Introduction: In a British Thoracic Society (BTS) statement on preflight evaluation of patients with respiratory disease, sea level pulse oximetry (Spo2sl) is recommended as an initial assessment. The present study aimed to evaluate if the BTS algorithm can be used to identify chronic obstructive pulmonary disease (COPD) patients in need of supplemental oxygen during air travel, i.e. patients with an in-flight PaO2 < 6.6 kPa (50 mmHg).
Methods: There were 100 COPD patients allocated to groups according to the BTS algorithm: Spo2sl > 95%, Spo2sl 92-95% without additional risk factors; Spo2sl 92-95% with additional risk factors; Spo2sl < 92%; and patients using domiciliary oxygen. Pulse oximetry, arterial blood gases, and an hypoxia-altitude simulation test (HAST) to simulate a cabin altitude of 2438 m (8000 ft), were performed.
Results: The percentage of patients in the various groups dropping below 6.6 kPa during HAST were: Spo2sl > 95%: 30%; Spo2sl 92-95% without additional risk factors: 67%; Spo2sl 92-95% with additional risk factors: 70%; Spo2sl < 92%: 83%; and patients using domiciliary oxygen: 81%. In patients dropping below P(a)o(2) 6.6 kPa, supplemental oxygen of median 1 L x min(-1) was needed to exceed this limit.
Discussion: If in-flight P(a)o(2) > or = 6.6 kPa is regarded as a strict requirement, the use of pulse oximetry as an initial assessment in the preflight evaluation of COPD patients, as suggested by the BTS, might not discriminate adequately between patients who fulfill the indications for supplemental oxygen during air travel, and patients who can travel without such treatment.