Effects of Normobaric Hypoxia on Oxygen Saturation Variability
Joseph T. Costello, Amar S. Bhogal, Thomas B. Williams, Richard Bekoe, Amin Sabir, Mike Tipton, Jo Corbett, Ali R. Mani
Abstract
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 [ F I O 2 ]: 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 F I O 2 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 F I O 2 0.17, 0.145, and 0.12 and importantly, SpO 2 sample entropy at F I O 2 0.17 was correlated with dyspnea at F I O 2 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.