Can baseline lung function and arterial oxygenation predict air travel hypoxaemia in respiratory patients

Introduction: Individuals with respiratory disease are at risk of hypoxaemia during air travel. Several methods have been used, however, the hypoxic challenge testing (HCT) is nowadays the preferred method to predict it. The relation between air travel hypoxaemia, baseline lung function tests (LFT) and arterial oxygenation has been studied with discrepant data. Aim: Assess the correlation between PaO2 on HCT and LFT, resting sea level PaO2 and SpO2. Methods: Included all respiratory patients who performed LFT and HCT between January 2016 and December 2017 at Hospital da Luz Lisboa (private hospital). HCT was performed and analyzed according to British Thoracic Society recommendations (2011). Median (me) was shown. Pearson correlation (r) was used. P value ≤0.05 was considered significant. Results: Fifteen respiratory patients were included: 5 chronic obstructive pulmonary disease, 2 asthma, 2 pneumectomy, 2 obstructive sleep apnea and 4 other respiratory diseases. Seven patients (46.7%) had a positive HCT. Correlation between PaO2 on HCT (mmHg) (me=55.0) and FEV1 (%) (me=76.5; r=0.390, p=0.150), FEV1 (mL) (me=1485.0; r=0.503, p=0.096), FVC (%) (me=97.7; r=0.407, p=0.148), FVC (mL) (me=2465.0; r=0.559, p=0.059), DLCO (%) (me=66.9; r=0.444, p=0.097) and resting sea level PaO2 (mmHg) (me=69.0; r=0.562, p=0.072) was not significant. A positive correlation was observed between PaO2 on HCT and sea level SpO2 (%) (me=95.0; r=0.674, p=0.006). Conclusions: In this sample of respiratory patients, there is a moderate correlation between baseline SpO2 and PaO2 on HTC. LFT did not predict PaO2 on HTC. HTC remains an essential tool to evaluate if respiratory patients need in-flight oxygen.