Hypoxic challenge testing in idiopathic pulmonary fibrosis

The British Thoracic Society guidelines on air travel in patients with respiratory disease advocate individual risk assessment, with a respiratory physician being the central referral point. Hypoxic challenge tests (HCT) can identify patients that would benefit from in-flight oxygen, but evidence as to which patients is lacking. We aimed to identify parameters that might predict the outcome of a HCT in patients with idiopathic pulmonary fibrosis (IPF). 19 consecutive HCTs were reviewed. Data from patients requiring in-flight oxygen according to the HCT was compared to data from patients who did not. The patients were divided into 2 groups: Passed (10) - failed (9). Lung function parameters were taken and compared between the 2 groups. These data are presented in the table, and show that FEV1 SD, FVC SR, TLco % predicted, TLco SR and Kco SR were significantly different between the groups. Regression analysis was performed and a TLco SR below -3.4 was predictive of the requirement for supplemental in-flight oxygen. A TLco SR below -3.4 could be used to identify patients who require supplemental oxygen, but the numbers in our study are small. We recommend that the safest approach is to refer all patients with IPF for HCT assessment until more evidence-based data is available.