CA1107616A - Blood gases sampling probe - Google Patents
Blood gases sampling probeInfo
- Publication number
- CA1107616A CA1107616A CA295,024A CA295024A CA1107616A CA 1107616 A CA1107616 A CA 1107616A CA 295024 A CA295024 A CA 295024A CA 1107616 A CA1107616 A CA 1107616A
- Authority
- CA
- Canada
- Prior art keywords
- opening
- chamber
- gases
- blood
- openings
- 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.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
- G01N33/483—Physical analysis of biological material
- G01N33/487—Physical analysis of biological material of liquid biological material
- G01N33/49—Blood
- G01N33/4925—Blood measuring blood gas content, e.g. O2, CO2, HCO3
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- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Biomedical Technology (AREA)
- Chemical & Material Sciences (AREA)
- Hematology (AREA)
- Physics & Mathematics (AREA)
- Food Science & Technology (AREA)
- Molecular Biology (AREA)
- Urology & Nephrology (AREA)
- Ecology (AREA)
- Biophysics (AREA)
- Medicinal Chemistry (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analysing Biological Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A device and method are provided for separating gases from a stream of blood passing through the device.
The device comprises a gas impervious chamber having at least three openings, a porous body contained in the chamber and defining a passage extending between a first and second of said three openings, and a gas permeable membrane lining the passage. The membrane is supported against deformation by the porous body and extends between the first and second openings. A third of the three openings is positioned to withdraw gases from the porous body whereby upon flowing the stream of blood through the device by way of the first opening, the passage and the second opening, gases from the blood will permeate the membrane so that by applying a vacuum to the third opening these gases can be drawn through the porous body and out of the chamber for analysis.
A device and method are provided for separating gases from a stream of blood passing through the device.
The device comprises a gas impervious chamber having at least three openings, a porous body contained in the chamber and defining a passage extending between a first and second of said three openings, and a gas permeable membrane lining the passage. The membrane is supported against deformation by the porous body and extends between the first and second openings. A third of the three openings is positioned to withdraw gases from the porous body whereby upon flowing the stream of blood through the device by way of the first opening, the passage and the second opening, gases from the blood will permeate the membrane so that by applying a vacuum to the third opening these gases can be drawn through the porous body and out of the chamber for analysis.
Description
This invention relates to a device and to a method for sampling gases from a subject's arterial blood to permit analysis of these gases.
The present invention has a particular usefulness in studying gases in the bloodstream of divers.
; A subject exposed to super-atmospheric pressure accumulates gases in muscle tissue, fat, and after a longer period in bone. The partial pressure of various gases in the blood-stream is an essential part of the information needed to determine the time constant for blood, fat, muscle and bone which in effect dictate how long the subject should be given to return to atmospheric pressure. Because of the extreme danger inherent in returning to atmospheric pressure too quickly, divers are presently brought bac~ to atmospheric p~essure over relatively long periods which could be reduced if accurate time constants were available.
One attempt which has been made to sample gases from blood includes the use of a stainless steel catheter having several very small openings at its end and covered by a gas permeable material such as TEFLON (registered trade mark) or SIL~STIC (registered trade mark). The intent is to permit permeation of the various gases present in the bloodstream through the mernbrane and through the small openings in -the catheter. The gases can then be drawn off and fed to a mass spectrometer. ~ere the partial pressures of the various gases are displayed on the face of the mass spectrometer for direct reading.
Probes of this type can be calibrated only with difficulty. The calibration must be done under strict conditions using tonometered solutions containing standard
The present invention has a particular usefulness in studying gases in the bloodstream of divers.
; A subject exposed to super-atmospheric pressure accumulates gases in muscle tissue, fat, and after a longer period in bone. The partial pressure of various gases in the blood-stream is an essential part of the information needed to determine the time constant for blood, fat, muscle and bone which in effect dictate how long the subject should be given to return to atmospheric pressure. Because of the extreme danger inherent in returning to atmospheric pressure too quickly, divers are presently brought bac~ to atmospheric p~essure over relatively long periods which could be reduced if accurate time constants were available.
One attempt which has been made to sample gases from blood includes the use of a stainless steel catheter having several very small openings at its end and covered by a gas permeable material such as TEFLON (registered trade mark) or SIL~STIC (registered trade mark). The intent is to permit permeation of the various gases present in the bloodstream through the mernbrane and through the small openings in -the catheter. The gases can then be drawn off and fed to a mass spectrometer. ~ere the partial pressures of the various gases are displayed on the face of the mass spectrometer for direct reading.
