Clinical assessment and tests

Clinical assessment

Clinical assessment to determine the need for in-flight oxygen therapy includes cardiorespiratory history and examination, spirometry, pulse oximetry and review of previous air travel experience.

Hypoxic challenge test

The hypoxic challenge test (also known as the high-altitude simulation test) is used to assess the need for in-flight oxygen. Consider a hypoxic challenge test in patients with SpO₂ less than 95%.

The hypoxic challenge test simulates the cabin pressure by exposing the person to the reduced inspired oxygen partial pressure (PiO₂) at 2438 metres (8000 feet). The test is performed in a specialist respiratory laboratory over a 20- to 30-minute period, either with special low-oxygen gas cylinders or with the person breathing air while wearing a 40% Venturi mask with 100% nitrogen as the driving gas.

In-flight oxygen is usually indicated if SpO₂ falls below 85% or if the patient becomes distressed during the hypoxic challenge test.

Walk test

Walk tests are only recommended if hypoxic challenge testing is unavailable. However, some airlines still include the 50 metre walk test in their medical clearance form.

Patients unable to walk 50 metres on level ground should be considered unfit to fly.