Hypoxic Challenge Test (HCT) information sheet

Respiratory lab contact details

The Children's Hospital at Westmead: 

Sydney Children's Hospital, Randwick.

Introduction

A hypoxic challenge, or high altitude simulation test, is used to aid clinicians when assessing if your child will require extra oxygen while travelling on an aircraft.

About the test

  • At sea level, oxygen makes up about 21% of the air that we breathe in. However, aircraft cabins are pressurised to between 5,000 to 8,000 feet, which means that the partial pressure of oxygen inside the aircraft is lower than what we breathe at sea level (i.e. approx. 15% oxygen available during a long haul flight).
  • The hypoxic challenge test may help evaluate how well your child will tolerate the reduced oxygen levels in an aeroplane and may assist their doctor decide if your child will require extra oxygen on the flight and if they are safe to fly.
  • It is important to remember that while this test can be helpful as a guide for the doctor, there are many other factors that the doctor may consider in addition to these test results that may affect the doctor’s decision-making process. 

Preparing for the test

  • You may be asked to bring any medical equipment that your child requires e.g. suction equipment.
  • Please bring along a favourite toy, book or electronic device which can help as a distraction during the test.
  • It can get hot inside the cabin, so if you need to sit inside the cabin with your child, you and your child may wish to wear light clothing.
  • If you are accompanying your child in the cabin during the test, the scientist will ask for a brief medical history for yourself (in particular respiratory or cardiac conditions). 

On the day of the test

Step 1

The hypoxic challenge test takes place in a cabin that simulates being in an aircraft. The child/patient will need to sit inside the cabin for a set amount of time, usually 20 minutes (but in some patients, who require additional monitoring, this may be longer).

Step 2

If your child is old enough they can sit in the cabin by themselves, otherwise they may sit on the parents/guardians lap for the duration for the test.

Step 3

To monitor oxygen saturation levels and heart rate, the scientist will attach a sensor to the patient’s finger or foot. Whilst inside the cabin, babies can be bottle-fed or breast-fed as required.

Step 4

The scientist may also attach a nasal cannula to the patient’s nostril to provide oxygen if required. Once settled inside the cabin, the test will commence and the oxygen within the box will decrease.