First, We assess his Oxygen Saturation at Sea level.

• Patients who can maintain oxygen saturation of 95 % or more at sea level:
  • No need for supplementary oxygen during the flight
• Patients with Oxygen saturation at sea level between 92-95% and no other risk factors:
  • No need for supplementary oxygen during the flight
• Patients with oxygen saturation at sea level between 92-95% and other risk factors:
  • Perform hypoxic challenge test
• Patients with Oxygen saturation at sea level less than 92%:
  • Advise in-flight supplementary oxygen

How do we perform a Hypoxic challenge test?

• Keep the patient at FiO2 (fraction of inhaled oxygen) of 15 percent for 15 minutes
• Perform arterial blood gases after 15 minutes:
  • If the patient has a paO2 of more than 55 mmHg: No supplementary oxygen is required
  • If the paO2 is between 50 to 55mmHg: Consider oxygen therapy
  • If the paO2 is less than 50 mmHg: Advise in-flight Oxygen @ 2litres/min.

Normal air has 21% Oxygen. This means that the lowest FiO2 we can use during the test is 21% (or 0.21). How can we perform the test at FiO2 of 15%?

Are there special low oxygen chambers where the test can be done? 

The cut-offs for the test are given at sea levels. How can we do it in our hospital settings as we are at a height about 500 meters above sea level?