Fit to fly
Intermittent Hypoxic Training and Cardiorespiratory Assessment for Air Travel
Intermittent Hypoxic Training (IHT) is a technique that involves breathing air with a reduced oxygen concentration for short, repeated intervals, alternating with periods of breathing normal air.1 This method is being explored as a non-invasive tool to assess how people with cardiorespiratory conditions, such as chronic obstructive pulmonary disease (COPD) or congestive heart failure, might tolerate the low-oxygen environment of an airplane cabin.
Why IHT Is Used
The primary purpose of using IHT is to simulate the hypobaric hypoxia experienced during air travel. At a typical cruising altitude of 30,000 to 40,000 feet, the air pressure inside a commercial airplane cabin is maintained at an equivalent altitude of 5,000 to 8,000 feet. This reduced pressure leads to a decrease in the partial pressure of oxygen, which can cause blood oxygen saturation levels to drop. For healthy individuals, this is usually not a problem, but for those with pre-existing cardiorespiratory issues, this drop can exacerbate their symptoms and lead to serious health complications.2
How IHT Is Performed
The IHT assessment typically involves the patient inhaling a hypoxic gas mixture (usually 12-15% oxygen) for a few minutes, followed by a return to breathing ambient air (around 21% oxygen). During this process, key physiological parameters are monitored, including:
- Arterial oxygen saturation (SpO2): Measured using a pulse oximeter. A significant or rapid drop is a key indicator of poor tolerance.
- Heart rate (HR): An excessive increase may indicate cardiovascular strain.
- Respiratory rate (RR): An increase suggests the body is working harder to compensate for the lack of oxygen.
- Blood pressure (BP): Monitored to detect any dangerous fluctuations.
Interpreting the Results
Based on the physiological response to the IHT session, a healthcare professional can determine if a patient is “fit to fly.” If a person’s oxygen saturation remains stable and they don’t experience significant changes in heart rate or breathing, they are generally considered at low risk. However, if their oxygen saturation drops below a certain threshold (e.g., 85-90%) or they develop severe symptoms like shortness of breath, chest pain, or dizziness, they may be deemed unfit to travel without supplemental oxygen.5 In such cases, the IHT assessment provides objective data to support the prescription of in-flight oxygen, ensuring the patient’s safety.
Cottrell, L., et al. (2010). Flight assessment in patients with respiratory disease: hypoxic challenge testing vs. predictive equations. QJM: An International Journal of Medicine, 103(6), 361-366.
Robson, A. G., & Innes, J. A. (2006). Problems of air travel for patients with lung disease: clinical criteria and regulations. Breathe, 3(2), 140-149.
