According to the World Health Organization, the air pressure inside the cabin of a commercial aircraft at cruising altitude (36,000 to 40,000 feet) is equivalent to the outside air pressure at 6,000 to 8,000 feet above sea level. During flight, the amount of oxygen a person carries in their blood (partial pressure of oxygen, or PaO2) is reduced compared to when they are at sea level. People with healthy lungs can generally tolerate this reduced oxygen level (hypoxia), but when lung function is compromised, or other medical conditions exist, hypoxia may lead to severe hypoxemia and respiratory distress. How do you know if you are among those who need oxygen during in-flight travel? A study published in Thorax aimed to answer this question.
In-flight oxygen is generally recommended when doctor's anticipate that a patient's PaO2 will drop below 50 to 55 mg/Hg. Historically, predicting which patients will fall into this category has been difficult. Currently, doctors rely on the patient's resting oxygen saturation levels and clinical factors that would place them in a high-risk group. The hypoxia-altitude simulation test (HAST) has also been used, but it is highly sophisticated and not widely available. Other, less accurate measures are in existence, but are also known for overestimating the need for in-flight supplemental oxygen, which can also present a problem for COPD patients. A possible solution: A clinical algorithm that is more efficient in determining which patients need supplemental oxygen during air travel and which patients don't.
The algorithm was constructed based on results of the study, which consisted of 100 COPD patients, each with moderate to very severe COPD and an FEV1 of less than 80 percent. All patients underwent HAST and pulmonary function testing, along with pulse oximetry, arterial blood gases and the 6-minute walk test. Results of the tests were used to determine whether the patient was clinically fit to fly without further evaluation, whether they needed further evaluation with HAST or whether they required supplemental oxygen without the need for further testing.
Here's what the algorithm looks like:
- If a patient's resting oxygen saturation level (SpO2) is less than 92%, they should be prescribed in-flight, supplemental oxygen.
- If a patient's SpO2 is 92-95%, they should undergo a 6-minute walk test (6MWT). If, during the 6MWT, the patient's SpO2 drops below 84%, in-flight oxygen should be prescribed. If, during the 6MWT, the SpO2 is greater than, or equal to 84%, the patient should receive the high-altitude simulation test (HAST).
- If a patient's SpO2 is greater than 95%, the patient should undergo a 6MWT. If, during the 6MWT, the patient's oxygen saturation levels fall below 84%, they should undergo HAST. If the SpO2 is greater than 84% during the 6MWT, in-flight oxygen is not recommended.
Are you someone who normally doesn't require supplemental oxygen, but are wondering whether you'll need it for upcoming air travel? Because oxygen is a drug requiring a prescription, your doctor is the only one who can prescribe it to you. Although the algorithm is simple and may prove an effective tool for predicting who needs in-flight oxygen and who doesn't, it was not without limitations. Present these study results to your doctor and ask her if she recommends in-flight oxygen for your trip.
Anne Edvardsen, et. al. Chronic obstructive pulmonary disease Air travel and chronic obstructive pulmonary disease: a new algorithm for pre-flight evaluation. Thorax 2012; 67:11 964-969. Published online first: 5 July 2012 doi:10.11/thoraxjnl-2012-201855.
World Health Organization. International Travel and Health. 2013.