Walking capacity and fitness to fly in patients with chronic respiratory disease

Introduction: In this study, we tested the hypothesis that walking capacity, assessed by the 6-min walk test (6MWT), could be related to the effect of flight simulation at sea level obtained by the hypoxiaaltitude simulation test (HAST) in patients with chronic respiratory disease. Methods: There were 15 patients with interstitial lung disease and 15 patients with chronic obstructive pulmonary disease who were recruited. Their baseline SpO2 values ranged from 88 to 98%. All patients performed the 6MWT and HAST according to standardized methods. Results: Patients covered a walking distance ranging from 185 to 592 m without stopping while experiencing no to severe dyspnea. No correlation was found between dyspnea perception during walking, walking distance, and oxygen desaturation during HAST. The oxygen desaturation induced by the 6MWT was related to that after HAST (r 0.52, p 0.01). The bias and limits of agreement between the oxygen desaturation after the 6MWT and after the HAST were 0.8 and 6.6 to 8.2%, respectively. The baseline SpO2 could reliably predict the oxygen desaturation during HAST (r2 0.51). Conclusions: Our results showed that measurement of SpO2 during 6MWT can provide useful information for the preflight assessment and the in-flight oxygen prescription of patients with chronic respiratory disease. Keywords: fitness to fly, hypoxia-altitude simulation test, 6-min walk test, interstitial lung disease, chronic obstructive pulmonary disease.