Effects of Normobaric Hypoxia on Oxygen Saturation Variability.

The study is the first to evaluate the effects of graded normobaric hypoxia on SpO variability in healthy individuals. Twelve healthy males (mean [standard deviation] age 22 [4] years) were exposed to four simulated environments (fraction of inspired oxygen [O]: 0.12, 0.145, 0.17, and 0.21) for 45 minutes, in a balanced crossover design. Sample entropy, a tool that quantifies the irregularity of pulse oximetry fluctuations, was used as a measure of SpO variability. SpO entropy increased as the O decreased, and there was a strong significant negative correlation between mean SpO and its entropy during hypoxic exposure ( = -0.841 to -0.896,  < 0.001). In addition, SpO sample entropy, but not mean SpO, was correlated ( = 0.630-0.760,  < 0.05) with dyspnea in O 0.17, 0.145, and 0.12 and importantly, SpO sample entropy at O 0.17 was correlated with dyspnea at O 0.145 ( = 0.811,  < 0.01). These findings suggest that SpO variability analysis may have the potential to be used in a clinical setting as a noninvasive measure to identify the negative sequelae of hypoxemia.