Predicting hypoxia in cystic fibrosis patients during exposure to high altitudes

AbstractBackgroundFor patients with cystic fibrosis (CF)-related partial respiratory insufficiency and reduced arterial oxygen tension at ground level, the mild hypobaric environment on commercial jet aircraft poses the risk of severe hypoxemia. Thus, physicians should be able to estimate the extent of in-flight hypoxia.ObjectivesTo derive tools for estimating the expected drop in arterial oxygen partial pressure (paO2) and oxygen saturation (saO2) in young adult CF patients with mild to moderate airway obstruction during exposure to the hypobaric conditions aboard commercial aircraft and to test the predictive power of a hypobaric chamber simulation.MethodsBlood gases of 12 CF patients were measured at ground level, at two altitudes in a hypobaric chamber (2000 and 3000 m) and during two 3.5-h flights at cabin altitudes of 1855 m and 1700 m. The altitude dependence of paO2 and saO2 in the chamber and during the flights was calculated and results were used to derive estimation equations for in-flight values.ResultsIn the chamber, saO2 decreased by 0.33% per 100 m vertical ascent, and this rate increased significantly at altitudes >2000 m. Predicted saO2 differed from in-flight value by