Introduction Limited data are available comparing air travel with the hypoxic challenge test (HCT) in adults with cystic fibrosis (CF). The aim of this study was to assess the predictive capability the HCT to in-flight hypoxaemia in adult passengers with CF.

Methods Fifteen subjects (three male) volunteered for this study. Lung function measurements (FEV1) were performed pre and post flight. Oxygen saturation measured by pulse oximetry (SpO2) and symptoms were recorded in-flight on both outward and inward flights. The HCT was performed post flight and the in-flight oxygenation response was compared to the HCT and lung function results.

Results All subjects flew without the use of oxygen, and no adverse events were recorded in-flight. Air travel caused significant desaturation (p < 0.001) (mean pre flight SpO₂ 95+−1%; mean in-flight SpO₂ 90 ± 3%). The HCT caused mean desaturation (p ≤ 0.001) that was comparable to that of air travel (90 ± 3%). The pre flight FEV1 and in-flight SpO₂ showed weak correlation (r = 0.41 p = 0.125). The HCT SpO₂ showed strong correlation with in-flight SpO₂ (r = 0.74 p < 0.001). The HCT showed the strongest correlation with the lower SpO₂ value measured from both outward and inward flights (r = 0.92 p < 0.001).

Conclusions Significant in-flight desaturation can be expected in passengers with CF. The HCT results compare favourably with air travel data and may be considered the best widely available laboratory test to predict in-flight hypoxaemia in adults with CF.