Air Travel

Commercial airplanes and jet aircraft are pressurized only to the equivalent of an altitude of 6000 to 8000 ft (1830 to 2440 m), not to sea level pressure. Thus, air in body cavities or other closed spaces expands by about 25%; this expansion may aggravate certain medical conditions.

Untreated dental problems or recent dental procedures may become painful when air pressure changes. People with upper respiratory inflammation or allergic rhinitis may develop obstructed eustachian tubes (which may cause barotitis media) or obstructed sinus ostia (which may cause barosinusitis). Frequent yawning or closed-nose swallowing during descent, use of decongestant nasal sprays, or use of antihistamines before or during flight often prevents or relieves these conditions. Some people suck on hard candies during descent.

Air travel is contraindicated for patients who have or are likely to develop pneumothorax (eg, those who have large pulmonary blebs or cavities) and for those in whom air or gas is trapped (eg, those who have an incarcerated bowel, those traveling < 10 days after chest or abdominal surgery, those who have intraocular gas injection) because even modest expansion may cause pain or tissue damage.

Water should be substituted for air in devices secured by air-filled cuffs or balloons (eg, feeding tubes, urinary catheters). Patients with a colostomy should wear a large bag and expect frequent filling due to expansion of intestinal gas.

Children are particularly susceptible to barotitis media and should be given fluids or food during descent to encourage swallowing, which can equalize pressures. Infants can be breastfed or given a bottle or pacifier. Precautions for children with chronic disease (eg, congenital heart disease, chronic lung disease, anemia) are the same as those for adults.

Rapid travel across multiple time zones disrupts the normal circadian rhythm. Bright sunlight resets the internal clock. Exposure to bright late-afternoon or evening light delays the onset of normal sleep time, and exposure to early-morning light advances the biologic clock, so that sleep time is earlier than usual. Thus, managing exposure to light can help adaptation, particularly on the days after arrival in a new time zone. For example, people traveling westward could maximize exposure to bright afternoon light to help delay sleep time; those traveling eastward could maximize exposure to bright light in the early morning to help awakening and promote earlier sleep, for 3 to 4 days after arrival.

Short-acting hypnotics (see table Oral Hypnotics in Common Use) may help people fall asleep at the appropriate local time after eastward travel. However, hypnotics may have adverse effects, such as daytime drowsiness, amnesia, and nighttime insomnia. Long-acting hypnotics increase the likelihood of confusion and falls among older people and should be avoided.

Some therapeutic regimens must be altered to compensate for circadian dysrhythmia. For example, insulin dosage and timing may require modification depending on the number of time zones traversed, time spent at destination, available food, and activity; glucose must be monitored frequently. Target plasma glucose levels should be increased; because so many changes affect levels, tight control is more difficult, and the risk of hypoglycemia is increased. Regimens may require modification based on elapsed rather than local time.

In passenger jets at cruising altitude, with aircraft cabins typically pressurized to 6,000 to 8,000 feet (1830 to 2440-m) above sea level, the partial pressure of oxygen is about 25% less than at sea level, which, because of the oxygen-hemoglobin dissociation curve (see figure Oxyhemoglobin dissociation curve), represents a drop in arterial oxygen saturation of only about 4.4%. This decrease may be significant for people with severe heart or lung disease (see table Contraindications to Flying) but is harmless to most people; however, after 3 to 9 hours at that altitude equivalent, some people report discomfort (eg, headache, malaise).

In general, anyone who can walk 50 m or climb one flight of stairs and whose disease is stable can tolerate normal passenger jet cabin conditions without additional oxygen. However, problems may arise for travelers with moderate or severe pulmonary disease (eg, asthma, COPD [chronic obstructive pulmonary disease], cystic fibrosis), heart failure, anemia with Hb < 8.5 g/dL (85 g/L), severe angina pectoris, sickle cell disease (but not trait), and some congenital heart diseases. When flying is essential, such patients can usually fly safely with specially designed continuous oxygen equipment, which must be provided by the airline. Mild ankle edema due to venous stasis commonly develops during long flights and should not be confused with heart failure.

