Is air travel safe for those with lung disease?

To the Editors:

I read with interest the article of Coker et al. 1 regarding the safety of commercial air travel for patients with lung disease. This is an area of concern since both the prevalence of chronic obstructive pulmonary disease and the number of people flying for leisure purposes are increasing. The available guidelines are based on very limited scientific evidence. Owing to the lack of data and potential adverse consequences of hypoxaemia induced by air travel, the recommendations proposed by scientific societies and panel guidelines are purposefully cautious.

The prospective evaluation of a large cohort such as the one described by Coker et al. 1 is of great value for increasing knowledge in this field, and potentially for the refinement of recommendations for patients planning air travel. If patients included in the study of Coker et al. 1 were indeed managed according to guidelines, it can be concluded that these guidelines are appropriate for predicting safe air travel. It could be argued, however, that current guidelines are too restrictive or cautious. The guidelines all recommend avoidance of hypoxaemia below an arterial oxygen tension (P_a,O2) of 6.7 kPa (50 mmHg) 2–4 or 7.3 kPa (55 mmHg) 2, 5.

Bearing this in mind, it would be of great value to the scientific community to obtain the following additional information, which is probably already available to Coker et al. 1. 1) How many patients with an arterial oxygen saturation measured by pulse oximetry (S_p,O2) of 92–95% underwent hypoxic challenge testing (HCT)? 2) Did all patients with a P_a,O2 of 6.7 kPa (50 mmHg) during HCT fly with oxygen? 3) How many patients with an S_p,O2 of <92% at ground level flew without oxygen?

HCT is useful for predicting the level of hypoxaemia that patients will experience during a flight. However, it is not clear which patients should undergo HCT, i.e. which patients are at risk of an in-flight P_a,O2 of <6.7 kPa (<50 mmHg). Coker et al. 1 reported that 19 of the 82 patients who underwent hypoxic challenge testing despite a ground-level S_p,O2 of ≥96% did indeed experience severe hypoxaemia during the test. It would be interesting to characterise these patients. How do they compare to those of the same ground-level S_p,O2 but without severe hypoxaemia under hypoxic conditions? Limited data from the literature suggest that patients with very severe obstructive lung disease (forced expiratory volume in one second of <1 L 6 and/or hypercapnia 7, 8) are at risk of severe in-flight hypoxaemia despite a good ground-level S_p,O2.

Accordingly, it would also be interesting to have answers to the following questions concerning Global Initiative for Chronic Obstructive Lung Disease stage IV chronic obstructive pulmonary disease patients. 1) How many patients with a ground-level arterial oxygen saturation measured by pulse oximetry of >95% underwent hypoxic challenge testing? 2) How many patients flew without oxygen and without pre-flight hypoxic challenge testing?

Statement of interest

None declared.