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Air travel can cause or worsen certain medical problems; some are considered a contraindication to flight (see Contraindications to Flying), and others may cause discomfort. Serious complications are rare.
During a flight, any health care practitioner among the passengers may be asked to help fellow passengers who become ill. Additionally, most commercial aircraft carry first-aid equipment, including an automatic external cardioverter defibrillator and limited medical supplies. Airline personnel are receiving more first-aid training now than in the past. Although physicians aiding ill or injured passengers are usually protected from litigation by the Good Samaritan concept, they should avoid practicing beyond their training or expertise.
Further information about air travel may be obtained from the medical department of major airlines, the Federal Aviation Administration ( www.faa.gov ), online travel information sources, or local travel clinics.
Contraindications to Flying
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 (see also Circadian Rhythm Sleep Disorders : Circadian rhythm sleep disorder, jet lag type (jet lag disorder)). 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. People traveling eastward could maximize exposure to bright light in the early morning to help awakening and promote earlier sleep.
Short-acting hypnotics (see 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 the elderly and should be avoided. Melatonin, a hormone secreted by the pineal gland, may provide a time-of-night cue; however, large placebo-controlled trials showing melatonin’s safety and efficacy are lacking (see Melatonin). Taking melatonin (0.5 to 5 mg po before the desired sleep time) may help those who need to go to sleep earlier because they have traveled east across several time zones. 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 a typical 8000-ft (2440-m) cabin altitude, the partial pressure of O2is about 25% less than at sea level, which, because of the O2-Hb dissociation curve (see Figure: Oxyhemoglobin dissociation curve.), represents a drop in arterial O2 saturation of only about 4.4%. This decrease may be significant for people with severe heart or lung disease (see Contraindications to Flying) but is harmless to most people; however, after 3 to 9 h 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 O2. However, problems may arise for travelers with moderate or severe pulmonary disease (eg, asthma, COPD, cystic fibrosis), heart failure, anemia with Hb < 8.5 g/dL, 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 O2 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.
Motion sickness is often triggered by turbulence and vibration and is made worse by warmth, anxiety, hunger, or overeating (see also Motion Sickness). Symptoms may include nausea, vomiting, sweating, and vertigo.
Motion sickness can be minimized before and during travel by moderating intake of food, fluids, and alcohol. Fixing the eyes on a stationary object or on the horizon can help, as can lying down and keeping the eyes closed. Other measures include choosing a seat where motion is felt least (eg, in the center of an airplane, over the wing), refraining from reading, and using an air vent. A scopolamine patch or an OTC or prescription antihistamine is often useful, especially if taken before travel. However, these drugs can cause drowsiness, dry mouth, confusion, falls, and other problems in the elderly.
Uncomplicated pregnancy through 36 wk is not a contraindication to air travel; high-risk pregnancies must be individually evaluated. Flight during the 9th mo usually requires a physician’s written approval dated within 72 h of departure and indicating expected delivery date. However, policies may vary by airline. Seat belts should be worn below the abdomen, across the hips.
To prevent effects on development of the fetal thyroid, pregnant women should avoid prolonged use of water purification tablets that contain iodine. Pregnant women should consider delaying travel to areas where malaria is endemic because malaria can be more virulent in pregnant women. Mefloquine is thought to be safe for use during all 3 trimesters of pregnancy. When traveling, pregnant women should be particularly careful about following safe food guidelines and hand washing.
Hypnosis and behavior modification benefit some people with fear of flying or claustrophobia. Fearful passengers may also benefit from a short-acting anxiolytic (eg, zolpidem, alprazolam) taken before and, depending on duration, during flight. Hyperventilation commonly simulates heart disease and may cause tetany-like symptoms; anxiety and hyperventilation can cause panic, paranoia, and a sense of impending death. Psychotic tendencies may become more acute and troublesome during flight. Patients with violent or unpredictable tendencies must be accompanied by an attendant and appropriately sedated.
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). Frequent (every 1 to 2 h) ambulation, short-movement exercises while seated, and adequate hydration are recommended; however, studies showing benefit from these measures are lacking.
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 handicaps and special needs, including those who require O2 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.
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