What is a hypoxic challenge test?

A hypoxic challenge test is used to assess whether you need extra oxygen while travelling on a plane, due to the reduced levels of oxygen in aircraft cabins.

Planes cruise at altitudes of 10,000m to 18,000m (33,000ft to 60,000ft), which is not sustainable to human life, so aircraft cabins are pressurised to levels that you can breathe at. The Civil Aviation Authority states that the ‘cabin altitude’ of commercial aircrafts should not surpass 8,000ft, and most aircrafts typically pressurise between 5,000 and 7,500ft. At 8,000ft, the fraction of inspired oxygen (FiO2) is approximately 15% compared to 21% at sea level, resulting in lower oxygen saturations for aircraft travellers.

While this is safe for most passengers, some people with pre-existing health conditions may not cope well with the lower levels of oxygen circulating in their body while on a plane. To help with this, affected passengers can have extra oxygen on the flight, but the amount of oxygen required varies from person to person.

To find out whether you need extra oxygen for a flight,  you can take a hypoxic challenge test in a medical setting before flying.

Who can benefit from hypoxic challenge testing?

Anyone with a condition that affects their blood oxygen levels, who is planning to travel by plane, can benefit from hypoxic challenge testing.

Your blood oxygen saturation level shows the percentage of oxygen in your blood, with a healthy level being between 95% and 99%. If you have breathing difficulties or medical conditions, your blood oxygen saturation levels can be much lower. Hypoxic challenge testing is best suited for people with levels below 95%, however this should be discussed with a medical professional beforehand as each case can differ.

There are several conditions that can cause your blood oxygen saturation levels to drop, including:

If you have a condition that affects your breathing and you plan to travel by plane soon, you may benefit from hypoxic challenge testing to determine if you do need to have oxygen when flying.

The test is suitable for people who have not previously had intolerance to travelling on a plane.

How is a hypoxic challenge test performed?

The first step in a hypoxic challenge test is for our lung function specialists to take a small blood sample from you. This is to establish your current blood oxygen level to compare the results of the test against.

Next, our specialists will ask you to breathe through a mouthpiece which will deliver a lower oxygen concentration, like that experienced at an altitude of 8,000ft, for approximately 20 minutes.

This allows our specialists to see how your body reacts to lower oxygen levels, while monitoring your heart rate and blood oxygen levels too. If your oxygen levels start to drop during the hypoxic challenge test, the physiologist will take a second blood sample and stop the test, providing oxygen if needed to recover.

The testing process is completely safe in a controlled medical environment, supervised closely by our lung function specialists.

How to prepare for a hypoxic challenge test

Our hypoxic challenge testing service takes place at our Wimpole Street Consulting Rooms and Diagnostic Centre.

You should allow up to 2 hours for the hypoxic challenge test, from arriving at the clinic to leaving.

Before you visit us for your hypoxic challenge test, it’s important that you let us know if you have had any hospital admissions or infections in the 8 weeks leading up to the test. This is because it can affect your breathing and blood oxygen levels, therefore impacting the results of the test.

Hypoxic challenge test results

Results of the test will be reported and sent to your consultant within 24 hours of completion. A consultant will discuss the findings with you and advise whether you will need extra oxygen for air travel.

If your hypoxic challenge test shows that you require additional oxygen, you should contact the airline you plan to travel with and let them know how much oxygen you need for the journey. You will need to speak to them about their oxygen supply policy as this can vary between airlines. Some airlines will supply the oxygen you need, while others may require you to bring your own, and there may be additional charges associated with this.

Your oxygen prescription following your hypoxic challenge test is valid for 6 months, after which you will need to visit us again for a reassessment.

Book your hypoxic challenge test

The cost of the test is £400 and it is only available privately.

To book a hypoxic challenge test at Wimpole Street Consulting Rooms and Diagnostic Centre, or for further information about the process, please get in touch with our team.

Explore our respiratory medicine specialists

Our respiratory specialists manage and treat a wide range of respiratory conditions.