Examinations on the blood flow dependence of tcPO2 using the model of the "circulatory hyperbola"

The relation of transcutaneous pO2 (tcpO2) and cutaneous blood flow (CBF) was measured on the forearm of 19 healthy volunteers by use of a tcpO2 electrode heated to 45 degrees C. CBF was estimated indirectly from the heating power of the electrode (HP) and with a 8 MHz bidirectional ultrasonic probe by Doppler shift in a fingertip warmed to 45 degrees C (DF). Arterial blood flow was regulated by a cuff on the upper arm. The arterial flow was reduced in 10-15% stages of effective perfusion pressure Peff. There was a decrease in pO2 when CBF was restricted in stages as suggested by the model of the "circulatory hyperbola" according to Lübbers. A linear dependence between Peff, HP and DF was observed. These results indicate, that there is no autoregulation in the hyperemizied capillary bed. During respiration of air mean tcpO2 was 86.0 Torr (+/- 6.2) in normal blood flow conditions and reflects well paO2. Transcutaneous pO2 may also be used as a measure of CBF. To distinguish between these two modes, the determination of paO2 in capillary blood probes is necessary for calculating the transcutaneous index tcpO2/paO2.