Sex-linked difference in blood oxygen saturation

Background: It is not known whether SpO₂ in healthy volunteers is affected by sex. Objective: To evaluate whether there are differences in SpO₂ between young healthy adult males and females and to evaluate whether the differences are already present at birth. Methods: We studied two cohorts of patients. The first one consisted of young adult volunteers (105 males and 102 females). In these patients, SpO₂ was measured as well as selected anthropometric variables (height, weight), vital signs (respiratory rate, pulse rate and body temperature) and obtained data on menstrual cycle phase of the female participants. For the second cohort, we reanalyzed data from a previous prospective study that was performed to compare SpO₂ of newborns infants born at different altitudes (sea level or 760 m above sea level). Measurements and main results: In young male adults, mean SpO₂ was 97.1% ± 1.2% versus 98.6% ± 1.0% in females (P <.001). This difference remained significant (P =.002) after correction for BMI, BSA and age, variables that were significantly different between sexes in univariate analysis. The SpO₂ in females was unaffected by menstrual phase. In contrast to findings in adults, there were no significant differences in SpO₂ measurements in newborn infants attributable to sex. Conclusions: Healthy young female adults have a higher (1.5%) SpO₂ than their male counterparts. This difference is not yet present at birth. Further studies are needed to determine the timing of sex-differences, and to better define the mechanism(s) behind this observation.