Articles
Hypoxia During Air Travel in Adults With Pulmonary Disease

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ABSTRACT

At the present time, commercial aircraft cabins are required to be pressurized to the equivalent of 8,000 feet or less. Although in-flight medical emergencies are infrequent, some adults with pulmonary disease may experience significant physiological stress, exacerbation of their underlying illness, and severe hypoxemia during air travel. A careful preflight medical evaluation is essential to determine which patients with pulmonary disease can fly safely, which patients require supplemental oxygen, and which patients should not fly at all. All adults with pulmonary disease who have a preflight arterial oxygen tension of less than 70 mm Hg or a preflight pulse oximetry saturation of less than 92% should receive supplemental oxygen during air travel. The hypoxia altitude simulation test and the 6-minute walk test are useful when additional evaluation for supplemental in-flight oxygen is needed. Patients with an unstable condition, an acute exacerbation of their pulmonary disease, severe pulmonary hypertension (Class III and Class IV), or an active pneumothorax should not fly.

Section snippets

The Physiological Stresses of Air Travel

As an aircraft ascends to progressively higher altitudes, the air density of the atmosphere decreases exponentially. This, in turn, results in an exponential decrease in both barometric pressure and the partial pressure of atmospheric oxygen (PiO2).28 Most commercial aircraft fly at cruising altitudes between 25,000 and 45,000 feet. To maintain PiO2 and the partial pressure of arterial oxygen (PaO2) at safe levels during flight, commercial aircraft cabins are pressurized.29., 30.

There are

The Preflight Medical Evaluation

The utility of a careful preflight medical evaluation for individuals with cardiopulmonary disorders has been demonstrated in several studies.43., 48., 49. The Aerospace Medical Association and the British Thoracic Society have published comprehensive guidelines for the evaluation and management of individuals before air travel.1., 2. Although there are some differences in these guidelines, they both address the importance of a preflight medical evaluation, the estimation of in-flight PaO2,

The Baseline Medical Evaluation

All individuals with pulmonary disease should have a thorough history and physical examination, as well as the following studies, before air travel: spirometry, arterial blood gasses, SpO2, electrocardiogram for the detection of ischemic changes and dysrhythmias and the measurement of hemoglobin concentration. Patients with chronic obstructive lung disease (COPD) should have maximum voluntary ventilation (MVV) measured in conjunction with spirometry, if not routinely performed. Individuals with

Fifty-Yard and 6-Minute Walk Tests

A 50-yard walk test or 6-minute walk test can be very helpful in the evaluation of some patients with pulmonary disease.1., 2. Although neither has been validated in controlled studies for the preflight evaluation of patients with pulmonary disease, it is generally believed that the ability to increase minute ventilation and cardiac output in response to exercise is a simple, reliable and practical way of assessing the cardiopulmonary reserve that such patients will need to meet the

Evaluation of Preflight PaO2 and SpO2

It is currently recommended that individuals maintain an in-flight PaO2 of 50 mm Hg or greater during air travel.1., 2., 54. The single best predictor of the in-flight PaO2 is the baseline PaO2 at ground altitude.1 A stable, preflight ground PaO2 of 70 mm Hg or greater is generally considered adequate to achieve a PaO2 of 50 mm Hg or greater at an altitude of 8,000 feet, which is the maximum permissible cabin altitude for commercial aircraft.1., 2., 54., 55. It is recommended that individuals who

HAST

Breathing a hypoxic gas mixture of 15.1% oxygen at sea level will simulate breathing air with a PiO2 of 108 mm Hg at the maximum allowable aircraft cabin altitude of 8,000 feet. This is the basis for the hypoxia altitude simulation test (HAST), which was first described by Gong et al12 in 1984.

The HAST is conducted by breathing a hypoxic gas mixture of 15.1% oxygen, balanced with nitrogen, through a tight-fitting face mask or mouthpiece for 20 minutes. Arterial blood gasses are obtained before

Anemia

All patients with pulmonary disease should have the blood hemoglobin concentration measured as part of the preflight medical evaluation. Any such patient with a blood hemoglobin concentration below 8.5 g/dL should be considered for in-flight supplemental oxygen, even if no other indications are present. At such low concentrations of hemoglobin the oxygen-carrying capacity of blood is significantly diminished. Patients with pulmonary disease who have a blood hemoglobin concentration of less than

COPD

Individuals with COPD are especially susceptible to respiratory decompensation and severe hypoxemia during commercial air travel.10., 11., 14., 16., 44., 46., 47., 54., 56. Their ability to increase minute ventilation in response to hypoxia is limited, even with appropriate therapy. This, coupled with underlying ventilation-perfusion mismatching, makes it difficult for some individuals with COPD to maintain adequate oxygenation during flight. It has been demonstrated that the PaO2 and SpO2 of

Asthma

Asthma is the most common respiratory disorder among commercial air travelers.1 In general, patients with stable asthma that is well controlled with medication can fly safely. It is recommended that physicians counsel asthma patients on the necessity of continuing all medication as prescribed during air travel and the importance of carrying enough medication with them to last for the duration of the trip. It is also recommended that they carry a short-acting inhaled bronchodilator and a course

Restrictive and Interstitial Lung Disease

Two studies have shown that patients with restrictive and interstitial lung diseases may be at high risk of developing a resting PaO2 below the recommended lower limit of 50 mm Hg at a simulated cabin altitude of 8,000 feet. These studies also showed that mild exercise at 8,000 feet may cause a further decline in PaO2 to a very low level.47., 62. Thus, all patients with restrictive or interstitial lung disease should be advised to refrain from exercise during air travel. Diffusion abnormalities,

Pulmonary Hypertension

Patients with pulmonary hypertension, either primary or secondary, are at high risk for complications during commercial air travel. Given the considerable individual variability in hypoxia-induced pulmonary vasoconstriction, even a mild increase in hypoxia during flight may cause very high pulmonary artery pressure and pulmonary vascular resistance in some patients. These changes could potentially cause a life-threatening decrease in cardiac output and right heart failure during flight.16., 39.

Pneumothorax

Boyle’s Law states that the volume of gas in a closed space is inversely proportional to the pressure of the gas. Therefore, as the barometric pressure of air in an aircraft cabin falls with ascent to cruising altitude, the volume of air in body cavities will expand. In noncommunicating body cavities, such as a closed pneumothorax, there is no way for the expanding gas to escape and equilibrate with the external environment. Thus, the volume of air in a closed pneumothorax will continue to

Airline-Provided Oxygen

The logistics of providing supplemental oxygen during air travel can be challenging for both the patient and physician. Patients are not permitted to carry their own compressed gas oxygen cylinders aboard commercial aircraft. However, most airlines will provide supplemental oxygen to passengers with an oxygen prescription from their physician. Each airline has its own policy for providing supplemental oxygen and there is usually a fee charged for this service. The number of oxygen cylinders

Portable Oxygen Concentrators

In 2005, the United States Federal Aviation Administration (FAA) issued a new rule which made it easier for individuals who require supplemental oxygen to fly on commercial aircraft.69 This rule allows, but does not require, airlines to permit individuals to carry FAA-approved portable oxygen concentrators with them aboard commercial aircraft and to use them during flight. At the present time there are 5 portable oxygen concentrator devices that have been approved by the FAA for use during

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