Air travel has become increasingly popular over time, despite decreases during the COVID-19 pandemic, with 1.1 billion total passengers in 2019 and most Americans having flown at least once in the past three years.¹ Air travel is generally safe, but especially for the aging U.S. population, the flight environment poses unique physiologic challenges, particularly relative hypoxia, which may trigger adverse myocardial or pulmonary outcomes. To optimize health outcomes, communication must take place between the traveler, family physician, and airline carrier when any doubt occurs about fitness for air travel. Travelers should carry current medications in their original containers as well as a list of their medical conditions and allergies and should adjust timing of medications as needed based on time zone changes. Travelers should also consider available medical resources at their travel destinations and layover locations. Family physicians and travelers can review relevant pretravel health information, including required and recommended immunizations, health concerns, and other travel resources appropriate for any destination worldwide at https://wwwnc.cdc.gov/travel/destinations/list.

Pulmonary Conditions

By law, U.S. commercial aircraft cannot exceed a relative cabin altitude of 8,000 feet (2,438 m) because of the potential for significant hypoxia above this altitude.² Most passengers exposed to this environment will have a partial pressure of arterial oxygen (Pao₂) of 60 to 65 mm Hg (7.98 to 8.64 kPa), corresponding to 89% to 94% peripheral oxygen saturation (Spo₂), which may compromise cardiovascular or pulmonary disease in affected travelers.³ Neither reassuring pulse oximetry nor reassuring forced expiratory volume in one second has been found to predict hypoxemia or in-flight events for patients with pulmonary conditions.³

The nonstandardized Hypoxia Altitude Simulation Test, administered and interpreted by pulmonologists, can be used to determine specific in-flight oxygen requirements for patients with pulmonary complications or those for whom safe air travel remains in doubt. Typically, the Hypoxia Altitude Simulation Test comprises breathing 15% fraction of inspired oxygen for 20 minutes, with pulse oximeter and blood gas measurements taken before and after testing.^4–6 Patients with a Hypoxia Altitude Simulation Test Pao₂ less than 50 mm Hg (6.65 kPa) at any point during the test require supplemental oxygen in flight, whereas those with a Pao₂ greater than 55 mm Hg (7.32 kPa) do not. Pao₂ measurements falling between 50 and 55 mm Hg are considered borderline and may necessitate further testing with activity.⁵ Given that the test itself incurs some risk and may not be available to all travelers, family physicians can counsel patients who are unable to walk 50 m (164 ft) or those whose usual oxygen requirements exceed 4 L per minute not to fly.^3,4,7,8

Patients with oxygen requirements less than 4 L per minute can be counseled to double their usual flow rate while flying.⁸

Commercial airline carriers usually permit the use of personal Federal Aviation Administration–approved portable oxygen compressors, but carriers require travelers to give from 48 hours to one month's notice before flight when they are requesting the use of compressed oxygen.⁹

Table 1 lists indications for which further assessment (e.g., Hypoxia Altitude Simulation Test, ability to walk 50 m) is warranted, including previous respiratory difficulties while flying, severe lung disease, recent or active lung infections, any preexisting oxygen requirements or ventilatory support, or if less than six weeks have passed since hospital discharge for acute respiratory illness.³ Patients who have undergone an open-chest lung procedure should defer travel for two to three weeks, must not have any recent or residual pneumothorax, and should be assessed for supplemental oxygen needs.¹⁰

Cardiac Conditions

Travelers with underlying cardiac conditions should use airport assistance services such as wheelchairs and baggage trolleys to decrease myocardial oxygen demand.⁹ Although most cardiac conditions are safe for flight, some require additional consideration. Travelers with minimally symptomatic, stable heart failure may safely fly, but medication adherence is critical.^9,11 Patients with stable angina should be assessed for oxygen needs if they become short of breath after walking 50 m, and they should not fly following any recent medication changes that have not demonstrated clinical stability beyond that medication's half-life.^7,11