title: The Impact of Averaging Window Length on the"Desaturation Indexes during Overnight Pulse Oximetry at High-Altitude".
abstract: OBJECTIVE
  To determine the impact of averaging window-length on the "desaturation" indexes (DIs) obtained via overnight pulse oximetry (SpO2) at high altitude.
  
  
  METHODS
  Overnight 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).
  
  
  METHODS
  South Base Camp, Mt. Everest (5,364 m elevation).
  
  
  METHODS
  Five healthy, adult males (35 ± 5 y; 180 ± 1 cm; 85 ± 4 kg).
  
  
  METHODS
  N/A.
  
  
  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 SpO2 low was higher than those values obtained from the beat-to-beat SpO2 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.
authors.affiliation: Heart Foundation Research Centre, Griffith Health Institute, Griffith University, Queensland, Australia.|Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN.
authors.forename: Troy J
authors.initials: TJ
authors.lastname: Cross
authors.affiliation: Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN.
authors.forename: Manda
authors.initials: M
authors.lastname: Keller-Ross
authors.affiliation: Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN.
authors.forename: Amine
authors.initials: A
authors.lastname: Issa
authors.affiliation: Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN.
authors.forename: Robert
authors.initials: R
authors.lastname: Wentz
authors.affiliation: Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN.
authors.forename: Bryan
authors.initials: B
authors.lastname: Taylor
authors.affiliation: Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN.
authors.forename: Bruce
authors.initials: B
authors.lastname: Johnson
mesh_terms: D000328:Adult; D000531:Altitude; D016477:Artifacts; D064368:Healthy Volunteers; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D010092:Oximetry / Q000295:instrumentation / Q000379:methods*; D010100:Oxygen / Q000378:metabolism; D017286:Polysomnography / Q000295:instrumentation; D012890:Sleep / Q000502:physiology; D012891:Sleep Apnea Syndromes / Q000175:diagnosis* / Q000503:physiopathology*; D013997:Time Factors
chemical_list: D010100:Oxygen
keywords: high altitude; moving averages; pulse oximetry; sleep