal and located outside said organ for reporting said condition of said organ.
16. An apparatus according to Claim 15 which additionally comprises a temperature sensor in communication with said sampling chamber.
17. An apparatus according to Claim 11 wherein said censor comprises a chemically sensitive electronic transducer.
18. An apparatus according to Claim 13 wherein said sensor comprises a chemically sensitive electronic transducer.
19. An apparatus according to Claim 15 wherein said sensor comprises a chemically sensitive electronic transducer.
20. An apparatus according to Claim 11 wherein said sensor comprises a chemically sensitive field effect transistor transducer.
21. An apparatus according to Claim 13 wherein said sensor comprises a chemically sensitive field effect transistor transducer.
22. An apparatus according to Claim 15 wherein said sensor comprises a chemically sensitive field effect transistor transducer.
23. An apparatus according to Claim 13 wherein said electromagnetic signal is an electrical signal conveyed by wire to said means for generating a pH signal.
24. An apparatus according to Claim 15 wherein said first electromagnetic signal is an electrical signal conveyed by wire to said means for generating said third signal.
25. An apparatus according to Claim 15 wherein said means for reporting said condition includes analog circuit means for producing a report of said condition.
26. An apparatus according to Claim 15 wherein said means for reporting said condition includes digital circuit means for producing a report of said condition.
27. An apparatus according to Claim 15 wherein said tonometric catheter additionally comprises a second electronic sensor for determining the temperature of the sampling area adjacent said first sensor.
28. An apparatus according to Claim 15 wherein the fluid or gas property of interest is pCO2.
29. An apparatus according to Claim 15 wherein the fluid or gas property of interest is pO2.
30. An apparatus according to Claim 11 wherein at least a portion of the tonometric catheter comprises .alpha.-hydro- .OMEGA. -hydroxy-poly (oxytetramethylene).
31. A tonometric catheter apparatus for measuring a liquid fluid or gaseous fluid property indicative of the condition of an internal organ of a human or other mammal in vivo, comprising:
(a) an elongated tonometric catheter tube having at least one lumen extending longitudinally therethrough;
(b) at least one walled sampling chamber on said catheter tube in fluid communication with the interior of said lumen, said walled sampling chamber generally surrounding a portion of said catheter tube and being sealingly interconnected therewith, at least a portion of the wall of said sampling chamber being composed of a wall material that is freely and selectively permeable to one or more liquid fluids or gaseous fluids of interest, said wall material being substantially impermeable to other liquid fluids or gaseous fluids, and said sampling chamber forming an interior space with said catheter tube in order to allow said one or more liquid fluids or gaseous fluids of interest from the tissue of the wall portion of the internal organ to permeate into said sampling chamber, with said catheter tube extending to a position outside of the body of the human or other mammal, and with said lumen providing fluid communication between said sampling chamber and the outside of the body of the human or other mammal for a sampling medium to flow therebetween; and (c) analyzing sensor means positioned outside of the body of the human or other mammal and in communication with said lumen, for sensing the level of at least one of said liquid fluids or gaseous fluids of interest permeated from the tissue of the wall portion of the internal organ with said sampling medium in sampling chamber.
(a) an elongated tonometric catheter tube having at least one lumen extending longitudinally therethrough;
(b) at least one walled sampling chamber on said catheter tube in fluid communication with the interior of said lumen, said walled sampling chamber generally surrounding a portion of said catheter tube and being sealingly interconnected therewith, at least a portion of the wall of said sampling chamber being composed of a wall material that is freely and selectively permeable to one or more liquid fluids or gaseous fluids of interest, said wall material being substantially impermeable to other liquid fluids or gaseous fluids, and said sampling chamber forming an interior space with said catheter tube in order to allow said one or more liquid fluids or gaseous fluids of interest from the tissue of the wall portion of the internal organ to permeate into said sampling chamber, with said catheter tube extending to a position outside of the body of the human or other mammal, and with said lumen providing fluid communication between said sampling chamber and the outside of the body of the human or other mammal for a sampling medium to flow therebetween; and (c) analyzing sensor means positioned outside of the body of the human or other mammal and in communication with said lumen, for sensing the level of at least one of said liquid fluids or gaseous fluids of interest permeated from the tissue of the wall portion of the internal organ with said sampling medium in sampling chamber.
