Long-haul flights may induce respiratory changes similar to ventilatory acclimatisation to altitude.

Ventilatory acclimatisation to altitude is associated with a progressive increase in ventilation, a progressive decrease in end-tidal PCO2 (PETCO2)1 and a progressive increase in the acute ventilatory sensitivity to hypoxia (AHVR)2. The duration and severity of hypoxia generally associated with these changes are both substantially greater than those associated with commercial airline flight. Nevertheless, commercial airline flight normally involves some reduction in cabin pressure, and this study sought to determine whether the associated reduction in inspired PO2 could also induce acclimatisation.