In-flight PaO₂ (ABG & PFT)
This formula is taken from Dillard et al (1995) based on 33 patients with COPD and 9 healthy male controls. There were only 3 women included in the 33 patients with COPD. An alternative equation requires only an arterial blood gas measurement. It is unclear if this equation applies to patients with restrictive lung disease, however a well-validated equation for this population does not yet exist.
Most commercial aircrafts are pressurized to maintain a cabin pressure greater than that expected for the flying altitude. This pressure is typically equivalent to an altitude of less than 8000 feet. At this pressure, patients with a resting SpO2 > 95% at sea-level do not require further evaluation for in-flight oxygen. Patients with a resting SpO2 < 92% require supplemental in-flight oxygen. Those patients with an SpO2 92-95% require further assessment in the presence of pre-existing pulmonary, cardiac, or cerebrovascular disease. This assessment includes an arterial blood gas and possibly pulmonary function testing.
Patients not requiring supplemental oxygen at baseline will usually achieve adequate oxygenation with in-flight oxygen at 2 l/min via nasal cannula. In patients already requiring supplemental oxygen at sea-level, flow rates should be increased during flight. There are no specific recommendations in this situation, however the required flow rate can be determined by monitoring SpO2 with inhalation of gas containing 16% oxygen.
Airlines typically require 48 hours notice as well as documentation regarding indication, dose, and duration of oxygen therapy.
Dillard TA et al.