비침습적 산소 및 이산화탄소 분압의 감시 - 경피적 산소 및 이산화탄소 분압과 호기말 이산화탄소 분압 측정의 정확도 -

Abstract

Purpose: To determine the concordance of transcutaneous CO₂ (PtcCO₂) versus arterial CO₂ (PaCO₂), end-tidal CO₂ (PetCO₂) versus PaCO₂, and transcutaneous O₂ (PtcO₂) versus arterial O₂ (PaCO₂) among healthy adult volunteers, and to determine the normal values of the PtcCO₂/PtcO₂ and PtcO₂/PaO₂ that will be used as early signs of shock or as prognostic factors for critically ill patients. Methods: We measured the PtcO₂, PtcCO₂, PetCO₂, PaO₂, and PaCO₂ from 11 healthy volunteers while breathing room air or O₂ at a flow rate of 6 L/min via nasal cannula. The PtcO₂ and PtcCO₂ were measured using a Radiometer’'s transcutaneous sensor that interfaced with the Solar 8000 patient monitor system. The PetCO₂ was measured using a side stream capnometer that sampled air from a nasal catheter. The PaO₂ and PaCO₂ were measured from arterial blood samples. The concordances of the PtcCO₂ versus the PaCO₂, the PtcO₂ versus the PaO₂, and the PetCO₂ versus the PaCO₂ were analyzed using a Bland-Altman plot. We defined the normal values of the P(a-tc)CO₂, PtcO₂/PaO₂, and PtcCO₂/PtcO₂. Results: Twenty-two pairs of the PtcCO₂ versus PaCO₂, PtcO₂ versus PaO₂, and PetCO₂ versus PaCO₂ were obtained. The mean (±SD) values of the P(a-tc)CO₂, P(atc) O₂, and P(a-et)CO₂ were 0(±2.2) mmHg, 35.4(±24.1) mmHg, and 1.4(±1.3) mmHg, respectively (p=0.947, p<0.001, and p<0.001 by paired t-test, respectively). The P(a-tc)CO₂ and P(a-et)CO₂ showed a high concordance of 95.5% within a range of ±4 mmHg. The median (25~75%) values of the PtcCO₂/PtcO₂ and PtcO₂/PaO₂ at room air were 54.8%(46.8%~6₂.7%), respectively. Conclusion: The PtcCO₂ and PetCO₂ had a reliable concordance with the PaCO₂. However, the PtcO₂ was discordant with the PaO₂ and this discordance was increased when inspiring O₂. Therefore, the absolute values of the PtcO₂ cannot be used as a surrogate measurement of the PaO₂. However, because the O₂ supply did not increase the PtcCO₂, but rather the PtcO₂, we can use the trend in the change in the PtcCO₂/PtcO₂ or PtcO₂/PaO₂ in shock patients