IES922955A2 - Pressure indicating syringe attachment - Google Patents

Abstract

The present invention provides a pressure indicating syringe attachment 5 to monitor pressure within a syringe (which is substantially also the pressure in the vein) during injection as excess pressure may lead to damage to the vein or surrounding tissue. The syringe attachment is connectable in line between a syringe barrel and a needle or catheter and has an internal bore (4) through which injectate may pass and a 10 means (7, 20) by which pressure changes in the internal bore are detected and a display means to indicate the pressure detected (9, 12, 16, 19a, 21). The display means can take various forms of a mechanical or electrical nature.

Description

Pressure Indicating Syringe Attachment The present invention relates to a device for monitoring pressure in peripheral veins during manual injection by a hand held syringe. The device allows excess pressure to be detected and remedial action can be taken.

It has long been recognised that injection or infusion into a human vein can cause a variety of medical problems one of which is damage to the tissue caused by the pressure of the fluid being administered.

Many veins are extremely delicate, especially those in the peripheral areas of circulation such as the lower arms and hands. Whilst patients of any age can experience difficulty with their veins as a result of such infusion, those who have a high risk factor are the geriatric, the chronically ill (young & old) and the neonates, or newly born.

The length and material of the catheter, the type of drug administered, the flowrate and the pressure of the infusion are all important factors which may lead to damage to the vein. Should administered fluid escape from the vein, this occurrence is called extravasation. Furthermore, an increased resistance may develop during the period of infusion and is often as a result of vasoconstriction. The position of a patient's arm for instance, the bending of a limb, the formation of a thrombus etc. may cause local constriction and reduce or cut off flow. Where IE 922955 - 2 vasoconstriction totally occludes the vein, the pressure in that vein may become so great as to cause the vein wall to rupture and allow the fluid to flow into the surrounding tissues. This can be extremely painful to the patient, lead to the immediate withdrawal of the cannula or catheter and may take a considerable period to heal.

Most modern infusion pumps used to administer these fluids are fitted with occlusion detectors and will alarm should back pressure be encountered, usually if it exceeds 10 or 12 P.S.I.. However, there appear to be no device to indicate excess pressure, for whatever reason, during injection by hand-held syringes. Such injections are usually made directly into the cannula or catheter (when fitted with a latex membraned injection port) or via a stopcock fitted to the infusion set.

Very considerable and highly damaging pressures in excess of 30 P.S.I. can rapidly develop during such injections, especially if small syringes are used since the smaller the syringe, the less detectable the problem of occlusion can be, as the resistance to the forward movement of the plunger is proportional to its diameter.

The object of this invention therefore is to provide a simple, inexpensive and easy to use integral device to clearly indicate to the nurse or doctor that a pressure build-up is developing whilst the plunger of the syringe is pushed forward during injection into a constricted or occluded vein. If the injection is able to pass without hindrance into the vein and along its pathway, then it is intended that the gauge would register no increase in venous pressure beyond that which is normal (and often known as C.V.P. or Central Venous Pressure). However, in the presence of resistance the device of this invention will indicate the level of excess pressure and the need to take action to prevent damage to the intima of the vein and to the surrounding tissues.

According to the present invention there is provided a pressure indicating syringe attachment connectable in line between an injection syringe barrel and an injection needle or catheter, having an internal bore through which injectate may pass and a means by which pressure IE 922955 - 3 charges in the internal bore are detected and a display means to indicate the pressure detected.

The means by which pressure changes are detected may be a diaphragm.

Movement of the diaphragm is proportional to the pressure in the syringe. The diaphragm is preferably made of an impermeable, leak-proof material and enclosed in a housing. The diaphragm may be made of latex. The housing may comprise a roof and a cylindrical wall and a base, at least a portion of which is formed by the diaphragm.

Preferably the attachment comprises a duct depending from the attachment having an internal bore communicating with the bore of the attachment and a diaphragm sealing the end of the duct remote from the attachment.

The display means to indicate the pressure detected may comprise lines marked on the housing, the housing being substantially transparent such that the extent to which the diaphragm rises in response to pressure in the syringe can be read against a line on the housing. The lines may be marked on the side of the housing and may be colour-coded.

Alternatively, the housing may be shallow enough to allow the dome of the diaphragm to touch the roof thereof and the extent to which the diaphragm flattens out when it touches the roof can be read against a scale marked on the roof.

Alternatively, the attachment may be provided with a pressure guage.

The pressure guage may comprise a pointer and calibrated scale. Suitably, the diaphragm has a plate fixed thereto which is connected to the pointer which in turn is pivotably mounted on the housing such that the pointer moves in response to movement of the diaphragm to indicate a value on the scale.

The display means to indicate the pressure measured may also suitably comprise a reservoir of indicator fluid connected to an elongate tube with a closed end, the tube being positioned on the roof of the housing and the reservoir being responsive to movement of the diaphragm such that as the diaphragm rises pressure is exerted on the reservoir which pushes the indicator fluid into the tube, the roof of the housing being IE 922955 - 4 marked with a graduated scale such that the extent that the indicator fluid moves in the tube can be read off as a pressure reading.

Alternatively, the means to indicate the pressure measured may be an 5 electric transducer which is sensitive to pressure changes in the housing caused by movement of the diaphragm, the transducer being connected to a meter. The transducer may also or alternatively be coupled to a light or buzzer which sounds an alarm. The meter may be battery powered and may suitably be hand held. The meter may be fitted temporarily to the syringe during injection via a spring clamp.

In an alternative embodiment the means by which pressure changes in the internal bore of the attachment may be an electric transducer mounted directly in the internal bore.

The gauges on the pressure indicating means may simply indicate high, medium or low pressures or may be graduated to an actual value in pounds per square inch or other appropriate unit.

The attachment may be provided with ends connectable to conventional Luer connections or Luer-Lock ends on syringes, needles, catheters and the like.

Various embodiments of the invention will now be described with reference to the accompanying drawings in which :Figure la is a side elevation of one embodiment of a syringe attachment according to the invention with a visibly rising diaphragm, Figure lb is a plan view of the attachment of Figure la from above, Figure lc is a pictorial view of the attachment of Figure la, Figure 2 is a view of an alternative embodiment of a syringe attachment in which the display incorporates a pointer and gauge, IE 922955 - 5 Figure 3 shows a further embodiment of a syringe attachment in which an indicator liquid can be seen to move around a circular pathway when displaced by a rising diaphragm, and Figure 4 shows another embodiment of syringe attachment in which the diaphragm is coupled to an electric transducer.

A syringe attachment according to the present invention is designed to be connected between the end of a normal injection syringe and a needle or intravenous catheter which may have an injection port fitted thereto. The pressure in the syringe during injection is substantially that in the vein during injection. Thus when fluid is being injected into a patient, venous pressure can be monitored by the attachment such that in the presence of resistance, an increased level of pressure will be indicated so that action can be taken to prevent damage to the vein and surrounding tissues.

As can be seen in figures la to c, one end of the attachment (1) can be connected to a syringe and the opposite end (2) is adapted to be attached to a needle or catheter. In this embodiment, the attachment consists of a barrel (3) having a bore (4) with a duct (5) depending from the barrel (3), the duct (5) having an internal small diameter bore (6) communicating with the bore (4) of the barrel (3). The diameter of the duct bore (6) is smaller than that of the barrel bore (4). The end of the duct remote from the barrel (3) is sealed with a diaphragm (7) made of an elastic, leak proof material such as latex.

In the embodiment of figure 1 the diaphragm (7) is enclosed in a housing (8), and excess pressure in the syringe will cause the diaphragm to rise up from position A to position B as shown. The housing (8) incorporates colour coded lines (9) which are graduated according to the amount of pressure required to raise the diaphragm (7) to each line (9). Alternatively, the housing (8) may be designed so that when the diaphragm rises it can be seen to flatten out when it hits the roof of the housing (8), thus indicating that the syringe pressure should be reduced. The roof of the housing (8) may also be graduated with lines (9).

IE 922955 - 6 In the embodiment shown in figure 2, the diaphragm (7) is fixed to a plate (10). They may be fixed together by ultrasonic welding or glue or the like means. A second chamber (11) is provided on the housing (8). A pointer (12) is pivotably mounted at one end to a lug (13) in the second chamber (11). The plate (10) is provided with an elongate extension (14) which passes into the second chamber (11) through an aperture (not shown) in the roof between the housing (8) and the chamber (11). The extension (14) terminates in a ring (15) through which the pointer (12) passes. Thus as the diaphragm (7) moves, the plate (10) moves with it and pushes or pulls the pointer (12) as it moves. The chamber (11) is provided with a scale (16) adjacent the free end of the pointer (12) which is graduated and marked with pressure values in the appropriate range. As the diaphragm (7) moves the pointer (12) moves also and indicates the pressure in the syringe (which is also the pressure in the vein) on the scale (16).

An alternative embodiment of the invention is shown in figure 3 in which the diaphragm (7) is enclosed in housing (8) which contains a reservoir (17) of coloured liquid dye. The reservoir (17) is connected to a narrow tube (18) with a closed end (19) which is situated on the roof of the housing (8). As pressure builds up during injection, the diaphragm (7) rises and exerts pressure on the reservoir (17) which pushes the dye along the tube (18). The roof of the housing (8) is graduated to form a scale (19a) such that the distance travelled by the dye in the tube (18) indicates a particular pressure on the scale (19a) Yet another embodiment is shown in figure 4 which is an electric version of the attachment. The diaphragm (7) is enclosed in a housing which also comprises an electric transducer (20) or linear voltage differential transformer which is sensitive to changes in pressure within the housing (8) as a result of movement of the diaphragm (7).

The housing (8) may be formed in two parts which screw together. The transducer (20) is connected to a battery powered meter (21) or display which may be hand-held, or can be connected to the syringe by a syringe retaining means (22). The syringe retaining means (22) may be a spring clamp.

IE 922955 - 7 Syringe attachments in accordance with the present invention can be manufactured in a variety of forms and sizes to allow them to fit standard Luer and Luer-Lock syringes and when fitted with a needle to be used in conjunction with injection ports fitted to T-connectors or Y-connectors on intravenous drip sets.

Further, although the specification refers to a syringe attachment as can be applied to syringes as they are manufactured presently, the invention can also extend to a syringe barrel manufactured to incorporate a pressure sensing device.

Claims (5)

1. A pressure indicating syringe attachment comprising a barrel 5 connectable in line between an injection syringe barrel and an injection needle or catheter having an internal bore through which injectate may pass and a means by which pressure changes in the internal bore are detected and a display means to indicate the pressure detected.

2. A pressure indicating syringe attachment as claimed in claim 1 wherein the means by which pressure change are detected is a diaphragm made of an impermeable, leak-proof material and enclosed in a housing, movement of the diaphragm being proportional to the pressure in the 15 syringe.

3. A pressure indicating syringe attachment as claimed in claim 2 wherein there is provided a duct depending from the attachment having an internal bore communicating with the bore of the attachment and a 20 diaphragm sealing the end of the duct remote from the attachment and display means to indicate the pressure detected comprising lines marked on the housing, the housing being substantially transparent such that the extent to which a diaphragm rises in response to pressure in the syringe can be read against a line on the housing.

4. A pressure indicating syringe attachment as claimed in claim 2 wherein the attachment is provided with a pressure guage having a pointer and calibrated scale, the diaphragm being connected to the pointer such that the pointer moves in response to movement of the 30 diaphragm to indicate a value on the scale.

5. A pressure indicating syringe attachment substantially as described herein with reference to any of Figs, la to lc, and/or Fig. 2 and/or Fig. 3 and/or Fig. 4 of the accompanying drawings.