The British Thoracic Society (BTS) recommendations for patients with respiratory disease planning air travel suggest that an oxygen saturation (SaO2) >95% precludes the need for any further assessment of the need for supplemental oxygen during flight. A Hypoxic Challenge Test (HCT) is recommended for patients with a resting SaO2 between 92-95% with an additional risk factor, including kyphoscoliosis (KS) or neuromuscular disease (NMD). However this recommendation was based on very little data.
We performed HCTs on 19 adult patients with KS and/or NMD, (age 22-73 years, FEV1 0.76 FVC 0.92, SaO2 95%, PaCO2 5.7kPa) who were at risk for nocturnal hypoventilation. 15 were home ventilator users. Arterial blood gas measurements were made before and at the end of the hypoxic challenge.
Results of HCTs show that the majority (15 of 19) of this cohort of patients met the criteria suggested by the BTS Standards of Care Committee for in flight oxygen regardless of baseline oxygen saturation. This finding suggests that all patients with severe extrapulmonary restrictive lung disease should undergo assessment with Hypoxic Challenge Tests prior to air travel. The study confirms that even patients with a resting saturation of greater than 95% can desaturate significantly during hypoxic challenge. This study does not address the question of whether desaturation at altitude has any adverse consequences for patients. A decision as to whether it is safe for a patient to fly should be made by an experienced clinician and based on a number of factors, which should include previous travel experience, the patient’s overall condition and the results of a hypoxic challenge test.