Transcutaneous oxygen monitoring1

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The technology to measure noninvasively the partial pressure of oxygen at the skin surface (“transcutaneous” PO2, or PtcO2) is now commercially available. In patients with normal cardiac output and cutaneous blood flow, the PtcO2 accurately monitors changes in the arterial partial pressure of oxygen (PaO2). However, if the cardiac output is reduced, the PtcO2 diverges from PaO2 and reflects tissue oxygen delivery instead. Thus, the physiologic interpretation of the PtcO2 varies according to the hemodynamic status of the patient. This limits the utility of transcutaneous oxygen monitoring in critically ill patients, but such monitoring can be useful in the noninvasive detection of adverse changes in arterial oxygenation or tissue perfusion.