What Is Motion Sickness And What Causes Motion Sickness

What is Motion sickness,it is a syndrome characterized by pallor, sweating, salivation, and nausea that frequently progresses to vomiting. Prostration may be severe if exposure to precipitating factors is prolonged. It may occur in persons riding in airplanes, ships, automobiles, or trains, or sometimes in children following prolonged or vigorous sessions in playground swings. Among air travelers, the incidence has declined with introduction of newer jet transports that fly at altitudes above the layers of most tur­bulent air. The disorder still remains a problem among passengers in small aircraft and others flying at low altitudes in stormy or hot weather, when turbulence may be severe.

What Is Motion Sickness And What Causes Motion Sickness

Etiology.

Causative factors are not com­pletely understood. Labyrinthine stimulation resulting, from repetitive pitching, rolling, ro­tating, or up-and-down motion is clearly a most important factor, since persons with nonfunc­tioning labyrinths are often totally insusceptible to motion sickness, and since incidence and severity are commonly proportional to severity and duration of the motion. Psychic factors also appear to be important. Apprehension undoubted­ly predisposes to motion sickness; a few unfortu­nates feel nauseated on stepping aboard a motion­less airplane or a ship at a pier.

Some people can tolerate motion without distress until the}’ smell an unpleasant odor such as that of cigar smoke or the vomitus of a fellow passenger. Visceral sensations of motion appear to be contributory, since abdominal restraint reduces incidence of reactions. Visual stimuli apparently may play a part; symptoms sometimes occur in an immobile subject who watches moving pictures depicting motion.

Prevention and Treatment.

Prophylaxis may often be achieved by the use of any of a number of drugs, given 30 minutes to an hour before the trip begins. Hyoscine, 1.2 mg., with d-amphetamine, 20 mg., meclizine (Bonine), 25 to 50 mg., cyclizine (Marezine), 50 mg., and dimenhydrinate (Drama- mine), 50 mg., are among the most effective agents.

For prolonged journeys, the same dose of mecli­zine or hyoscine-d-amphetamine should be given every 24 hours; doses of cyclizine or dimenhydrinate should be repeated every four to six hours as required. A traveler who senses the onset of an attack may often avert nausea and vomiting by reclining as far as possible, by holding his head firmly against a pillow or head rest, by closing his eyes or fixing his gaze on a point, and by increasing his ventilation with cool air. In treatment, the same drugs mentioned above are useful, though retention may be difficult if vomiting has already occurred. Fortunately, symptoms usually dis­appear soon after the journey is concluded or motion has ceased. Recovery following prolonged vomiting may be had. ned by fluid replacement.

PROBLEMS OF AIR TRAVEL

For the normal person, and for most ambulatory patients under a physician’s care, air travel is no more trying than is travel by any other means. However, a physician should be informed of factors encountered in flight that may have an influence on his patient’s welfare. Besides accepting as passengers many ambulatory patients under the care of physicians, most airlines are prepared to carry litter patients; special litters can be accom­modated by adjustment or removal of several seats.

In remote areas, private flying agencies sometimes provide air ambulance service to large medical centers. Before a patient travels or is moved by air, the physician should consider the hazards mentioned below and should, if necessary, discuss the case with a medical official of the carrier. The patient’s condition, the altitude and duration of the flight, the cabin pressure altitude, and the availability of oxygen in flight all have a bearing on suitability of air travel by, or move­ment of, a patient. With proper precautions, all but a few patients can safely be carried by air.

Factors to be Considered. Aside from the possi­bility of motion sickness, the two most important factors to be considered in air travel by patients are reduction in air pressure and reduction in oxygen content of air at altitude. Cabin pressurization in larger and newer aircraft minimizes these changes, but hazards may be present for a few persons.

Here You Will Find Complete Guide About What Is Motion Sickness And Problems of Air Travel

In pressurized airplanes, cabin pressure is normally maintained at a fixed excess over that of the outside air. The amount of excess varies with the type of aircraft, but the differential is com­monly in the neighborhood of 8 pounds per square inch. This gives a cabin pressure that does not fall below that of sea level until the aircraft reaches 22,000 feet. Above this, internal pressure falls until at 40,000 feet the cabin has an “altitude” of 7000 feet above sea level. In older aircraft, pres­sure differentials are smaller, and cabin pressures on some flights may be equivalent to as much as 9000 feet. Only a few light aircraft are pressurized; these are often flown at 10,000 to 12,000 feet, or even more over mountainous terrain.

Hazards of Reduced Pressure.

A bubble of gas trapped within the body will expand as air pres­sure is reduced. At an altitude of 5000 feet, trapped gas expands to 125 per cent of its sea level volume, and at 10,000 feet to 150 per cent of its sea level volume. Expansion causes pressure on surrounding tissues; this may jeopardize blood supply, and may cause rupture of containing walls.

Persons with unreduced hernia should not fly, since if gas is trapped it may expand and interfere with circulation. A perforating wound of the eye­ball or the skull may allow entrance of a bubble of air that might expand at altitude. Patients with these injuries should not travel or be moved by air until absorption is complete. Patients with pneu­mothorax should not fly until all air has been absorbed. – The same caution applies following pneumoencephalography.

Expansion of abdominal gas causes some distention, and patients who have had abdominal surgery should not fly for two weeks following surgery. A patient with a colos­tomy may expect filling of the bag on ascent. Patients with acute upper respiratory tract disease may have discomfort in the sinuses or middle ear because of closure of the Ostia of the sinuses^or the eustachian tube and consequent failure of pressure adjustment during ascent or descent; use of de­congestant nose drops or inhalers before flight may avert difficulty.

