Effect of Oxygen Concentration Reduction on Photoplethysmographic Waveform Characteristics

This paper aims to find out the difference of human photoplehysmography (PPG) morphological parameter K between in normal oxygen concentration regions and in low oxygen level environments. We implemented an experiment with a normobaric hypoxic chamber which generalized low oxygen level environment of 13.4% (equivalent to the altitude of 3600 m). The experiment contained two sections-10 minutes short exposure and a night of sleep. Fingertip PPG signal was recorded in the whole process. We carried out a comparative analysis for each subject in normal and hypoxic conditions. Result showed that the average K values in normoxic environment and hypoxic conditions for short exposure were 0.3456 and 0.3861 respectively, and for sleep were 0.3081 and 0.3419 respectively. Significance level p were both less than 0.05. Variations of PPG waveform parameter K reflect the changed peripheral vascular resistance. In hypoxic environment, the raised K value tallied with the physiological mechanism that hypoxic exposure increases peripheral vascular resistance. And this phenomenon happened since the beginning of hypoxia and could last for at least a night.