32. An apparatus according to Claim 31, wherein said walled sampling chamber is defined by a balloon member generally surrounding a portion of said catheter tube and sealingly interconnected therewith, the wall of said balloon member being composed of said wall material that is freely permeable to said one or more liquid fluids or gaseous fluids of interest and substantially impermeable to other liquid fluids or gaseous fluids, said balloon member being deformable for forming said interior space with said catheter tube.
33. An apparatus according to Claim 31, wherein said walled sampling chamber is defined by an opening in said catheter tube, said opening being covered by said wall material sealingly interconnected with said catheter tube substantially adjacent said opening.
34. An apparatus according to Claim 33, wherein said wall material is deformable.
35. A tonometric catheter apparatus for measuring a liquid fluid or gaseous fluid property indicative of the condition of an internal organ of a human or other mammal in vivo, comprising:
(a) an elongated tonometric catheter tube having at least one lumen extending longitudinally therethrough;
(b) at least one walled sampling chamber on said catheter tube in fluid communication with the interior of said lumen, said walled sampling chamber being defined by a balloon member generally surrounding a portion of said catheter tube and being sealingly interconnected therewith, at least a portion of the wall of said balloon member being composed of a wall material being substantially impermeable to other liquid fluids or gaseous fluids, and said balloon member being inflated for forming an interior space between said balloon member and said catheter tube in order to allow said one or more liquid fluids or gaseous fluids of interest from the tissue of the wall portion of the internal organ to permeate into said sampling chamber, with said catheter tube extending to a position outside of the body of the human or other mammal, and with said lumen providing fluid communication between said sampling chamber and the outside of the body of the human or other mammal for a sampling medium to flow therebetween; and (c) analyzing sensor means positioned outside of the body of the human or other mammal in communication with said lumen, for sensing the level of at least one of said liquid fluids or gaseous fluids of interest permeated from the tissue of the wall portion of the internal organ into said sampling medium in said sampling chamber.
(a) an elongated tonometric catheter tube having at least one lumen extending longitudinally therethrough;
(b) at least one walled sampling chamber on said catheter tube in fluid communication with the interior of said lumen, said walled sampling chamber being defined by a balloon member generally surrounding a portion of said catheter tube and being sealingly interconnected therewith, at least a portion of the wall of said balloon member being composed of a wall material being substantially impermeable to other liquid fluids or gaseous fluids, and said balloon member being inflated for forming an interior space between said balloon member and said catheter tube in order to allow said one or more liquid fluids or gaseous fluids of interest from the tissue of the wall portion of the internal organ to permeate into said sampling chamber, with said catheter tube extending to a position outside of the body of the human or other mammal, and with said lumen providing fluid communication between said sampling chamber and the outside of the body of the human or other mammal for a sampling medium to flow therebetween; and (c) analyzing sensor means positioned outside of the body of the human or other mammal in communication with said lumen, for sensing the level of at least one of said liquid fluids or gaseous fluids of interest permeated from the tissue of the wall portion of the internal organ into said sampling medium in said sampling chamber.
36. A method of measuring a liquid fluid or gaseous fluid property indicative of the condition of an internal organ of a human or other mammal in vivo, comprising the steps of:
(a) providing an elongated tonometric catheter tube having at least one lumen extending longitudinally therethrough with at least one walled sampling chamber on said catheter tube in fluid communication with the interior of said lumen, said walled sampling chamber generally surrounding a portion of said catheter tube and being sealingly interconnected therewith, the wall of said sampling chamber being composed of a wall material that is freely and selectively permeable to one or more liquid fluids or gaseous fluids of interest, said wall material being substantially impermeable to other liquid fluids or gaseous fluids said sampling chamber defining an interior space between said sampling chamber and said catheter tube;
(b) providing a gas analyzing apparatus for sensing the level of at least one of said liquid fluids or gaseous fluids of interest;
(c) introducing the catheter tube into the organ of interest so that said walled sampling chamber is disposed at a desired sampling site, said catheter tube extending to a position outside the body of the human or other mammal so that said lumen provides fluid communication between said sampling chamber and the outside of the body of the human or other mammal;
(d) introducing a sampling medium into said catheter tube and into said interior space between said sampling chamber and said catheter tube;
(e) leaving said sampling chamber disposed at said sapling site for a length of time sufficient to allow said liquid fluid or gaseous fluids of interest that are present at said sampling site to diffuse across the wall of the sampling chamber into said sampling medium contained within said sampling chamber;
(f) withdrawing at least a portion of said sampling medium through said catheter tube; and (g) analyzing the sample thus withdrawn using said gas analyzer means to determine the level present of said liquid fluid or gaseous fluid in said withdrawn sampling medium.
