RESPIRATORY PHYSIOLOGY

Hypoxic challenge flight assessments in patients with severe chest wall deformity or neuromuscular disease at risk for nocturnal hypoventilation

N Mestry¹, M Thirumaran¹, J M Tuggey¹, W Macdonald², M W Elliott¹

¹ Department of Respiratory Medicine, St James’s University Hospital, Leeds, UK
² Department of Pulmonary Physiology, St James’s University Hospital, Leeds, UK

Dr M W Elliott, Department of Respiratory Medicine, St James’s University Hospital, Beckett Street, Leeds LS9 7TF, UK; mwelliott{at}doctors.org.uk

Background: 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% and 95% with an additional risk factor, including kyphoscoliosis (KS) or neuromuscular disease (NMD). However, this recommendation was based on very few data.

Patients and methods: HCTs were performed on 19 adult patients with KS and/or NMD (age 22–73 years, forced expiratory volume in 1 s (FEV₁) 0.76, forced vital capacity (FVC) 0.92, SaO₂ 95%, partial pressure of arterial CO₂ (PaCO₂) 5.7 kPa) 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: The 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 SaO₂.

Conclusions: This finding suggests that all patients with severe extrapulmonary restrictive lung disease should undergo assessment with HCT prior to air travel. The study confirms that even patients with a resting saturation of >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 an HCT.

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