End-Tidal Partial Pressure of Carbon Dioxide and Acute Mountain Sickness in the First 24 Hours Upon Ascent to Cusco Peru (3326 meters)

Abstract

To explore the association of end-title partial pressure (Petco(2)) and oxygen saturation (Spo(2)) with the development of AMS in travelers rapidly ascending to Cusco, Peru (3326 m). Using the 715 TIDAL WAVE Sp handheld, portable capnometer/oximeter, we measured Spo(2) and Petco(2) in 175 subjects upon ascent to Cusco, Peru (3326 m) from Lima (sea level) (a mean time of 3.9 hours.) Symptoms of AMS were recorded at the same initial time on arrival to altitude and 24 hours later using the Environmental Symptoms Questionnaire (ESQ). This study showed that no subjects with the lowest Petco(2) of 23 to 30 mm Hg had AMS (P <.044). The data also demonstrate that subjects with a higher Petco(2) (36-40 mm Hg) and lower Sao(2) (72%-86%) have a higher incidence of AMS. The most important finding of this study is that Petco(2) upon ascent was found to have a more significant effect than Spo(2) on a subject's ultimate ESQ score. This study demonstrates that those individuals with a brisk ventilatory response upon ascent to moderate altitude, as measured by Petco(2), did not develop AMS, whereas a blunted ventilatory response, as reflected in the highest Petco(2), was related to the subsequent development of AMS.