GB2036565A - Oxygen concentration control - Google Patents
Oxygen concentration control Download PDFInfo
- Publication number
- GB2036565A GB2036565A GB7938944A GB7938944A GB2036565A GB 2036565 A GB2036565 A GB 2036565A GB 7938944 A GB7938944 A GB 7938944A GB 7938944 A GB7938944 A GB 7938944A GB 2036565 A GB2036565 A GB 2036565A
- Authority
- GB
- United Kingdom
- Prior art keywords
- oxygen
- oxygen concentration
- mixer
- patient
- control unit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61G—TRANSPORT, PERSONAL CONVEYANCES, OR ACCOMMODATION SPECIALLY ADAPTED FOR PATIENTS OR DISABLED PERSONS; OPERATING TABLES OR CHAIRS; CHAIRS FOR DENTISTRY; FUNERAL DEVICES
- A61G11/00—Baby-incubators; Couveuses
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61G—TRANSPORT, PERSONAL CONVEYANCES, OR ACCOMMODATION SPECIALLY ADAPTED FOR PATIENTS OR DISABLED PERSONS; OPERATING TABLES OR CHAIRS; CHAIRS FOR DENTISTRY; FUNERAL DEVICES
- A61G10/00—Treatment rooms or enclosures for medical purposes
- A61G10/04—Oxygen tents ; Oxygen hoods
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M2230/00—Measuring parameters of the user
- A61M2230/20—Blood composition characteristics
- A61M2230/205—Blood composition characteristics partial oxygen pressure (P-O2)
Landscapes
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Animal Behavior & Ethology (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Gynecology & Obstetrics (AREA)
- Pediatric Medicine (AREA)
- Pregnancy & Childbirth (AREA)
- Emergency Medicine (AREA)
- Pulmonology (AREA)
- Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)
Abstract
An apparatus for controlling the oxygen concentration in a respirable mixture of air and oxygen issuing from a mixer 6 for delivery to a patient 4 in a chamber such as an incubator 2 includes a device, for example, an intravascular electrode for generating a signal corresponding to the oxygen concentration in the blood of the patient 4. The signal is received by a control unit 12 having a shaft 14 which enters the mixer 6, the angular position of which shaft 14 controls the percentage of oxygen in the gas mixture issuing from the mixer. <IMAGE>
Description
SPECIFICATION
Servo-control of arterial oxygen tension
This invention relates to apparatus for automatically controlling the concentration of oxygen in the output from gas-mixing apparatus, so as to control the arterial oxygen tension in patients breathing the gas.
The control of arterial oxygen tension is particularly important in the case of sick, preterm babies in order to avoid the Scylla of hypoxia and the Charybdis of hyperoxia.
When the arterial oxygen tension is continuously monitored in sick, preterm babies, marked fluctuations in it can be seen to occur in short periods, although intermittent analysis of the blood gas may indicate a steady state of the oxygen tension. Such fluctuations may occur spontaneously, or as a result of routine nursing or other procedures. Changes in oxygen tension, together with alterations in heart rate and blood pressure may be an additional cause of perinatal morbidity. The correction of these fluctuations by the manual adjustment of the inspired oxygen concentration requires constant observation and consumes both time and manpower.
The present invention aims at providing apparatus which automatically keeps the arterial oxygen ten- sion of patients within chosen limits for a greater proportion of time than with manual control.
According to the present invention, an apparatus for controlling the oxygen concentration in a respirable mixture of air and oxygen issuing from a gas mixer for delivery to a patient, comprises a device for generating a signal corresponding to the oxygen concentration in the blood of the patient connected to the device, an control unit adapted to receive the signal and to alter the oxygen concentration in the respirable gas issuing from the mixer in one or more discrete amounts when the signal exceeds a preselec ted limit.
The present invention will now be described by way of example with reference to the accompanying drawing, in which:
Figure 1 is a diagrammatic view of the apparatus of the present invention used for monitoring and controlling the arterial oxygen tension in a preterm baby, and
Figure 2 is the curve of current (I) against voltage (V) obtained in the oxygen sensor included in the apparatus shown in Figure 1.
The apparatus shown in Figure 1 includes a chamber of incubator 2 containing the patient 4. The incubator is intended to be supplied under pressure with a mixture of air and oxygen issuing from a mixer 6 adapted to receive separate supplies of air and oxygen through inlets 8. The incubator 2 is vented to atmosphere through the normal gaps in its construction, because it is not designed to be gastight.
A control unit 12 is coupled to the mixer through a shaft 14, the angular position of which controls the percentage of oxygen in the gas mixture passing to the incurator 2. The shaft 14 is connected to a servomotor so that the shaft is able to be driven through steps, with the size of each step (or angular rotation of shaft 14) being such that it results in a 5% change in the oxygen concentration.
The control unit 12 is intended to be responsive to the arterial oxygen tension in the patient 4, as sampled either by means of an intravascular electrode, for example, an indwelling umbilical catheter-tip electrode, ortranscutaneously using a heated skinsurface electrode. The electrode is connected to any oxygen meter included in the control unit. The reading of the meter is checked at least every four hours by a formal blood gas analysis, and adjustment made as necessary.
The control unit 12 has knobs (not shown) or other devices by means of which the upper and lower limits for the arterial oxygen tension can be pre-set.
In one series of experiments, the lower limit was set at 7.3kPa (55mm Hg) and the upper limit at 1 0.7kPa (80mm Hg).
The oxygen sensor was operated in accordance with the position of the flat, constant-current, portion of the characteristic curve, as shown in Figure 2.
