The impact of averaging window length on the "Desaturation" indexes obtained via overnight pulse oximetry at high altitude

Troy J. Cross, Manda Keller-Ross, Amine Issa, Robert Wentz, Bryan Taylor, Bruce David Johnson

Research output: Contribution to journalArticle

5 Scopus citations


Study Objectives: To determine the impact of averaging window-length on the "desaturation" indexes (DIs) obtained via overnight pulse oximetry (SpO<inf>2</inf>) at high altitude. Design: Overnight SpO<inf>2</inf> data were collected during a 10-day sojourn at high altitude. SpO<inf>2</inf> 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 SpO<inf>2</inf> datasets. After SpO<inf>2</inf> artifacts were removed, the following DIs were then calculated for each of the averaged datasets: oxygen desaturation index (ODI); total sleep time with SpO<inf>2</inf> < 80% (TST < 80), and the lowest SpO<inf>2</inf> observed during sleep (SpO<inf>2</inf> low). Setting: South Base Camp, Mt. Everest (5,364 m elevation). Participants: Five healthy, adult males (35 ± 5 y; 180 ± 1 cm; 85 ± 4 kg). Interventions: N/A. Measurements and Results: 49 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 SpO<inf>2</inf> low was higher than those values obtained from the beat-to-beat SpO<inf>2</inf> time series data (P < 0.05). Conclusions: Our 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.

Original languageEnglish (US)
Pages (from-to)1331-1334
Number of pages4
Issue number8
StatePublished - Aug 1 2015



  • High altitude
  • Moving averages
  • Pulse oximetry
  • Sleep

ASJC Scopus subject areas

  • Physiology (medical)
  • Clinical Neurology

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