Smoking can aggravate mild hypoxia and should be avoided before flying. Hypoxia and fatigue may increase the effects of alcohol.

Dehydration may develop because of very low cabin humidity. It can be avoided with adequate fluid intake and alcohol avoidance. Contact lens wearers and people with dry eyes

Motion sickness is often triggered by turbulence and vibration and is made worse by warmth, anxiety, hunger, or overeating. Symptoms may include nausea, vomiting, sweating, and vertigo.

Uncomplicated pregnancy through 36 weeks is not a contraindication to air travel; high-risk pregnancies must be individually evaluated. Flight during the 9th month may require a physician’s written approval dated within 72 hours of departure and indicating expected delivery date. However, policies vary by airline. Seat belts should be worn below the abdomen, across the hips.

Malaria Prevention). When traveling, pregnant women should be particularly careful about following safe food guidelines and hand washing. On long flights, frequent ambulation is recommended to prevent venous thromboembolism (see also Restricted mobility).

Pregnant women and people planning pregnancies in the near future should not travel to areas with risk of Zika infection.

Hypnosis

Deep venous thrombosis may develop in anyone sitting for long periods and may result in a pulmonary embolus. Risk factors include those for non–altitude-related deep venous thrombosis (eg, prior deep venous thrombosis, pregnancy, use of oral contraceptives—see table Risk Factors for Venous Thrombosis

Turbulence may cause motion sickness or injury. While seated, passengers should keep their seat belts fastened at all times.

Travelers with certain medical conditions or risks should carry appropriate documentation, drugs, and devices.

• Travelers with known medical conditions should carry a medical record summary (including electrocardiography [ECG] for those with significant cardiac history).

• Travelers subject to disabling illness (eg, epilepsy) or those with chronic disease should wear a medical identification bracelet or necklace.

• Travelers with known histories of specific recurring conditions (eg, urinary tract infections, vaginal candidal infections, migraine headaches) should consider traveling with self-treatment drugs.

• Travelers who need to carry opioids, syringes, or large amounts of drugs should have a prescription or verifying letter from a physician to avoid possible security or customs complications.

The following should be packed in a carry-on bag in case checked baggage is delayed, lost, or stolen:

• Drugs, in original labeled containers

• Extra eyeglasses or other corrective lenses (as well as a current written prescription for either)

• Hearing aid batteries

The US Transportation Safety Administration (TSA) forbids carrying containers with > 90 mL of liquid or gel on a commercial flight, but the TSA allows larger amounts of medically necessary liquids, gels, and aerosols in reasonable quantities for the trip. These items must be declared to TSA officers at the checkpoint for inspection (see TSA: Disabilities and Medical Conditions).

Most implanted cardiac devices, including pacemakers and cardioverter defibrillators, are effectively shielded from interference from security devices. However, the metal content of some of these devices, as well as certain orthopedic prostheses and braces, may trigger a security alarm. A physician’s letter should be carried to avoid security difficulties.

People with specific dietary and medical needs should plan carefully and carry their own food and supplies. With several days’ notice, all airlines departing from or arriving in the US (and most others) can make reasonable efforts to accommodate passengers with physical disabilities and special needs, including those who require oxygen therapy. Wheelchairs can be accommodated on all US airlines and most foreign ones, but advance notice is advisable.

Some airlines accept passengers requiring more highly specialized equipment (eg, IV fluids, respirators) provided that appropriate personnel accompany the passenger and arrangements have been made in advance. If travelers cannot be accommodated on a commercial aircraft because of severe illness, air ambulance service is necessary.

Fair-skinned travelers are more vulnerable to sunburn at tropical latitudes and at high altitude. Use of high-SPF (sun protection factor of 30 or higher) sunscreen is advisable. When both sunscreen and insect repellent are used, sunscreen should be applied first, then, after at least fifteen minutes, insect repellent.