Probes of this type can be calibrated only with difficulty. The calibration must be done under strict conditions using tonometered solutions containing standard
- 2 -s gases at known pressures and at fixed temperatures.
However, even with the most strict calibration of this type once the probe has been introduced into a blood vessel it can no longer be calibrated so that it is impossible to check that the calibration of the probe achieved using the tonometered solution is maintained after entry into - an artery. Further, it has been found that when such a probe is subjected to temperature changes its calibration has been influenced and even disrupted.
Another important consideration is the position of the probe inside the blood vessel. It will be evident that it is possible to place the probe in such a position that at least some of the openings are occluded by engagement with a wall of an artery. Theoretically the probe should lie in the centre of the bloodstream through the artery for optimum sampling of the gases. Unfortunately it is not possible to ensure that the probe sits in this position and consequently its use can never be accurate.
A further disadvantage of existing probes is the problem of creating a membrane which is sufficiently thin to permit gas permeation quite quickly while at the same time covering the openings in the catheter without being drawn into the openings. In practice it has been found that devices of this type tend to suffer from a long response time and consequently sudden short changes or fluctuations in partial pressure are not evident at the mass spectrometer.
Although the above problems with existing probes are evident at atmospheric pressure, the difficulties are enhanced even more when the sub,ect is exposed to ~76~
super-atmospheric pressures. In such a situation tne probe can be calibrated only at normal atmospheric pressure before increasing the pressure and it appears that such increase in pressure induces important changes in the probe characteristics and that nothing can be done to ad~ust for these changes. Because of such drawbacks, the r~sults obtained with such probes are unreliable, inaccurate and not reproducible. Consequently the results are of little use in determining time constants suitable for use in creating a program for de-pressurizing divers.
The present invention is intended to provide a device and method for use in determining partial pressures of gases present in a bloodstream, and more particularly to entrain such gases in such a way that they can be fed to a mass spectrometer which will give a direct reading of their partial pressures.
According to one aspect of the invention a device is provided for separating gases from a stream of blood passing through the device. The device comprises a gas impervious chamber having at least three openin~s, a porous body contained in the chamber and defining a passage extending between a first and second of said three openings, and a gas permeabl~ membrane lining the passage.
The membrane is supported against deformation by the porous body and extends between the first and second openings. A third of the three openings is positioned to withdraw gases from the porous body whereby upon flowing the stream of blood through the device by way of the first opening, the passage and the second opening, gases from the blood will permeate the membrane so that by applying a /
76~
vacuum to the third opening these gases can be drawn through the porous body and out of the chamber for analysis.
In another of its aspects the invention provides a method of sampling gases from the blood of a subject. The method comprises the steps of making connections to an artery to remove from and to return blood to the artery, passing blood from the artery through a passage lined by a gas permeable layer supported by a porous body, applying a negative pressure about the porous body to entrain gases which having left the blood permeate the permeable layer and pass through the porous body, and passing the entrained gases to a mass spectrometer to analyse the gases so sampled.
These and other aspects of the invention will be more readily understood with reference to the drawings, in which;
Fig. 1 is a somewhat diagramatic perspective view of a first embodiment of the invention with portions broken away to illustrate internal parts of the device; and Fig. 2 is a perspective view of a preferred embodiment of the invention incorporating most of the structure shown in Fig. 1.
Reference is first made to Fig. 1 to describé a first embodiment of the invention. As seen in Fig. 1 a device denoted generally by the numeral 20 is adapted to receive blood through an inlet tube 22 which is ~e ~brc~
lined by a gas permeable diaphL-~ 24 of TEFLON or SILASTIC.
~ ~ ~ b~
This ~k~h~gm continues through a central opening in an annular porous body 26 of sintered metal and terminates in ~ 30 an outlet 2~ where blood leaves the device.
:
~7~$
The porous body 26 is contained in a cylindrical stainless steel chamber 30 defining three openings. A first of these openings 32 is defined in an end wall 34, a corresponding opening at the opposite end of the chamber (not seen) is the second opening, and a third opening 36 is defined in a said wall 38 of the chamber 30. The third opening is associated with a stainless steel pipe 40 which can be connected to a vacuum source to withdraw gases which leave the blood and J~ ~ ~, ~) ~`Q ~1 ~
Blo permeate the diaphr~m 24. The porous body 26 defines random paths each of which has an opening size of about 1 micrometer so that the gases will pass readily through the porous body and be withdrawn through the tube 40.
