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

ObjectiveTo explore the association of end-title partial pressure (Petco2) and oxygen saturation (Spo2) with the development of AMS in travelers rapidly ascending to Cusco, Peru (3326 m).MethodsUsing the 715 TIDAL WAVE Sp handheld, portable capnometer/oximeter, we measured Spo2 and Petco2 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).ResultsThis study showed that no subjects with the lowest Petco2 of 23 to 30 mm Hg had AMS (P <.044). The data also demonstrate that subjects with a higher Petco2 (36–40 mm Hg) and lower Sao2 (72%–86%) have a higher incidence of AMS.ConclusionThe most important finding of this study is that Petco2 upon ascent was found to have a more significant effect than Spo2 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 Petco2, did not develop AMS, whereas a blunted ventilatory response, as reflected in the highest Petco2, was related to the subsequent development of AMS.