Hypoxic challenge testing in motor neurone disease

British Thoracic Society guidance on air travel in patients with respiratory disease advises that a hypoxic challenge test (HCT) can be used to determine the need for in-flight oxygen in patients at high risk of medical complications. Evidence to inform the clinician as to which patients are high-risk, particularly disease-specific evidence, is lacking. We present a case series of 40 patients with motor neurone disease (MND) referred for hypoxic challenge testing. We aimed to identify parameters that might predict the outcome of an HCT in patients with MND to aid clinicians undertaking pre-flight assessments. An HCT was performed and capillary blood gas measurements, spirometric data and sinus nasal inspiratory pressure measurements were obtained. Data from those patients requiring in-flight oxygen according to the HCT was compared to data obtained from patients who did not and results are summarised below. According to our data, baseline paCO2 was the only independent predictor of hypoxaemia following an HCT. Our data also suggests that inability to perform spirometry and need for home non-invasive ventilation reflect disease severe enough to warrant an HCT as part of a pre-flight assessment.