Effects of Normobaric Hypoxia on Oxygen Saturation Variability

Costello, Joseph T., Amar S. Bhogal, Thomas B. Williams, Richard Bekoe, Amin Sabir, Michael J. Tipton, Jo Corbett, and Ali R. Mani. Effects of normobaric hypoxia on oxygen saturation variability. High Alt Med Biol 00:000-000, 2020. Background: The study is the first to evaluate the effects of graded normobaric hypoxia on SpO(2) variability in healthy individuals. Materials and Methods: Twelve healthy males (mean [standard deviation] age 22 [4] years) were exposed to four simulated environments (fraction of inspired oxygen [FIO2]: 0.12, 0.145, 0.17, and 0.21) for 45 minutes, in a balanced crossover design. Results: Sample entropy, a tool that quantifies the irregularity of pulse oximetry fluctuations, was used as a measure of SpO(2) variability. SpO(2) entropy increased as the FIO2 decreased, and there was a strong significant negative correlation between mean SpO(2) and its entropy during hypoxic exposure (r = -0.841 to -0.896, p < 0.001). In addition, SpO(2) sample entropy, but not mean SpO(2), was correlated (r = 0.630-0.760, p < 0.05) with dyspnea in FIO2 0.17, 0.145, and 0.12 and importantly, SpO(2) sample entropy at FIO2 0.17 was correlated with dyspnea at FIO2 0.145 (r = 0.811, p < 0.01). Conclusions: These findings suggest that SpO(2) variability analysis may have the potential to be used in a clinical setting as a noninvasive measure to identify the negative sequelae of hypoxemia.