Positive end expiratory pressure as a method for preventing acute mountain sickness

Abstract

In order to study the use of positive end expiratory pressure (PEEP) to prevent acute mountain sickness (AMS), 22 subjects were exposed randomly to 8-h hypobaric hypoxia in a hypobaric chamber (4500 m, 589 hPa, 22°C) once being administered 5-cm H₂O PEEP and once without. The prevention of AMS by PEEP was evaluated by scoring AMS according to the Lake Louise system (self-report questionnaire and clinical assessment) throughout the experiment with O₂ saturation (SO₂) and heart rate measurements being made. Arterial blood analyses (partial pressures of arterial O₂ and CO₂, P _aO₂, P _aCO₂, and pH) were made at the end of the exposure. Results showed decreased AMS scores with PEEP at the end of the 8-h hypoxia [1.50 (SEM 1.32) vs 3.23 (SEM 2.07), P < 0.01 for self-report plus clinical assessment scores] with a lower prevalence (23% vs 55%, P < 0.01). The SO₂, P _aO₂, P _aCO₂ and HCO₃ ⁻ did not change significantly. However, a smaller increase in arterial pH [7.47 (SEM 0.02) vs 7.50 (SEM 0.02), P < 0.05] was observed with PEEP, attesting a lesser alkalosis. Moreover, heart rate increased with PEEP (P < 0.05). In conclusion, this study would suggest that a 5-cm H₂O PEEP may help decrease AMS scores at the end of an 8-h exposure to hypoxia in a hypobaric chamber. Such a method could be used to prevent AMS in such experimental conditions without adverse effects.