Defining hypoxemia from pulse oximeter measurements of oxygen saturation in well children at low altitude in Bangladesh: an observational study

Background The World Health Organization defines hypoxemia, a low peripheral oxyhemoglobin saturation (SpO2), as <90%. Although hypoxemia is an important risk factor for mortality of children with respiratory infections, the optimal SpO2 threshold for defining hypoxemia is uncertain in low-income and middle-income countries (LMICs). We derived a SpO2 threshold for hypoxemia from well children in Bangladesh residing at low altitude. Methods We prospectively enrolled well, 3-35 month old children participating in a pneumococcal vaccine evaluation in Sylhet district, Bangladesh between June and August 2017. Trained health workers conducting community surveillance measured the SpO2 of children using a Masimo Rad-5® pulse oximeter with a wrap sensor. We used standard summary statistics to evaluate the SpO2 distribution, including whether the distribution differed by age or sex. We considered the 2.5th, 5th, and 10th percentiles of SpO2 as possible lower thresholds for hypoxemia. Results Our primary analytical sample included 1,470 children (mean age 18.6 +/- 9.5 months). Median SpO2 was 98% (interquartile range, 96–99%), and the 2.5th, 5th, and 10th percentile SpO2 was 91%, 92%, and 94%. No child had a SpO2 <90%. Children 3– 11 months old had a lower median SpO2 (97%) than 12–23 month olds (98%) and 24– 35 month olds (98%) (p=0.039). The SpO2 distribution did not differ by sex (p=0.959). Conclusion A SpO2 threshold for hypoxemia derived from the 2.5th, 5th, or 10th percentile of well children is higher than <90%. If a higher threshold than <90% is adopted into LMIC care algorithms then decision-making using SpO2 must also consider the child’s clinical status to minimize misclassification of well children as hypoxemic. Younger children in lower altitude LMICs may require a different threshold for hypoxemia than older children. Evaluating the mortality risk of sick children using higher SpO2 thresholds for hypoxemia is a key next step. Key Messages ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Trial The study did not meet the definition of a clinical trial. ### Funding Statement This study is funded by the Bill & Melinda Gates Foundation [OPP1084286, OPP1117483] and GlaxoSmithKline [90063241]. EDM was also supported by the Fogarty International Center of the National Institutes of Health under Award Number K01TW009988 for the research reported in this publication. The content is solely the responsibility of the authors and does not necessarily represent the official views of the Bill & Melinda Gates Foundation, GlaxoSmithKline or the National Institutes of Health. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The studys protocol was approved by the Johns Hopkins Bloomberg School of Public Health, Johns Hopkins School of Medicine, Bangladesh Institute of Child Health, and the Ethical Review Committee of the International Centre for Diarrhoeal Diseases Research, Bangladesh, Institutional Review Boards. Written informed consent was obtained from all participant caregivers. All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Deidentified participant data is available for sharing upon written request and completion of signed data sharing agreements to Dr. Eric D. McCollum at emccoll3{at}jhmi.edu.