Normobaric hypoxia inhalation test vs. response to airline flight in healthy passengers

Introduction: There is little data available to determine the normal response to normobaric hypoxia inhalation testing (NHIT) and air travel. Quantifying a healthy response may assist in the evaluation of passengers considered at risk for air travel. The aims of this study were: 1) to quantify the degree of desaturation in healthy subjects during a NHIT and air travel; and 2) assess the validity of the NHIT when compared with actual in-flight responses. Methods: There were 15 healthy adults (age 23-57; 10 women) who volunteered for this study. Preflight tests included lung function, arterial blood gas, pulse oximetry (SpO₂), and NHIT (inspired oxygen 15%). SpO₂ and cabin pressure were measured continuously on each subject during a commercial air flight (mean cabin altitude 2178 m; range 1719-2426 m). In-flight oxygenation was compared with the preflight NHIT. Results: Lung function testing results were normal. There was significant desaturation (SpO₂) during the NHIT (pre: 98 ± 2%; post: 92 ± 2%) and at cruising altitude (pre: 97 ± 1%; cruise: 92 ± 2%). There was no difference between the final NHIT SpO₂ and the mean in-flight SpO₂. There was a significant difference between the lowest in-flight SpO₂ (88 ± 2%) vs. the lowest NHIT SpO₂ (90 ± 2%). Discussion: Oxygen saturation decreases significantly during air travel in normal individuals. In this group of healthy passengers the NHIT approximates some, but not all, aspects of in-flight oxygenation. These results can be used to describe a normal response to the NHIT and air-travel.