(a) providing an elongated tonometric catheter tube having at least one lumen extending longitudinally therethrough with at least one walled sampling chamber on said catheter tube in fluid communication with the interior of said lumen, said walled sampling chamber generally surrounding a portion of said catheter tube and being sealingly interconnected therewith, the wall of said sampling chamber being composed of a wall material that is freely and selectively permeable to one or more liquid fluids or gaseous fluids of interest, said wall material being substantially impermeable to other liquid fluids or gaseous fluids said sampling chamber defining an interior space between said sampling chamber and said catheter tube;
(b) providing a gas analyzing apparatus for sensing the level of at least one of said liquid fluids or gaseous fluids of interest;
(c) introducing the catheter tube into the organ of interest so that said walled sampling chamber is disposed at a desired sampling site, said catheter tube extending to a position outside the body of the human or other mammal so that said lumen provides fluid communication between said sampling chamber and the outside of the body of the human or other mammal;
(d) introducing a sampling medium into said catheter tube and into said interior space between said sampling chamber and said catheter tube;
(e) leaving said sampling chamber disposed at said sapling site for a length of time sufficient to allow said liquid fluid or gaseous fluids of interest that are present at said sampling site to diffuse across the wall of the sampling chamber into said sampling medium contained within said sampling chamber;
(f) withdrawing at least a portion of said sampling medium through said catheter tube; and (g) analyzing the sample thus withdrawn using said gas analyzer means to determine the level present of said liquid fluid or gaseous fluid in said withdrawn sampling medium.
37. A method of measuring a liquid fluid or gaseous fluid property indicative of the condition of an internal organ of a human or other mammal in vivo, comprising the steps of:
(a) providing an elongated tonometric catheter tube having at least one lumen extending longitudinally therethrough with at least one walled sampling chamber on said catheter tube in fluid communication with the interior of said lumen, said walled sampling chamber being defined by a balloon member generally surrounding a portion of said catheter tube and being sealingly interconnected therewith, the wall of said balloon member being composed of a wall material that is freely and selectively permeable to one or more liquid fluids or gaseous fluids of interest, said wall material being substantially impermeable to other liquid fluids or gaseous fluids, said balloon member defining an interior space between said sampling chamber and said catheter tube;
(b) providing a gas analyzing apparatus for sensing the level of at least one of said liquid fluids or gaseous fluids of interest;
(c) introducing the catheter tube into the organ of interest so that said balloon member is disposed at a desired sampling site, said catheter tube extending to a position outside the body of the human or other mammal so that said lumen provides fluid communication between said balloon member and the outside of the body of the human or other mammal;
(d) introducing a sampling medium into said catheter tube and into said interior space between said balloon member and said catheter tube;
(e) leaving said sampling chamber disposed at said sampling site for a length of time sufficient to allow said liquid fluids or gaseous fluids of interest that are present at said sampling site to diffuse across the wall of the balloon member into said sampling medium contained within said balloon member;
(f) withdrawing at least a portion of said sampling medium through said catheter tube; and (g) analyzing the sample thus withdrawn using said gas analyzer means to determine the level present of said liquid fluid or gaseous fluid in said withdrawn sampling medium.
