• Troy J Cross, Manda Keller-Ross, Amine Issa, Robert Wentz, Bryan Taylor, and Bruce Johnson.
• Heart Foundation Research Centre, Griffith Health Institute, Griffith University, Queensland, Australia.
• Sleep. 2015 Aug 1; 38 (8): 1331-4.

Study ObjectivesTo determine the impact of averaging window-length on the "desaturation" indexes (DIs) obtained via overnight pulse oximetry (SpO2) at high altitude.DesignOvernight SpO2 data were collected during a 10-day sojourn at high altitude. SpO2 was obtained using a commercial wrist-worn finger oximeter whose firmware was modified to store unaveraged beat-to-beat data. Simple moving averages of window lengths spanning 2 to 20 cardiac beats were retrospectively applied to beat-to-beat SpO2 datasets. After SpO2 artifacts were removed, the following DIs were then calculated for each of the averaged datasets: oxygen desaturation index (ODI); total sleep time with SpO2 < 80% (TST < 80), and the lowest SpO2 observed during sleep (SpO2 low).SettingSouth Base Camp, Mt. Everest (5,364 m elevation).ParticipantsFive healthy, adult males (35 ± 5 y; 180 ± 1 cm; 85 ± 4 kg).InterventionsN/A.Measurements And Results49 datasets were obtained from the 5 participants, totalling 239 hours of data. For all window lengths ≥ 2 beats, ODI and TST < 80 were lower, and SpO2 low was higher than those values obtained from the beat-to-beat SpO2 time series data (P < 0.05).ConclusionsOur findings indicate that increasing oximeter averaging window length progressively underestimates the frequency and magnitude of sleep disordered breathing events at high altitude, as indirectly assessed via the desaturation indexes.© 2015 Associated Professional Sleep Societies, LLC.

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