Resting arterial oxygen saturation and breathing frequency as predictors for acute mountain sickness development: a prospective cohort study.

INTRODUCTION

The study evaluated the predictive value of arterial oxygen saturation (SaO2) after 30-min hypoxic exposure on subsequent development of acute mountain sickness (AMS) and tested if additional resting cardio-respiratory measurements improve AMS prognosis.

METHODS

Fifty-five persons were exposed to a simulated altitude of 4,500 m (normobaric hypoxia, FiO2 = 12.5%). Cardio-respiratory parameters, SaO2, blood lactate, and blood pressure were measured after 30 min of exposure. AMS symptoms were recorded after 3, 6, 9, and 12 h (Lake-Louise Score). Three models, based on previously published regression equations for altitude-dependent SaO2 values of AMS-susceptible (SaO2-suscept = 98.34 - 2.72 ∗ alt - 0.35 ∗ alt(2)) and AMS-resistant (SaO2-resist = 96.51 + 0.68 ∗ alt - 0.80 ∗ alt(2)) persons, were applied to predict AMS. Additionally, multivariate logistic regression analyses were conducted to test if additional resting measurements improve AMS prediction.

RESULTS

The three models correctly predicted AMS development in 62%, 67%, and 69% of the cases. No model showed combined sensitivity and specificity >80%. Sequential logistic regression revealed that the inclusion of tidal volume or breathing frequency in addition to SaO2 improved overall AMS prediction, resulting in 78% and 80% correct AMS prediction, respectively.

CONCLUSION

Non-invasive measurements of SaO2 after 30-min hypoxic exposure are easy to perform and have the potential to detect AMS-susceptible individuals with a sufficient sensitivity. The additional determination of breathing frequency can improve success in AMS prediction.