Introduction Respiratory muscle weakness is a feature of motor neurone disease (MND), develops insidiously and presents with subtle symptoms. It can be difficult to assess in MND patients who, as a result, may be at risk of desaturation at altitude. Hypoxic challenge tests (HCT) can identify patients who would benefit from in-flight oxygen, but evidence as to which patients should be referred is lacking. The aim of this study was to identify factors that may predict the need for in-flight oxygen in this group of patients where maintaining their independence for as long as possible is paramount. Methods 81 consecutive HCT’s in 53 male, 28 female patients, and the contemporaneous assessments for respiratory muscle weakness on patients with MND. Data from patients requiring in-flight oxygen according to the HCT was compared to data from patients who did not, in accordance with the BTS Guidance for Air Travel 2011. Results The median patient age of patients who passed the HCT was 62 years; those that failed the HCT were significantly older with a median age of 68 years (p=0.009). There was a significant difference in baseline PaO 2 and PaCO 2 between the groups as shown in Table 1; patients who passed the HCT had higher baseline Pa02 and lower PaC02 (10.4 kPa and 5.3 kPa versus 9.3 kPa and 6.2 kPa respectively p=0.0001 and 0.0014). No other parameter, including BMI, smoking history, or physiological measurement including SNIP, or spirometry, could predict the outcome of the HCT. Conclusions Although MND patients that are likely to fail a HCT have a higher baseline C02, a threshold C02 value that could identify patients needing in-flight oxygen was not determined. We recommend that the safest approach is to refer all patients with MND that intend to fly for HCT assessment until more evidence-based data is available, which is the current practice at this regional centre.
