Oxygen Saturation in Childhood at High Altitude: A Systematic Review

Background: It is well known that oxygen saturation as measured by pulse oximetry (SpO₂) decreases as altitude increases. However, how SpO₂ changes across childhood, and more specifically during sleep/wake states, at different high altitudes are less well understood. We aimed to perform a systematic review of all studies with direct SpO₂ measurement in healthy children living at high altitude (>2500 meters above sea level) to address these questions. Methods: MEDLINE, EMBASE, and SciELO databases were searched up to December 2018. Two independent reviewers screened the literature and extracted relevant data. Results: Of 194 references, 20 studies met the eligibility criteria. Meta-analysis was not possible due to the use of different oximeters and/or protocols for data acquisition and reporting of different SpO₂ central tendency and dispersion measures. The most relevant findings from the data were: (1) SpO₂ is lower as altitude increases; (2) at high altitude, SpO₂ improves with age through childhood; (3) SpO₂ is lower during sleep and feeding in comparison to when awake, this SpO₂ gap between wake and sleep states is more evident in the first months of life and narrows later in life; (4) SpO₂ dispersion (interindividual variation) is higher at younger ages, and more so during sleep; (5) In 6/20 studies, the SpO₂ values were nonnormally distributed with a consistent left skew. Conclusions: At high altitude, the mean/median SpO₂ increases in children with aging; a significant gap between wake and sleep states is seen in the first months of life, which narrows as the infant gets older; SpO₂ dispersion at high altitude is wider at younger ages; at high altitude, SpO₂ shows a nonnormal distribution skewed to the left; this bias becomes more evident as altitude increases, at younger ages and during sleep.