WO2012077065A1 - Procédé et appareil pour déterminer la pression partielle de dioxyde de carbone dans le sang artériel - Google Patents

Procédé et appareil pour déterminer la pression partielle de dioxyde de carbone dans le sang artériel Download PDF

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Publication number
WO2012077065A1
WO2012077065A1 PCT/IB2011/055510 IB2011055510W WO2012077065A1 WO 2012077065 A1 WO2012077065 A1 WO 2012077065A1 IB 2011055510 W IB2011055510 W IB 2011055510W WO 2012077065 A1 WO2012077065 A1 WO 2012077065A1
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subject
gas
arterial blood
carbon dioxide
modulation
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PCT/IB2011/055510
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English (en)
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Josephus Arnoldus Henricus Maria Kahlman
Jeroen Veen
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Koninklijke Philips Electronics N.V.
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Publication of WO2012077065A1 publication Critical patent/WO2012077065A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
    • A61B5/083—Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption
    • A61B5/0836—Measuring rate of CO2 production
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
    • A61B5/0205—Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
    • A61B5/02055—Simultaneously evaluating both cardiovascular condition and temperature
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
    • A61B5/082—Evaluation by breath analysis, e.g. determination of the chemical composition of exhaled breath
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/14542—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue for measuring blood gases
    • 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
    • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/10—Preparation of respiratory gases or vapours
    • A61M16/1005—Preparation of respiratory gases or vapours with O2 features or with parameter measurement
    • A61M16/101—Preparation of respiratory gases or vapours with O2 features or with parameter measurement using an oxygen concentrator
    • 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
    • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/10—Preparation of respiratory gases or vapours
    • A61M16/12—Preparation of respiratory gases or vapours by mixing different gases
    • 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
    • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/20—Valves specially adapted to medical respiratory devices
    • A61M16/201—Controlled valves
    • A61M16/202—Controlled valves electrically actuated
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B10/00—Other methods or instruments for diagnosis, e.g. instruments for taking a cell sample, for biopsy, for vaccination diagnosis; Sex determination; Ovulation-period determination; Throat striking implements
    • A61B2010/0083—Other methods or instruments for diagnosis, e.g. instruments for taking a cell sample, for biopsy, for vaccination diagnosis; Sex determination; Ovulation-period determination; Throat striking implements for taking gas samples
    • A61B2010/0087—Breath samples
    • 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
    • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/0045—Means for re-breathing exhaled gases, e.g. for hyperventilation treatment
    • 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
    • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/10—Preparation of respiratory gases or vapours
    • A61M16/1005—Preparation of respiratory gases or vapours with O2 features or with parameter measurement
    • A61M2016/102—Measuring a parameter of the content of the delivered gas
    • A61M2016/1025—Measuring a parameter of the content of the delivered gas the O2 concentration
    • 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
    • A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
    • A61M16/10—Preparation of respiratory gases or vapours
    • A61M16/1005—Preparation of respiratory gases or vapours with O2 features or with parameter measurement
    • A61M2016/102—Measuring a parameter of the content of the delivered gas
    • A61M2016/103—Measuring a parameter of the content of the delivered gas the CO2 concentration
    • 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
    • A61M2230/005—Parameter used as control input for the apparatus
    • 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)
    • 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
    • A61M2230/208—Blood composition characteristics pH-value
    • 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
    • A61M2230/40—Respiratory characteristics
    • A61M2230/42—Rate

Definitions

  • the present invention relates to a method and apparatus for measuring partial carbon dioxide pressure.
  • it relates to a method, apparatus and system for measuring, non-invasively, partial carbon dioxide pressure in arterial blood of a subject.
  • NIV Non Invasive Ventilation
  • COPD Chronic Obstructive Pulmonary Disease
  • a patient wears a cushioned mask which is connected to an air pump machine.
  • the air may be supplied from environmental air or supplemental oxygen in which the concentration of oxygen can be increased and the concentration of nitrogen reduced.
  • a slightly pressurized airflow is blown into the mask while the patient breathes; the strength of the pressure may be varied during the breathing cycle. For example, the airflow may be strongest when the patient breathes in, to help the patient take in as much air as possible.