End wall 34 of the chamber 30 has a tubular extension 42 forming part of the inlet 22 and a corresponding extension is provided at the opposite end of the device.
The chamber 30, tubular extension 42, corresponding extension at the opposite end, and a portion of the gas removal tube 40 are encapsulated in a protective coating 44 of TEFLON, SILASTIC or an equivalent material.
In use the subject whose blood is to be analysed first has an artery severed so that a catheter system can be inserted for removing blood and for returning the blood to the artery. The device is calibrated by feeding a known solution having certain gas constituents to the inlet 22 and by connecting the tube 40 to a mass spectrometer so that the readings of partial pressure can be set to correspond to those known in the test solutlon.
After calibration -the supply of blood from the subject is connected to the inlet 22 and the return is connected to ~.~L'n'76~
the outlet 28. The mass spectrometer is connected to the tube 40 and the gas is analysed continuously showing readings of partial pressure on the mass spectrometer.
Because of the suhstantial support given to membrane 24 by the porous body 26 it is possible to subject the mem~rane to super-atmospheric pressure without noticeable effect on the results. Further, this adequate support results in a mem~rane of limited thickness so that the response time for changes in partial pressure is quite short and the mass spectrometer will react quite quickly to rapid changes in partial pressure.
In a typical embodiment the overall length of the chamber 30 is 2 millimeters, the internal diameter is 10 millimeters, the membrane 24 has an internal diameter of 4 millimeters and the internal diameter of the tube leading to the mass spectrometer has a diameter of 1 milliméter.
Although the first embodiment already described will be preferred in some circumstances, the embodiment shown in Fig. 2 will be preferred where it is desired to calibrate the device intermittently during testing without disconnecting the device from the subject.
.As seen in Fig. 2 a device 20' has a gas outlet tube 40', an inlet 22' and an outlet 28'. A Y-connection 46 is provided at the inlet 22' and a similar connection 48 is provided at the outlet 28~. ~s a result one branch of each of the Y-connections can be used to feed blood into and from the device and the other brances can be used to feed standard solutions having known partial pressures.
However, even with the most strict calibration of this type once the probe has been introduced into a blood vessel it can no longer be calibrated so that it is impossible to check that the calibration of the probe achieved using the tonometered solution is maintained after entry into - an artery. Further, it has been found that when such a probe is subjected to temperature changes its calibration has been influenced and even disrupted.
Another important consideration is the position of the probe inside the blood vessel. It will be evident that it is possible to place the probe in such a position that at least some of the openings are occluded by engagement with a wall of an artery. Theoretically the probe should lie in the centre of the bloodstream through the artery for optimum sampling of the gases. Unfortunately it is not possible to ensure that the probe sits in this position and consequently its use can never be accurate.
A further disadvantage of existing probes is the problem of creating a membrane which is sufficiently thin to permit gas permeation quite quickly while at the same time covering the openings in the catheter without being drawn into the openings. In practice it has been found that devices of this type tend to suffer from a long response time and consequently sudden short changes or fluctuations in partial pressure are not evident at the mass spectrometer.
Although the above problems with existing probes are evident at atmospheric pressure, the difficulties are enhanced even more when the sub,ect is exposed to ~76~
super-atmospheric pressures. In such a situation tne probe can be calibrated only at normal atmospheric pressure before increasing the pressure and it appears that such increase in pressure induces important changes in the probe characteristics and that nothing can be done to ad~ust for these changes. Because of such drawbacks, the r~sults obtained with such probes are unreliable, inaccurate and not reproducible. Consequently the results are of little use in determining time constants suitable for use in creating a program for de-pressurizing divers.
The present invention is intended to provide a device and method for use in determining partial pressures of gases present in a bloodstream, and more particularly to entrain such gases in such a way that they can be fed to a mass spectrometer which will give a direct reading of their partial pressures.
According to one aspect of the invention a device is provided for separating gases from a stream of blood passing through the device. The device comprises a gas impervious chamber having at least three openin~s, a porous body contained in the chamber and defining a passage extending between a first and second of said three openings, and a gas permeabl~ membrane lining the passage.
The membrane is supported against deformation by the porous body and extends between the first and second openings. A third of the three openings is positioned to withdraw gases from the porous body whereby upon flowing the stream of blood through the device by way of the first opening, the passage and the second opening, gases from the blood will permeate the membrane so that by applying a /
76~
vacuum to the third opening these gases can be drawn through the porous body and out of the chamber for analysis.
