Air travel and COPD: Exercise SpO ₂ and walking distance as predictors for in-flight desaturation

Background: Supplemental oxygen during air travel is recommended when in-flight PaO 2 is expected to fall below 6.6 kPa in patients with lung disease. Sea level oxygen saturation by pulse oximetry (SpO 2 ) alone has proven inadequate as a predictor of in-flight hypoxemia, and it has been suggested that exertional desaturation and walking capacity may provide useful additional information in the initial pre-flight assessment. Aim: The study aimed to evaluate if exertional desaturation and walking distance during a 6-min walk test (6MWT) might help predicting in-flight hypoxemia and thereby the need for in-flight oxygen in patients with COPD. Methods: COPD-patients referred to hypoxia-altitude simulation test (HAST) were consecutively included. Lung function tests, blood gas measurement, 6MWT, and HAST were performed. Results: 100 COPD patients (42% men) were included, mean (SD) age 65 (8) years, FEV 1 41 (13)% predicted. SpO 2 baseline was 93 (3)%, PaO 2 HAST 6.3 (0.6) kPa, and nadir SpO 2 6MWT 83 (6)%. Nadir SpO 2 6MWT and walking distance correlated with in-flight PaO 2 (r=0.49, p<0.001 and r=0.27, p=0.007, respectively). ROC analysis with nadir SpO 2 6MWT against PaO 2 HAST < 6.6 kPa gave an area under the curve of 0.786 and suggested that the cut-off yielding greatest accuracy for an in-flight PaO 2 < 6.6 kPa was a SpO 2 6MWT below 85% (sensitivity 85%, specificity 69%). Walking distance had no prognostic value for in-flight PaO 2 in the ROC analysis. Conclusions: In patients with COPD, exercise desaturation below 85% suggests that in-flight oxygen might be needed. As a supplement to sea level SpO 2 , exercise desaturation might be useful in the initial pre-flight screening.