  • Airflow pressure is lowered when the patient breathes out, but remains positive. This continual positive pressure helps to 'splint' the airways open, enabling more air to get in and out of the lungs.
  • the aim of using NIV is to increase oxygen levels and particularly to help the patient breathe out more carbon dioxide.
  • the efficacy and adjustment of the ventilator is checked by measuring the base-line and the overnight trends in the arterial oxygen and carbon dioxide levels of the patient. This is, invariably, achieved by measuring blood gas partial pressures.
  • ICU Intensive Care Unit
  • the blood gas partial pressures that are measured are the partial oxygen pressure and/or partial carbon dioxide pressure.
  • a known technique for monitoring the partial arterial oxygen pressure (Pa02) of the patient's blood is to measure the arterial oxygen saturation (Sa02) and then using the Oxygen Dissociation Curve (ODC) derive the partial arterial oxygen pressure (Pa02) from the measured arterial oxygen saturation (Sa02).
  • ODC Oxygen Dissociation Curve
  • Sa02 equals the percentage of hemoglobin binding sites in the arterial bloodstream occupied by oxygen.
  • the arterial oxygen saturation can be measured, using a variety of known techniques. Pulse oximetry is an optical method for non-invasive monitoring of arterial oxygen saturation of a patient and has become one of the most commonly used techniques in clinical practice.
  • the protein hemoglobin (Hb) binds oxygen in the red blood cells for transport through the body, and has the property of changing from dark red to bright red in color when oxygenated.
  • pulse oximeters determine the light absorbance in a peripheral vascular bed to arrive at an indirect estimate of oxygen saturation (Sp02, i.e. Sa02 as measured using a pulse oximeter). Pulse oximeters rely on the changes in arterial blood volume caused by cardiac contraction and relaxation to determine the amount of light absorbed by pulsating arterial blood alone, thereby largely factoring out the contributions of tissue and venous blood.
  • transcutaneous C0 2 monitoring Another known technique for monitoring PaC02 is transcutaneous C0 2 monitoring. This involves placement of an electrode on the patient's skin. The skin tissue is heated to increase its permeability and the C0 2 pressure of the tissue is measured. The C0 2 pressure of the tissue may vary from the actual arterial C0 2 pressure making this form of measurement also prone to inaccuracies. The elevated temperature required for operation of the transcutaneous electrodes increases the levels of C0 2 . The resulting measurements then have to be temperature corrected which can also introduce inaccuracies. Further, the heating of the electrodes make them uncomfortable for the patient to wear, often requiring repositioning. Further, the electrodes are prone to damage.
  • transcutaneous C0 2 pressure is affected by skin thickness and capillary density which results in large variations in readings and therefore positioning of the electrodes is critical. This makes the use of transcutaneous C0 2 monitoring difficult for use at home by a patient as location of placement of the electrodes is critical and the requirement for frequent recalibration.
  • Another known technique is use of deriving the partial C0 2 pressure in the blood from the ODC as disclosed, for example, in EP 0944347, in which the saturated oxygen levels are measured using an oximeter at two different, known temperatures. This requires the oximeter to include a heating/cooling element which may prove uncomfortable for the patient for long term monitoring.
  • the present invention seeks to provide determination of arterial partial carbon dioxide pressure (PaC02) with increased accuracy whilst mitigating the above, additional disadvantages.
  • PaC02 arterial partial carbon dioxide pressure
  • a method for determining a partial carbon dioxide pressure in arterial blood of a subject comprising the steps of: modulating at least one parameter of arterial blood of a subject; deriving oxygen saturation of the arterial blood of the subject during modulation of the said at least one parameter; and determining partial carbon dioxide pressure of the subject from said derived oxygen saturation.
  • a system for determining a partial carbon dioxide pressure in arterial blood of a subject comprising: a modulator for modulating at least one parameter of arterial blood of a subject; a sensory system for deriving oxygen saturation of the arterial blood of the subject during modulation of said at least one parameter of said subject; and a processor for determining partial carbon dioxide pressure from the derived oxygen saturation.
  • PaC02 pressure with increased accuracy is determined which avoids the use of additional sensors for indirect PaC02 measurement (capnography, transcutaneous), and thereby removes all the problems associated with these sensors.