In another of its aspects the invention provides a method of sampling gases from the blood of a subject. The method comprises the steps of making connections to an artery to remove from and to return blood to the artery, passing blood from the artery through a passage lined by a gas permeable layer supported by a porous body, applying a negative pressure about the porous body to entrain gases which having left the blood permeate the permeable layer and pass through the porous body, and passing the entrained gases to a mass spectrometer to analyse the gases so sampled.
These and other aspects of the invention will be more readily understood with reference to the drawings, in which;
Fig. 1 is a somewhat diagramatic perspective view of a first embodiment of the invention with portions broken away to illustrate internal parts of the device; and Fig. 2 is a perspective view of a preferred embodiment of the invention incorporating most of the structure shown in Fig. 1.
Reference is first made to Fig. 1 to describé a first embodiment of the invention. As seen in Fig. 1 a device denoted generally by the numeral 20 is adapted to receive blood through an inlet tube 22 which is ~e ~brc~
lined by a gas permeable diaphL-~ 24 of TEFLON or SILASTIC.
~ ~ ~ b~
This ~k~h~gm continues through a central opening in an annular porous body 26 of sintered metal and terminates in ~ 30 an outlet 2~ where blood leaves the device.
:
~7~$
The porous body 26 is contained in a cylindrical stainless steel chamber 30 defining three openings. A first of these openings 32 is defined in an end wall 34, a corresponding opening at the opposite end of the chamber (not seen) is the second opening, and a third opening 36 is defined in a said wall 38 of the chamber 30. The third opening is associated with a stainless steel pipe 40 which can be connected to a vacuum source to withdraw gases which leave the blood and J~ ~ ~, ~) ~`Q ~1 ~
Blo permeate the diaphr~m 24. The porous body 26 defines random paths each of which has an opening size of about 1 micrometer so that the gases will pass readily through the porous body and be withdrawn through the tube 40.
End wall 34 of the chamber 30 has a tubular extension 42 forming part of the inlet 22 and a corresponding extension is provided at the opposite end of the device.
The chamber 30, tubular extension 42, corresponding extension at the opposite end, and a portion of the gas removal tube 40 are encapsulated in a protective coating 44 of TEFLON, SILASTIC or an equivalent material.
In use the subject whose blood is to be analysed first has an artery severed so that a catheter system can be inserted for removing blood and for returning the blood to the artery. The device is calibrated by feeding a known solution having certain gas constituents to the inlet 22 and by connecting the tube 40 to a mass spectrometer so that the readings of partial pressure can be set to correspond to those known in the test solutlon.
After calibration -the supply of blood from the subject is connected to the inlet 22 and the return is connected to ~.~L'n'76~
the outlet 28. The mass spectrometer is connected to the tube 40 and the gas is analysed continuously showing readings of partial pressure on the mass spectrometer.
Because of the suhstantial support given to membrane 24 by the porous body 26 it is possible to subject the mem~rane to super-atmospheric pressure without noticeable effect on the results. Further, this adequate support results in a mem~rane of limited thickness so that the response time for changes in partial pressure is quite short and the mass spectrometer will react quite quickly to rapid changes in partial pressure.
In a typical embodiment the overall length of the chamber 30 is 2 millimeters, the internal diameter is 10 millimeters, the membrane 24 has an internal diameter of 4 millimeters and the internal diameter of the tube leading to the mass spectrometer has a diameter of 1 milliméter.
Although the first embodiment already described will be preferred in some circumstances, the embodiment shown in Fig. 2 will be preferred where it is desired to calibrate the device intermittently during testing without disconnecting the device from the subject.
.As seen in Fig. 2 a device 20' has a gas outlet tube 40', an inlet 22' and an outlet 28'. A Y-connection 46 is provided at the inlet 22' and a similar connection 48 is provided at the outlet 28~. ~s a result one branch of each of the Y-connections can be used to feed blood into and from the device and the other brances can be used to feed standard solutions having known partial pressures.
3~ Consequently with suitable and conventional valving it ~' - 7 -~7~
is possible to feed either blood or standard solution through the device so that calibration can take place at any time. The solution would of course be compatible with blood so that traces oE the solution entering the bloodstream would be inconsequential.