A similar precaution is useful for the patient with chronic sinusitis or allergic rhinos. Patients with lung cavities, abscesses, or bulbous emphysema should not fly because of the danger of rupture.

Hazards of Reduced Oxygen.

Oxygen content of alveolar air is reduced at increasing altitudes. Though oxygen saturation of the blood is less markedly reduced, patients whose tissue oxygena­tion is marginal for any reason (whether from impaired pulmonary function, reduced oxygen carrying capacity of the blood, or impaired tissue circulation) should not fly unless prior arrange­ment has been made with the airline for oxygen to be continuously available in flight.

Patients should not fly following myocardial infarction until they are symptom-free with moderate ex­ertion, usually at least six weeks after an attack. Patients with angina pectoris that is symptomatic on climbing a flight of stairs should have supple­mental oxygen available during flight. Anemia. when the hemoglobin is less than 50 per cent, should preclude flight unless oxygen is available. A person with sickle-cell disease or sickling trait is vulnerable to haemolytic crisis and splenic in­farction with reduced oxygen tension, and should not fly without oxygen in flight.

Patients with developing gangrene or carbon monoxide poison­ing should not be moved without supplemental oxygen in flight. Any pulmonary disease, when severe enough to cause cyanotic at ground level, to seriously impair exercise tolerance, or to reduce vital capacity below 50 per cent of normal, is a contradiction to flight unless supplemental oxygen is made available.

Aerial movement is sometimes considered for a patient who has recently suffered from an attack of poliomyelitis. In general, such a patient should not be moved by air until his condition has become stabilized. If respiratory paralysis has occurred, the patient who is able to be out of a respirator for 8 to 12 hours a day can usually be moved safely by air.

For those requiring a respirator continuously, portable equipment is available that can be carried in aircraft. Such patients should be observed carefully in flight by an experienced attendant, with special attention to the main­tenance of normal ventilators exchange and the avoidance of dehydration, as this tends to make secretions thicker and more difficult to aspirate. If bulbar involvement has caused difficulty in swallowing, a tracheostomy should be performed prior to flight to ensure adequacy of the airway.

Time Zone Changes

Subjective fatigue and de­lays in adjustment to time zone changes following east-west or west-east travel are matters of com­mon observation. Not only sleeping habits, but more profound cycles of deep body temperature, water and electrolyte excretion, plasma lactic dehydrogenase, and other physiologic measures are involved. The time required for a traveler to “get on schedule” at the destination depends upon many factors, including individual characteristics, the number of time zones passed, the opportun­ities for rest before and after flight, and, for some, the direction of flight.

A traveler to the west is not likely to have trouble in going to sleep at night in the new time zone, but he may have morning insomnia; one traveling several time zones to the east is likely to experience evening insomnia and retarded awakening. If the traveler has a tend­ency toward insomnia, travel may cause a trouble­some accentuation.

Studies have indicated some actual impairment of psychologic performance in the 24 hours im­mediately following travel through 7 to 12 time zones.

Performance has commonly returned to normal following one good night’s sleep. Adjust­ment of sleeping habits and the overcoming of subjective fatigue may take several days; the deeper physiologic cycles require longer periods — from four to eight days for adjustment to a time differential of 7 to 12 zones.

Travelers can minimize problems by giving special attention to rest before and after long flights. If circumstances permit before the trip, the prospective traveler may benefit from modify­ing his sleep schedules toward those of the desti­nation. Trusted omniscient for a few nights after arrival’ may speed the adjustment. Some experienced travelers recommend that “million dollar decisions” be avoided in the first 24 hours after a long flight.

Other Hazards.

Prolonged sitting and inac­tivity may be hazardous for persons with a history of thrombophlebitis or other circulatory disorder of the lower extremities. These patients should be advised to move about frequently during long flights. A patient with a fractured jaw treated by fixation should not fly because of the danger of aspirating vomits in case of motion sickness. If he must fly, a quick-release fixation should be devised.

Common Questions.

Physicians are often asked questions about flying. Normal infants tolerate air travel well, but feeding should be given during descent, to facilitate aeration of the middle ear by swallowing. Old age in itself is no contrain­dication to flight, if significant disease is not pres­ent. Pregnancy is no contradiction to flight, but if the mother is near term, the airline may require a physician’s statement that delivery is not likely to occur during the flight. There is no evidence that the mild oxygen deficit in the atmosphere is harmful to the fetus. Hypertension is not adversely affected by air travel, though preflight sedation may be appropriate.

Patients with communicable diseases should, of course, not travel when hazards of transmission to others exist. Patients whose conditions make them objectionable to others, such as those with urinary incontinence or malodorous discharges, should not travel in the crowded cabins of commercial aircraft. Mild asthma is not ordi­narily adversely affected by flight. Patients sub­ject to severe asthmatic attacks should carry their tested medications, and should ensure in advance the availability of oxygen if needed. In epileptics, oxygen deficiency and hyperventilation attending excitement in flight may precipitate seizures.

Persons subject to frequent seizures should have proper medication, including sedation, prior to travel by air and if possible should be accompanied by an attendant. Psychiatric disorders require in­dividual evaluation; the likelihood of disturbance or agitation under the minimal stress of travel and the safety and comfort of fellow passengers should be considered. Questions regarding other condi­tions should be referred to the airline’s nearest medical official. Indeed, it is advisable to discuss with the airline’s medical official any prospective passenger whose condition might be unfavorably influenced by flight.

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