  • the apparatus can be easily integrated into existing ventilator systems, in particular, NIV systems which already include oxygen saturation monitoring.
  • the present invention can be applied in closed environments, like incubators for newborn or space applications where the gas composition of the whole volume is modulated. This avoids the use of transcutaneous sensors, which is the current practice. The modulation of the parameters only requires small changes to be modulated which are not noticeable by the patient, thus increasing the patient's comfort.
  • modulation of a parameter is considered to be varying the parameter cyclically over more than two cycles, preferably, over a continuous time period of several modulation cycles.
  • the modulation of the at least one parameter may be gradual (e.g. sinusoidal), or step-wise (e.g. square wave).
  • the concentrations of said at least two gas components may be modulated by modulating the inspired oxygen fraction of the supplied gas and/or by modulating the inspired carbon dioxide fraction of the supplied gas.
  • This may be slow (over several breathing cycles) modulation of the inhaled gas composition induces variations in Sp0 2 and/or the respiratory minute volume (MV), which are indicative for the actual blood pH and thus the actual PaC02 This is because as inspired carbon dioxide fraction (FiC0 2 ) increases, the body will increase MV too in order to expel the excess of C0 2 .
  • MV respiratory minute volume
  • the at least one parameter of in arterial blood of a subject being modulated may be the blood temperature of the subject.
  • the temperature is modulated, only a small temperature change is required to enable the PaC02 to be determined. This minimizes discomfort to the patient.
  • this can be easily brought about by controlling the use of the emitter (LED) of exiting oximeters and thus the heating effect of the LED. This may be achieved by varying the duty cycle of the driving currents of the LED. Therefore, the apparatus of the invention may be easily integrated into existing ventilator systems.
  • LED emitter
  • the oxygen saturation of the arterial blood of said subject may be derived by measuring the oxygen saturation of the arterial blood of the subject using simple and robust probes such as a pulse oximeter, and/or it may be derived from monitoring the (MV) by measuring the respiration rate and/or depth of the subject.
  • This measuring and/or monitoring may be synchronized with the modulation cycle of the supplied gas concentrations. Therefore, the modulation of the partial pressures may be small (+/- 1 kPa), such that no additional discomfort to the patient is caused. For this reason also the signal is small, but averaging overnight using many modulation cycles enhances the signal to noise ratio (SNR).
  • SNR signal to noise ratio
  • An additional advantage of this measuring scheme is that variations in the actual Sp0 2 value due to physiological processes do not impair the modulation measurement, since they are essentially decoupled.
  • the inspired gas fractions of the supplied are modulated at a rate such that the Pa02 is also modulated.
  • Oxygen saturation readings may be taken at different Pa02 2 levels and using the ODC, the pH can be determined and from said the pH, the partial carbon dioxide pressure can be determined. This has proved to provide a measure of the partial carbon dioxide pressure at 0.2kPa accuracy.
  • pH « pKa - jSPaC0 2 wherein pH is the pH value of the arterial blood of said subject, pKa is a ionization constant of the arterial blood of the subject, pKa being preferably within the range of 7.5 to 8, ⁇ is a personal coefficient of the subject, ⁇ being preferably within the range of 0.04 to 0.08 and PaC0 2 is the arterial partial carbon dioxide pressure.
  • pKa is about 7.7 and ⁇ is about 0.06.
  • Fig. 1 is an example of an Oxygen Dissociation Curve (ODC) for different pH values of arterial blood of a subject as a function of partial oxygen pressure p02;
  • ODC Oxygen Dissociation Curve
  • Fig. 2 is an example of a local slope of the ODC of Fig. 1;
  • Fig. 4 is an example of the saturated oxygen signal oxygen modulation for 0.2kPa partial carbon dioxide pressure deviation
  • Fig. 5 is an example of an ODC for different pH values of arterial blood of a subject as a function of temperature
  • Fig. 6 is an example of a local slope of the ODC of Fig. 5;
  • Fig. 8 is an example of the saturated oxygen signal oxygen modulation for 0.2kPa partial carbon dioxide pressure deviation, 2°C temperature modulation and p02 of 8kPA;
  • Fig. 9 is a simplified schematic of the system according to an embodiment of the present invention.