It will now be evident that the device permits gas analysis of partial pressures in the blood-stream of a subject over a wide range of pressures with-out the inherent difficulties created when using catheters having membranes stretched over the end to control g~s permeation. The device according to the invention provides accurate analysis and has a quick response time so that rapid changes in partial pressures will appear as readings on a mass spectrometer.
It will also be evident that a device can take many forms. Although it is convenient to provide a device having a general cylindrical shape it is of course possible to vary this shape within the concept of the invention. Any such changes in shape shouId be within the principle of providing adequate support for the membrane 24 and for providing structure to enable gases which permeate the membrane to be withdrawn from the structure for feeding to a mass spectrometer. Wi-thin these general requirements many changes in structure are possible in accordance with the invention.
is possible to feed either blood or standard solution through the device so that calibration can take place at any time. The solution would of course be compatible with blood so that traces oE the solution entering the bloodstream would be inconsequential.
It will now be evident that the device permits gas analysis of partial pressures in the blood-stream of a subject over a wide range of pressures with-out the inherent difficulties created when using catheters having membranes stretched over the end to control g~s permeation. The device according to the invention provides accurate analysis and has a quick response time so that rapid changes in partial pressures will appear as readings on a mass spectrometer.
It will also be evident that a device can take many forms. Although it is convenient to provide a device having a general cylindrical shape it is of course possible to vary this shape within the concept of the invention. Any such changes in shape shouId be within the principle of providing adequate support for the membrane 24 and for providing structure to enable gases which permeate the membrane to be withdrawn from the structure for feeding to a mass spectrometer. Wi-thin these general requirements many changes in structure are possible in accordance with the invention.
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A device for separating gases from a stream of liquid passing through the device, the liquid being selected from blood and a calibrating solution, the device comprising:
a gas impervious chamber having at least three openings;
a porous body contained in the chamber, and defining a passage extend-ing between a first and second of said at least three openings;
a gas permeable membrane lining the passage and supported against deformation by the body, the membrane extending between said first and second openings, a third of the at least three openings being connected to said gas impervious chamber and positioned to withdraw gases from the porous body when a vacuum is applied to the third opening whereby upon flowing said stream of liquid through the device by way of the first opening, the passage and the second opening, gases from the liquid will permeate the membrane so that upon application of said vacuum to the third opening these gases can be drawn through the porous body and out of the chamber for analysis.
a gas impervious chamber having at least three openings;
a porous body contained in the chamber, and defining a passage extend-ing between a first and second of said at least three openings;
a gas permeable membrane lining the passage and supported against deformation by the body, the membrane extending between said first and second openings, a third of the at least three openings being connected to said gas impervious chamber and positioned to withdraw gases from the porous body when a vacuum is applied to the third opening whereby upon flowing said stream of liquid through the device by way of the first opening, the passage and the second opening, gases from the liquid will permeate the membrane so that upon application of said vacuum to the third opening these gases can be drawn through the porous body and out of the chamber for analysis.
2. A device as claimed in claim 1 in which the porous body defines random paths for the gases and these paths have cross-sectional widths of about one micrometer.
3. A device as claimed in claim 1 in which the gas impervious chamber is cylindrical and in which the porous body is cylindrical, the chamber inclu-ding end walls and a side wall, the end walls defining the first and second openings and the side wall defining the third opening.
4. A device as claimed in claim 1 in which the gas permeable membrane is selected from TEFLON and SILASTIC.
5. A device as claimed in claim 1 and further comprising means coupled to the chamber and adapted to carry said flow of blood to the first opening and from the second opening, said means including structure adapted to connect the device to respective input and output catheters.
6. A device as claimed in claim 1 and further comprising first means coupled to the chamber for carrying a flow of blood to the first opening and from the second opening, and second means for carrying a calibrating solution to the first opening and from the second opening, said first and second means connecting the device to respective input and output catheters so that calibra-ting solution can be fed through the device to the exclusion of blood flow and vice versa.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA295,024A CA1107616A (en) | 1978-01-16 | 1978-01-16 | Blood gases sampling probe |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA295,024A CA1107616A (en) | 1978-01-16 | 1978-01-16 | Blood gases sampling probe |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1107616A true CA1107616A (en) | 1981-08-25 |
Family
ID=4110553
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA295,024A Expired CA1107616A (en) | 1978-01-16 | 1978-01-16 | Blood gases sampling probe |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1107616A (en) |
-
1978
- 1978-01-16 CA CA295,024A patent/CA1107616A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |