Abstract
Introduction
Acute mountain sickness (AMS) occurs in almost half of adults that ascend to 3048 m and three-quarters of adults that ascend to 4572 m. There is no accepted predictive test for AMS. This study explores a standardized way to predict risk for development of AMS.
Objectives
To study the development of AMS by testing if resting and post–3-min step test (TMST) oxygen saturation (SpO2) and heart rate (HR) measured at 4328 m on Denali have predictive value and identifying a threshold with high sensitivity for ruling out the risk of developing AMS.
Methods
We conducted a prospective observational study at Denali Camp IV (4328 m) during May-June 2022. Participation was voluntary and required no current AMS or other illness. Resting SpO2 and HR were measured using a Nonin Vantage 9590 pulse oximeter. Participants stepped on and off an 8-inch step for 3 min at 50% maximal exercise ability. Immediately after TMST, SpO2 and HR were measured. A postsurvey was sent to participants to screen for development of AMS.
Results
One hundred twenty-eight individuals participated in the study, completed the postsurvey, and met inclusion criteria. Twenty-one developed AMS upon further ascent (16.4%). Age (P=0.007), resting SpO2 (P=0.002) and HR (P=0.009), and postexercise SpO2 (P=0.021) and HR (P=0.002) were found to be statistically significant predictors. Receiver operating characteristic curve analysis found a percentage threshold for resting SpO2 of <89% (Sn, 0.81; P=0.0003), a percentage threshold for post-TMST SpO2 of <83% (Sn, 0.81; P=0.0046), a threshold for resting HR of >80 (Sn, 0.81; P=0.0104), and a threshold for post-TMST HR of >110 (Sn, 0.86; P=0.0052).
Conclusions
Measuring pre- and post-TMST SpO2 and HR for mountaineers at altitude may be a valid approach to rule out the risk of developing AMS. Individuals with a resting SpO2 >89% or HR <80 bpm and/or post-TMST SpO2 >83% or HR <110 bpm may be at lower risk for development of AMS upon continued ascent.
Keywords: altitude illness, exercise, predictive value of tests, heart rate, oxygen saturation, prospective studies
Winner of the Outstanding Research Presentation award at the WMS 2023 Summer Conference.