Does a change in end-tidal carbon dioxide level predict high altitude mountain sickness?

Area of Science:

• Altitude Medicine
• Physiology
• Respiratory Medicine

Background:

• Hypoxic ventilatory response is a potential predictor of acute mountain sickness (AMS).
• End-tidal carbon dioxide (ETCO2) offers a noninvasive method to assess ventilation.

Purpose of the Study:

• To investigate if changes in baseline ETCO2 predict the onset of AMS.
• To compare the predictive power of ETCO2 versus altitude for AMS development.

Main Methods:

• Prospective cohort study involving hikers on high-altitude treks.
• Collected ETCO2 measurements at base, various elevations, and summit.
• Assessed AMS using a standardized scoring system by trained investigators.
• Analyzed data using correlation coefficients and linear regression.

Main Results:

• 21 subjects participated across three different high-altitude hikes.
• A decrease in ETCO2 was moderately correlated with AMS development (r=-0.46).
• ETCO2 showed a strong correlation with altitude (r=-0.77).
• ETCO2 was a superior predictor of AMS compared to altitude (AUC 0.90 vs. 0.64).
• ETCO2 ≤22 mmHg demonstrated 100% sensitivity and 60% specificity for predicting AMS.

Conclusions:

• ETCO2 is strongly correlated with altitude and moderately correlated with AMS.
• ETCO2 serves as a more effective predictor of AMS than altitude.
• Monitoring ETCO2 may aid in assessing AMS risk in high-altitude environments.