  • Fig. 10 is a simplified schematic of the apparatus for determining carbon dioxide pressure of the system of Fig. 9;
  • Fig. 11 is a simplified schematic of the apparatus for determining carbon dioxide pressure of the system of Fig. 9 according to another embodiment of the present invention.
  • the partial C0 2 pressure in arterial blood of a subject is determined by deriving oxygen saturation of the arterial blood of the subject at intervals as the concentration of the gas components supplied to the patient via a non-invasive ventilator, for example, are modulated. This may be achieved by synchronizing the derivation of the oxygen saturation with the modulation cycle of the supplied gas concentrations.
  • the partial carbon dioxide pressure is then determined from the derived oxygen saturation. This may be achieved by deriving the pH of the arterial blood of the patient from the changes in the oxygen saturation of the arterial blood due to the modulation of the gas concentrations and using the Oxygen
  • ODC Dissociation Curve
  • Pulmonary Disease generally range between 88-92% (7.3 ⁇ Pa0 2 ⁇ 8.5 kPa) since, due to their condition, they are unable to expel carbon dioxide from their lungs and the carbon dioxide is retained. Furthermore, low oxygen saturation in the range of 87-89% may be caused by sleep apnea which constricts the airway and reduces the amount of oxygen the lungs absorb. If the arterial partial oxygen pressure of a patient is varied, for example by varying the inspired oxygen fraction of the oxygen breathed in by the patient, this relation can be represented in a local slope of the ODC, which is shown in Figure 2.
  • pH « pKa - jSPaC0 2 wherein pKa is a ionization constant of the arterial blood of the subject and is ranging from 7.5 to 8 and ⁇ is a subject dependent coefficient and is ranging from 0.04 to 0.08.
  • pKa is about 7.7 and ⁇ is about 0.06 resulting in: pH « 7.7 - 0.06PaCO 2 [kPa], hence the required 0.2 kPa arterial partial carbon dioxide pressure accuracy compares to
  • a modulation of the variable indicated on the x axis causes a corresponding modulation of the variable indicated on the y axis wherein the modulation of the variable indicated on the y axis is dependent on the local slope of the curve.
  • the modulation of a parameter indicated on the y-axis can be determined.
  • a corresponding modulation of the variable indicated on the x axis can be derived using the slope of the curve.
  • a patient having non-invasive ventilation treatment is fitted with a cushioned mask 930 over their nose and mouth.
  • the mask is fed a pressurized gas for the patient to breathe.
  • the gas comprises at least two gas components, for example, oxygen and nitrogen. These may be provided by a first gas reservoir 950 and a second gas reservoir 970.
  • the first and second gas reservoirs 950, 970 may comprise pressurized tanks of the respective gases. These are mixed by a valve 940 and fed to the mask via a gas analyzer 920.
  • the embodiment illustrated gas components being provide by two separate gas reservoirs, it can be appreciated that the gases may be mixed and provided via a single reservoir such as a pressurized tank.
  • the first and second gas reservoirs may be replaced by a compressor which pressurizes the surrounding air to be delivered to the patient.
  • This may include an oxygen concentrator to increase the concentration of the oxygen of the air to be delivered to the patient. It may also include a carbon dioxide scrubber for removing carbon dioxide from the breath exhaled from the patient to recycle the air.
  • a gas source may be envisaged by persons skilled in the art.
  • the output of the gas analyzer 920 is connected to the apparatus 900 (shown in more detail in Figure 10).
  • the output of the apparatus is connected to the valve 940.
  • the output of a sensor 910 e.g.: a pulse oximeter
  • a sensor 910 e.g.: a pulse oximeter
  • the apparatus 900 comprises a sensory interface 1030 which is connected to the output of the oximeter 910.
  • the apparatus 900 further comprises an interface 1020 connected to the output of the gas analyzer 920.
  • the apparatus further comprises a valve controller 1010 having an output connected to the input of the valve 940.
  • the outputs of the sensory interface 1030, the gas analyzer interface 1020 are connected to inputs of a processor 1040.
  • Respective outputs of the processor are connected to a transceiver 1060 and a user interface device 1050.
  • the oximeter 910 and the sensory interface 1030 constitute the sensory system of the overall system.
  • the valve 940 and the valve controller 1010 constitute the valve system of the overall system.
  • the oximeter 910 may be fitted onto the end of a finger of the patient. It may comprise an infrared emitter and detector for measuring the oxygen saturation of the arterial blood of the patient in a conventional manner. In an alternative embodiment the oxygen saturation is derived from the minute volume response of the patient, such as respiration rate and/or depth.
  • the respiration rate/depth measurements may be based on the chest displacement (respiratory band using inductive or force measurement), or, alternatively, on the produced sounds (microphone) or on the flow.
  • the sensory interface 1030 and the gas analyzer interface 1020 may comprise analogue to digital converters and other signal processing means for filtering and removing noise from the output signals of the oximeter 910 and the gas analyzer 920 to provide digital signals indicating the gas content fed to the patient via the mask 930 and the arterial oxygen saturation to the processor 1040.
  • the patient is fitted with the cushioned mask 930 over their nose and mouth.
  • Pressurized gas is supplied to the mask 930 via the gas analyzer 920 and the valve 940.
  • Exhaled gas is also fed from the mask 930 via the valve 940 to be vented (not shown in the Figures) as in conventional non-invasive ventilators.
  • the patient is also fitted with a pulse oximeter 910 on their finger.
  • the gas analyzer 920 measures the gas
  • the output of the gas analyzer is provided to a gas analyzer interface 1020 in which the signal is digitized and cleaned up before being provided to the processor 1040.
  • the processor 1040 modulates the gas concentrations via the valve controller 1010 and valve 940.
  • the time period of the applied modulation comprises several breathing periods, such that there is sufficient time to let a new Pa02 level settle, but fast enough so that the pH remains constant.
  • the invention does not impose restrictions on the type of gas mixture modulation, e.g. the modulation of the partial pressures in the gas mixture can be gradual (e.g. sinusoidal), or can be step-wise (e.g. square wave).
  • the oxygen saturation of the patient is measured by the pulse oximeter, for example. This is synchronized with the modulation of the gas concentration such for each modulation cycle; a measurement of the oxygen saturation is taken. This reading is provided to the processor.
  • the processor 1040 determines the pH value of the patient's arterial blood from the change in the oxygen saturation for the specific oxygen concentration using the ODC as shown, for example in Figures 1 to 4.
  • the partial C0 2 pressure is then determined from the pH value according to a simplified and standardized form of the Henderson-Hasselbalch equation.
  • the response may be calibrated using blood gas analysis as reference. Relative decrease is most important.
  • the user interface device 1050 may provide the user with a display and/or an alarm system of warning light or audible alarm to indicate gas supply levels or a fault with the equipment. It may also allow user input of settings or rest by a health professional.
  • the determined pC0 2 pressure is output via the transceiver 1060, wirelessly, to a central computer system for analysis by health professionals.
  • the inspired oxygen fraction (Fi02) [%] in the supplied gas is slowly modulated over time via the valve controller 1010 and valve 940 as described above.
  • the inspired oxygen fraction in the applied gas is modulated such that the Pa02 is also modulated.
  • this measure does not change the respiration depth- or frequency and therefore the pH in the blood and thus the PaC02 remains constant.
  • the body tries to stabilize the pH by controlling the amount of HCO 3 " by adding or extracting HCO 3 " from the blood via the kidneys.
  • Sp02 monitors the fraction of haemoglobin that carries oxygen, i.e. the arterial oxygen saturation, which relates to the partial oxygen pressure via the ODC.
  • the response of the Sp02 sensor to the gas mixture modulation depends on the local slope of the ODC, which slope is indicative for the pH and thus for the partial arterial carbon dioxide pressure PaC02.
  • Figure 1 is illustrated that the dissociation curve shifts to the right side when the pH is decreased (increased pC02 level). This facilitates increased oxygen dumping. This mechanism allows for the body to adapt the problem of supplying more oxygen to tissues that need it the most.
  • the (FiC02) [%] in the supplied gas mixture is slowly modulated over time, e.g. by re-breathing the exhaled breath. This effectively modulates the arterial partial carbon dioxide pressure PaC02 and thus the pH.
  • the inspired oxygen fraction Fi02 is compensated for the slowly modulated inspired carbon dioxide fraction FiC02 [%] in the supplied gas mixture. This effectively modulates the PaC02 and thus the pH, while keeping Pa02 constant.
  • the modulated pH varies the Sp02 in a certain extend indicative for the nominal pH.
  • the overall is system is the same as that described above with respect to the first embodiment except that the apparatus 900 does not modulate the gas concentration.
  • the mixture (mutual concentration) of the gas supplied is varied by the valve 940 and valve controller 1210 in response to the output of the gas analyzer 920 to ensure the correct mixture is supplied to the patient (subject) according to their treatment.
  • the mixture of the gas supplied can be varied by the valve 940 and valve controller 1210 without a response from a gas analyzer.
  • the apparatus 900 comprises a sensory interface 1230 which is connected to the output of the oximeter 910.
  • the apparatus 900 further comprises an interface 1220 connected to the output of the gas analyzer 920.
  • the apparatus further comprises a valve controller 1210 having an output connected to the input of the valve 940.
  • the apparatus 900 further comprises a driver 1270 having an input connected to an output of the processor 1240 and an output connected to the oximeter 910.
  • the outputs of the sensory interface 1230, the gas analyzer interface 1220 are connected to inputs of a processor 1240. Further, respective outputs of the processor are connected to a transceiver 1260 and a user interface device 1250.
  • the sensor 910 and the sensory interface 1230 constitute the sensory system of the overall system.
  • the valve 940 and the valve controller 1210 constitute the valve system of the overall system.
  • the oximeter 910 may be fitted onto the end of a finger of the patient. It may comprise an infrared emitter and detector for measuring the oxygen saturation of the arterial blood of the patient in a conventional manner.
  • the driver 1270 produces the required duty cycles for driving the infrared emitter of the oximeter 910.
  • the sensory interface 1230 and the gas analyzer interface 1220 may comprise analogue to digital converters and other signal processing means for filtering and removing noise from the output signals of the oximeter 910 and the gas analyzer 920 to provide digital signals indicating the gas content fed to the patient via the mask 930 and the arterial oxygen saturation to the processor 1240.
  • the patient is fitted with the cushioned mask 930 over their nose and mouth.
  • Pressurized gas is supplied to the mask 930 via the gas analyzer 920 and the valve 940.
  • Exhaled gas is also fed from the mask 930 via the valve 940 to be vented (not shown in the Figures) as in conventional non-invasive ventilators.
  • the required gas concentrations for the subject condition are monitored by the gas analyzer 920 and the supply of gas is controlled via the valve system. This provides the patient (subject) with the correct mutual gas concentrations (mixture) in the mask for their treatment.
  • the subject is also fitted with a pulse oximeter 910 on their finger.
  • the processor 1240 modulates the temperature of the subject's skin on this finger, i.e. at the site of the oximeter 910 via the driver 1270 by varying the duty cycle of the currents supplied to the infra red emitter (e.g. LED).
  • the subject's finger may be heated and/or cooled by a separate blood-heating means such, for example, RF, electrical conductive, heater/cooler, Peltier elements etc.
  • the oxygen saturation of the patient is measured by the pulse oximeter, for example. This is synchronized with the modulation of the temperature such that, for each modulation cycle, a measurement of the oxygen saturation is taken. This reading is provided to the processor.
  • the processor 1240 determines the pH value of the patient's arterial blood from the change in the oxygen saturation for the specific oxygen concentration using the ODC as shown, for example in Figures 5 to 8.
  • the partial C0 2 pressure is then determined from the pH value according to a simplified and standardized form of the Henderson-Hasselbalch equation.
  • the calibration of the absolute pC02 level may be not necessary in case in case the application is limited to determination of the ventilation effectiveness overnight. In that case only the relative pC02 decrease is of importance as illustrated by Figure 5 to 8.
  • the user interface device 1250 may provide the user with a display and/or an alarm system of warning light or audible alarm to indicate gas supply levels or a fault with the equipment. It may also allow user input of settings or rest by a health professional.
  • the determined pC0 2 pressure is output via the transceiver 1260, wirelessly, to a central computer system for analysis by health professionals.
  • a combination is made of the features of the systems shown and described with reference to Figures 9, 10 and 11.
  • the apparatus 900 modulates both the gas concentration and the temperature at the site of measurement by the sensor 910 wherein the apparatus 900 performs all steps disclosed previously with regard to the systems shown and described with reference to Figures 9, 10 and 11.
  • the system comprises a modulator 1010 or 1210 for modulating at least one parameter of arterial blood of a subject; a sensory system 910, 1030, 1230 for deriving oxygen saturation of the arterial blood of said subject during modulation of said at least one parameter of arterial blood of said subject; and a processor 1040, 1240 for determining partial carbon dioxide pressure from said derived oxygen saturation.
  • Said system may further include a means 930, 950, 970 for supplying a pressurized gas to a subject, the pressurized gas comprising at least two gas components; and a valve system 940, 1010 for modulating concentrations of said at least two gas components.
  • Said system may further comprise a sensory system 910, 1030, 1230 for deriving oxygen saturation of the arterial blood of said subject wherein said sensory system further comprises a driver 1270 for driving a sensory device 910 of said sensory system to heat and/or cool the subject's arterial blood at the site of measurement for derivation of oxygen saturation.

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  • Pulmonology (AREA)
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Abstract

La pression partielle de dioxyde de carbone dans le sang artériel d'un sujet est déterminée par : modulation d'au moins un paramètre du sujet, tel que, par exemple, la concentration mutuelle des gaz administrés au sujet ou la température du sang artériel du sujet; dérivation de la saturation en oxygène du sang artériel dudit sujet; et détermination de la pression partielle de dioxyde de carbone à partir de ladite saturation en oxygène dérivée.
PCT/IB2011/055510 2010-12-10 2011-12-07 Procédé et appareil pour déterminer la pression partielle de dioxyde de carbone dans le sang artériel WO2012077065A1 (fr)

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WO2014198868A1 (fr) 2013-06-13 2014-12-18 Koninklijke Philips N.V. Dispositif et procédé pour déterminer une pression partielle de dioxyde de carbone chez un sujet d'intérêt
WO2016036519A1 (fr) * 2014-09-02 2016-03-10 General Electric Company Détermination de pression artérielle partielle de co2
WO2018106424A1 (fr) * 2016-12-05 2018-06-14 Medipines Corporation Système et procédés de mesures respiratoires utilisant des échantillons de gaz respiratoire
WO2018134823A1 (fr) * 2017-01-20 2018-07-26 Oridion Medical 1987 Ltd. Capteur double
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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014198868A1 (fr) 2013-06-13 2014-12-18 Koninklijke Philips N.V. Dispositif et procédé pour déterminer une pression partielle de dioxyde de carbone chez un sujet d'intérêt
CN105120751A (zh) * 2013-06-13 2015-12-02 皇家飞利浦有限公司 用于确定在感兴趣对象中的二氧化碳分压的设备和方法
WO2016036519A1 (fr) * 2014-09-02 2016-03-10 General Electric Company Détermination de pression artérielle partielle de co2
CN106659436A (zh) * 2014-09-02 2017-05-10 通用电气公司 动脉co2分压的测定
WO2018106424A1 (fr) * 2016-12-05 2018-06-14 Medipines Corporation Système et procédés de mesures respiratoires utilisant des échantillons de gaz respiratoire
CN110520043A (zh) * 2016-12-05 2019-11-29 梅迪平斯公司 使用呼吸气体样品进行呼吸测量的系统和方法
EP3838139A1 (fr) * 2016-12-05 2021-06-23 Medipines Corporation Dispositif de mesures respiratoires utilisant des échantillons de gaz respiratoire
US11154215B2 (en) 2016-12-05 2021-10-26 Medipines Corporation System and methods for respiratory measurements using breathing gas samples
WO2018134823A1 (fr) * 2017-01-20 2018-07-26 Oridion Medical 1987 Ltd. Capteur double
DE102017117681A1 (de) * 2017-08-03 2019-02-07 Fachkrankenhaus Kloster Grafschaft GmbH Überwachungseinrichtung und Verfahren zum Betreiben

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