(a) providing an elongated tonometric catheter tube having at least one lumen extending longitudinally therethrough with at least one walled sampling chamber on said catheter tube in fluid communication with the interior of said lumen, said walled sampling chamber being defined by a balloon member generally surrounding a portion of said catheter tube and being sealingly interconnected therewith, the wall of said balloon member being composed of a wall material that is freely and selectively permeable to one or more liquid fluids or gaseous fluids of interest, said wall material being substantially impermeable to other liquid fluids or gaseous fluids, said balloon member defining an interior space between said sampling chamber and said catheter tube;
(b) providing a gas analyzing apparatus for sensing the level of at least one of said liquid fluids or gaseous fluids of interest;
(c) introducing the catheter tube into the organ of interest so that said balloon member is disposed at a desired sampling site, said catheter tube extending to a position outside the body of the human or other mammal so that said lumen provides fluid communication between said balloon member and the outside of the body of the human or other mammal;
(d) introducing a sampling medium into said catheter tube and into said interior space between said balloon member and said catheter tube;
(e) leaving said sampling chamber disposed at said sampling site for a length of time sufficient to allow said liquid fluids or gaseous fluids of interest that are present at said sampling site to diffuse across the wall of the balloon member into said sampling medium contained within said balloon member;
(f) withdrawing at least a portion of said sampling medium through said catheter tube; and (g) analyzing the sample thus withdrawn using said gas analyzer means to determine the level present of said liquid fluid or gaseous fluid in said withdrawn sampling medium.
38. An apparatus for analyzing a compound to be drawn from a patient's organism, said apparatus comprising a sampling element, a compound to be analyzed being capable of penetrating its wall and, thus, of transferring from the organism into a sample chamber included in said sampling element, an aspiration means which is capable of carrying a sample from said sample chamber along a tube extending from said sampling element, and a gas analyzer capable of performing the analysis of a sample drawn from said sampling element, characterized in that the analyzer is by way of tube in flow communication with said sampling element.
39. An apparatus according to Claim 38, characterized in that said sample chamber of said sampling element contains some medium for admixing therein a compound coming from the organism into the sample chamber.
40. An apparatus according to Claim 38, characterized in that said gas analyzer is used for analyzing the content of a compound drawn from the organism.
41. An apparatus according to Claim 38, adapted for analyzing the content of carbon dioxide.
42. A method for analyzing a compound to be drawn from a patient's organism, the compound transmitting through a wall included in a sampling element placed in the organism of a patient into a sample chamber included in this element, said chamber containing a medium for admixing the compound therewith, and a sample consisting of said medium and the compound drawn from the organism being delivered away from the sampling element for a subsequent analysis, characterized in that an aspirating element is used for delivering a sample from the sampling element to a gas analyzer, which is in a direct flow communication with the sampling element.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US23728788A | 1988-08-26 | 1988-08-26 | |
| US237,287 | 1988-08-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1335710C true CA1335710C (en) | 1995-05-30 |
Family
ID=22893108
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000609067A Expired - Fee Related CA1335710C (en) | 1988-08-26 | 1989-08-23 | Remote sensing tonometric catheter apparatus and method |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU658067B2 (en) |
| CA (1) | CA1335710C (en) |
| ES (1) | ES2014890A6 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015089417A1 (en) * | 2013-12-12 | 2015-06-18 | Right Biometrics | Fluid characteristic indicator |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2734247C2 (en) * | 1977-07-29 | 1984-07-19 | Fresenius AG, 6380 Bad Homburg | Device for continuous chemical analysis in the living body |
| NL8001420A (en) * | 1980-03-10 | 1981-10-01 | Cordis Europ | ELECTRODE COMPOSITIVE COMPOSITE, FOR AN ELECTROCHEMICAL MEASUREMENT, IN PARTICULAR AN ISFET-CONSTRUCTED COMPOSITION, AND METHOD FOR MANUFACTURING THE ASSEMBLY. |
| US4727730A (en) * | 1986-07-10 | 1988-03-01 | Medex, Inc. | Integrated optic system for monitoring blood pressure |
-
1989
- 1989-08-23 CA CA000609067A patent/CA1335710C/en not_active Expired - Fee Related
- 1989-08-25 ES ES8902941A patent/ES2014890A6/en not_active Expired - Lifetime
-
1993
- 1993-06-10 AU AU40162/93A patent/AU658067B2/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| ES2014890A6 (en) | 1990-07-16 |
| AU658067B2 (en) | 1995-03-30 |
| AU4016293A (en) | 1993-08-19 |
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| MKLA | Lapsed |