Device and method for transcutaneous determination of blood gases
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Publication Number
US-8527023-B2
Publication Date
2013-09-03
Expiration Date
Abstract
The device for the transcutaneous determination of blood gases including a transcutaneous sensor for the measurement of at least one of the parameters of skin carbon dioxide partial pressure (PsCO2) and skin oxygen partial pressure (PsO2) includes at least one sensor for the measurement of the tissue blood flow (F) local with respect to the transcutaneous sensor, and includes a device for the calculation of at least one of the parameters of transcutaneous carbon dioxide partial pressure (tcpCO2) and transcutaneous oxygen partial pressure (tcpO2) from the measured skin carbon dioxide partial pressure (PsCO2) or the measured skin oxygen partial pressure (PsO2), with a factor dependent on the local tissue blood flow (F) being taken into account in the calculation of at least one of the parameters of transcutaneous carbon dioxide partial pressure (tcpCO2) and transcutaneous oxygen partial pressure (tcpO2).
Core Innovation
Transcutaneous determination of blood gases is improved by measuring skin carbon dioxide partial pressure (PsCO2) and/or skin oxygen partial pressure (PsO2) with a transcutaneous sensor and by locally measuring tissue blood flow (F) in relation to the transcutaneous sensor. The transcutaneous carbon dioxide partial pressure (tcpCO2) and/or the transcutaneous oxygen partial pressure (tcpO2) are calculated from the measured skin partial pressure values while taking into account a factor dependent on the local tissue blood flow (F).
For tcpCO2, the calculation takes place in accordance with an equation using Ts, Tr, A, and a metabolic offset Ms(F) that depends on F. In particular, tcpCO2 is determined as a function of the tissue blood flow (F) in accordance with tcpCO2(Tr,F)=PsCO2(Ts)·10^(Ts−Tr)·A−Ms(F). This links measured skin CO2 partial pressure (PsCO2) to a flow-dependent metabolic offset term Ms(F) while accounting for temperature-related parameters in the equation.
For tcpO2, transcutaneous oxygen partial pressure is calculated while taking into account the local tissue blood flow (F), including use of a correction factor dependent on flow. Tissue blood flow (F) is measured with at least one sensor configured with local proximity relative to the transcutaneous sensor and can be obtained using pulse oximetry, pulse spectroscopic/(photo)plethysmography, Doppler-based sensing, or heating-power based estimation.
Claims Coverage
The partial content identifies four independent claims: clm-00001, clm-00013, clm-00024, and clm-00025. Across these claims, the coverage centers on measuring skin partial pressures (PsCO2 and/or PsO2), locally measuring tissue blood flow (F), and calculating transcutaneous carbon dioxide partial pressure (tcpCO2) and/or transcutaneous oxygen partial pressure (tcpO2) with a factor dependent on F using specified equations and/or correction factors. Main inventive features are: flow-dependent tcp calculation models, dedicated tissue blood-flow measurement local to the transcutaneous sensor, and specific sensor/measurement modalities tied to determining F and computing tcpCO2.
Transcutaneous sensor with flow-dependent tcp calculation
A device with a transcutaneous sensor measuring skin carbon dioxide partial pressure (PsCO2) and/or skin oxygen partial pressure (PsO2), at least one sensor measuring local tissue blood flow (F) local with respect to the transcutaneous sensor, and calculation of tcpCO2 and/or tcpO2 from the measured PsCO2 and/or PsO2, taking into account a factor dependent on the local tissue blood flow (F), wherein tcpCO2 is calculated in accordance with tcpCO2(Tr,F)=PsCO2(Ts)·10^(Ts−Tr)·A−Ms(F).
Method with flow-dependent tcpCO2 equation
A method comprising detecting at least one of PsCO2 and PsO2, detecting a local tissue blood flow (F), and calculating tcpCO2 and/or tcpO2 from the measured PsCO2 and/or PsO2, taking F into account in the calculation, wherein tcpCO2 is calculated as a function of tissue blood flow (F) in accordance with tcpCO2(Tr,F)=PsCO2(Ts)·10^(Ts−Tr)·A−Ms(F).
SpO2-based flow determination for tcpCO2 calculation
A method using a sensor including a transcutaneous sensor for PsCO2 and a sensor for pulse spectroscopic or pulse oximetric measurement of arterial oxygen saturation (SpO2), determining local tissue blood flow (F) using the pulse spectroscopic/oximetric measurement while calculating tcpCO2 from the measured PsCO2, taking into account local tissue blood flow (F) in accordance with tcpCO2(Tr,F)=PsCO2(Ts)·10^(Ts−Tr)·A−Ms(F).
Heating device and pulse oximetry/spectroscopy integrated flow determination for tcpCO2
A method using a sensor including a transcutaneous sensor for PsCO2, a sensor for pulse spectroscopic or pulse oximetric measurement of arterial oxygen saturation (SpO2), and a heating device, comprising calculating local tissue blood flow (F) where at least the pulse spectroscopic/oximetric measurement and/or the heating device is taken into account for the determination of F, and calculating tcpCO2 from the measured PsCO2 taking into account the local tissue blood flow (F), wherein the sensor for measuring F detects a region up to 2 cm distance from a contact surface of the transcutaneous sensor.
The independent claims collectively require transcutaneous measurement of skin partial pressures and local measurement of tissue blood flow (F), followed by computation of transcutaneous pressures using a flow-dependent model. For tcpCO2, the computation is anchored on an explicit equation tcpCO2(Tr,F)=PsCO2(Ts)·10^(Ts−Tr)·A−Ms(F), with Ms(F) providing the flow-dependent adjustment. The independent claims further differentiate by how F is obtained, including integration of pulse spectroscopic/pulse oximetric SpO2 measurement and/or heating-device involvement, with spatial constraints on the region used for flow sensing.
Stated Advantages
Reduced deviations versus arterial values when using flow-corrected metabolic offset Ms(F) and temperature-dependent variants in the transcutaneous carbon dioxide calculation.
Improved agreement with arterial values for transcutaneous pressure determination when incorporating local tissue blood flow (F) into the calculation model.
Documented Applications
Transcutaneous blood-gas monitoring by determining tcpCO2 and/or tcpO2 for comparison with arterial partial pressures (e.g., PaCO2/PaO2), using flow-dependent correction in the tcp calculation.
Flow measurement integration with pulse oximetry/pulse spectroscopic/(photo)plethysmography, Doppler-based sensing, or heating-power-based estimation to provide tissue blood flow (F) used for transcutaneous blood gas calculations.
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