Over a certain voltage range, the current remains constant irrespective of voltage variations, and was altered only in proportion to detected changes in oxygen concentration in the blood being analysed.
When the measured oxygen concentration fell outside the pre-set range, the sensor caused the shaft 14 to be rotated in the appropriate direction and by such an amount that the oxygen concentration was altered by 5% in the direction causing the arterial oxygen tension to move back towards the nearer limit.
The apparatus was intended to sample the oxygen concentration at intervals of one minute. If the reading taken one minute after an oxygen change indicated that the arterial oxygen tension was still outside limits, a further change of 5% and in the same direction was made. This process was repeated a third time, resulting in an overall change of 15% in the oxygen concentration supplied to the patient. As soon as the third successive change was made, and irrespective of its success in bringing the oxygen concentration back within limits, an alarm associated with control unit 12 was activated. This was in case manual intervention was necessary to prevent either hypoxia or hyperoxia.
The unit 12 also included means for providing a pre-set concentration of oxygen in the gas issuing from mixer 6 in the event of a mains failure. Means were also provided by which any desired inspired oxygen concentration could be produced by manually controlling the mixer.
With the above sampling rates and sizes of changes (5%) in the oxygen concentration, it has been found that the number of episodes during which the arterial oxygen tension was outside the above chosen limits was more on servo-control than on manual control, but the proportion of time spent
outside these limits was less with servo-control than
with manual control. Overall, the arterial oxygen
tension was outside the set limits for 15.2% of the
time when on servo-control, and for 31.1% of the
time when on manual control. From the above
information it will be appreciated that the optimum
sampling intervals, and the size of the change in the
inspired oxygen concentration have yet to be deter
mined. Ideally there should be fewer excursions out
side the set limits with servo-control than with man
ual control, as well as ensuring that the total time
spent outside these limits was significantly less with servo-control than with manual control.
Although the apparatus as used included an
umbilical arterial catheter-tip electrode, with a
matched oxygen meter, it is within the purview of the present invention to use a transcutaneous electrode with a similarly-matched oxygen meter to achieve the same desired effect. Any continuouslyreading sensor of arterial oxygen tension may be used in the equipment The oxygen-enriched air which is regulated by the control unit may be supplied to the patient directly into an incubator, headbox or face mask, or indirectly, as by means of a mechanical ventilator.
Claims (9)
1. An apparatus for controlling the oxygen concentration in a respirable mixture of air and oxygen issuing from a gas mixer for delivery to a a patient, comprising a device for generating a signal corresponding to the oxygen concentration in the blood of the patient connected to the device, a control unit adapted to receive the signal and to alter the oxygen concentration in the respirable gas issuing from the mixer in one or more discrete amounts when the signal exceeds a preselected limit.
2. An apparatus as claimed in Claim 1, in which the control unit is connected to the mixer and includes a shaft which enters the mixer, the angular position of which shaft controls the percentage of oxygen in the gas mixture issuing from the mixer.
3. An apparatus as claimed in Claim 2, in which the control unit includes a servo-motor connected to the shaft for rotating the shaft in preselected discrete angular steps.
4. An apparatus as claimed in Claim 3, in which each preselected angular step of the shaft results in a 5% change in oxygen concentration.
5. An apparatus as claimed in any one of Claims 1 to 4, in which the signal generating device is an intravascular electrode.
6. An apparatus as claimed in any one of Claims 1 to 4, in which the signal generating device is a heated skin-surface electrode.
7. An apparatus as claimed in any one of Claims 1 to 6, in which the control unit includes means for preselecting upper and lower limits of arterial oxygen tension in the patient.
8. An apparatus for controlling the oxygen concentration in a respirable mixture of air and oxygen,
including a device for generating a signal corres
ponding to the oxygen concentration in the blood of
a patient connected to the device; a control unit con
nected to the mixer of air and oxygen and adapted to
alter the oxygen concentration, in the gas issuing when the said signal goes outside the chosen maximum and minimum limits corresponding to maximum and minimum limits of arterial oxygen tension, and means for supplying the respirable mixture to the patient.
9. An apparatus for controlling the oxygen concentration in a respirable mixture of air and oxygen issuing from a gas mixer for delivery to a patient, constructed, arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated in the Figures of the accompanying drawing.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB7938944A GB2036565A (en) | 1978-11-13 | 1979-11-09 | Oxygen concentration control |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB7844269 | 1978-11-13 | ||
GB7938944A GB2036565A (en) | 1978-11-13 | 1979-11-09 | Oxygen concentration control |
Publications (1)
Publication Number | Publication Date |
---|---|
GB2036565A true GB2036565A (en) | 1980-07-02 |
Family
ID=26269557
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB7938944A Withdrawn GB2036565A (en) | 1978-11-13 | 1979-11-09 | Oxygen concentration control |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB2036565A (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1986002565A1 (en) * | 1984-11-01 | 1986-05-09 | Bear Medical Systems, Inc. | Electronically-controlled gas blending system |
GB2228684A (en) * | 1989-01-24 | 1990-09-05 | Draegerwerk Ag | Recirculatory respiratory protective apparatus |
-
1979
- 1979-11-09 GB GB7938944A patent/GB2036565A/en not_active Withdrawn
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1986002565A1 (en) * | 1984-11-01 | 1986-05-09 | Bear Medical Systems, Inc. | Electronically-controlled gas blending system |
US4602653A (en) * | 1984-11-01 | 1986-07-29 | Bear Medical Systems, Inc. | Electronically-controlled gas blending system |
GB2228684A (en) * | 1989-01-24 | 1990-09-05 | Draegerwerk Ag | Recirculatory respiratory protective apparatus |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |