Introduction

Current UK guidelines recommend administration of in-flight supplemental oxygen to patients with chronic respiratory disease who have sea level arterial oxygen saturations <92% or partial pressure of oxygen (Pao₂) <6.6 kPa (50 mm Hg) during a hypoxic challenge fitness to fly test.1 Hypoxia has been shown to prolong cardiac repolarisation, assessed by the QT interval corrected for heart rate (QT_c), and this may underlie the occurrence of potentially life-threatening cardiac arrhythmias2–4; however, few data exist about the cardiac response to hypoxia in patients with respiratory disease.

To establish whether hypoxia prolongs the QT_c, potentially increasing the risk of significant arrhythmias in patients with respiratory disease, we analysed data from respiratory patients referred to our lung function department for fitness to fly testing. …