Noninvasive PtcO2 initial slope index and invasive PtcO2 arterial index as diagnostic criterion of the state of peripheral circulation.

: Transcutaneous PO2 (PtcO2), PaO2, PtcO2 arterial index (ARI; PtcO2/PaO2), and the initial slope index (ISI; [delta PO2/min]/starting PtcO2) were measured in 42 healthy volunteers, 12 patients with stable circulation and respiratory insufficiency, and ten patients with insufficient peripheral circulation in cardiogenic shock in order to investigate whether ARI and ISI can be used to detect insufficient circulation. The ISI was measured by placing a PtcO2 electrode on the forearm and interrupting blood flow by inflating a cuff until the PtcO2 dropped to zero. After releasing the cuff pressure, the initial slope of the PtcO2 trace was determined in order to calculate the ISI. In the PtcO2 range between 40 and 100 torr, the ARI and ISI did not depend on the PtcO2 magnitude. In all groups, the ISI behaved similarly to the ARI. We conclude that the noninvasive ISI and invasive ARI are able to differentiate between stable and insufficient peripheral circulation (ISI less than 0.75, ARI less than 0.8; p less than .001).