Dynamic Changes of Perfusion Index During Hypoxemia and Hypercapnia in Outdoor Experiments

Perfusion index (PI) derived from pulse oximetry is a well-recognized parameter for assessment of perfusion changes in peripheral tissues under different conditions. In outdoor breathing experiments with simulated avalanche snow, the subjects experience hypoxemia and hypercapnia due to significant rebreathing of the exhaled gas. In order to assess the behavior of the perfusion index during short-time hypoxemia and hypercapnia in these experiments, data from 13 healthy volunteers breathing into materials simulating avalanche snow were analyzed. The baseline perfusion index of the subjects at rest was 1.54+/-1.01. In the course of the experiment, despite the progressing hypoxemia and hypercapnia, there are no statistically significant changes in PI observed, followed by a rapid surge shortly after the subjects started to breathe ambient air and the hypercapnia prevailed over the vanishing hypoxemia. These results suggest that regardless of the hypoxemia and ambient environment, the perfusion of the peripheral tissues assessed by the pulse oximetry is sufficient during these experiments, presumably due to the vasodilatory effect of the hypercapnia.