Essays & Articles

Aircrew Sleep : Civil & Military Operations
by
Wg Cdr JK Shrivastava
Cl Spl (Av Med)
Air India.

INTRODUCTION
Air crew sleep is extremely significant in the current scenario of civil & military operations. With the given speed & range of current aircraft operations, lack of rest is becoming a limiting factor in aircraft operations. Modern commercial aircrafts cross time zones at almost the same rate as the earth rotates, and it is these swift transmeridian transitions that lead to the syndrome commonly referred to as Jet Lag or Rapid Time Zone Change Syndrome. On arrival at their destination, individuals find themselves out of synchrony with the social and time cues of their new surroundings. More than 80 million people travel on transmeridian routes annually & experience Jet Lag

It is usually associated with excessive daytime sleepiness; sleep onset insomnia & frequent arousals from sleep, particularly in the latter half of the night. Gastro-intestinal discomfort is common. The syndrome is transitory, typically lasting 2 - 14 days, depending on the number of time zones crossed and direction of travel, traveller's age & the phase shifting capacity.

CIVIL OPERATIONS

WHO GETS JET LAG?
Almost everyone on a long flight suffers jet lag to some degree. A 1994 survey of New Zealand based international flight attendants showed a similar result, with 96% of respondents saying they suffered from jet lag despite being accustomed to long haul travel. Specifically 90% suffered from tiredness after arrival, 94% experienced loss of energy and motivation and 93% reported broken sleep after arrival1. It affects the passengers even more than the flight professionals. Firstly, because they are generally less accustomed to the factors causing jet lag and secondly, because they are confined to a cramped space for long periods. Young children often seem immune. People who by and large stick to a rigid daily routine and are bothered by changes in routine, are often the worst sufferers. People typically involved in highly varied routine / life styles, can often adjust their circadian rhythms better and adapt to a disruption of normal eating and sleeping patterns. People who sleep easily can also cope better with the mal - adjustment. The length of the flight is not the critical issue; the most important single factor is how many time zones are crossed.

WHAT IS JET LAG?
Jet Lag is a result of dissociation between the environmental time cues, which have been phase advanced or phase delayed and the internal clock. In addition the endogenous circadian rhythm becomes disorganized. Flight related stress and sleep loss further compound the Jet Lag Syndrome2. The syndrome is particularly more obvious after an Eastbound flight. The major manifestations of Jet Lag are as under

(a) Fatigue. Feeling of being worn out and tired for days after arriving, generally accompanied by a lack of concentration and motivation especially for any activity that requires effort or skill such as driving, reading or discussing a business deal. But, even simple daily activities can become harder, and one's capacity to truly enjoy a tourist holiday is significantly reduced.

(b) Disorientation. Especially in relation to time, location & direction.

(c) Irrational Or Unreasonable Behaviour. "Rage Behaviour", is seen in many passengers, in very tedious long haul flights especially near the end. Going through customs, immigration and getting to the hotel often seem like a real drama.

(d) Broken Sleep. Crossing time zones can cause wakefulness during the night and tendency to fall asleep during the day. Inbuilt circadian rhythms are disturbed, and it can take many days for the body to readjust to the new time zone.

(e) The syndrome is made worse by some common physical problems caused by being confined in an airliner for hours e.g.

  • Dehydration This can cause headache, dry skin, nasal irritation, and increase susceptibility to cold, cough, sore throat and flu.
  • Discomfort of Legs and Feet Limbs swelling while flying can be extremely uncomfortable, and in some cases may prevent travellers wearing their normal shoes for up to 24 hours after arrival.

(f) Infection : Factors such as travel fatigue, jet lag, a change in diet, a different climate and a low level of immunity may aggravate the problem by reducing a travellers' resistance and making them more susceptible to viral infections or mild symptoms of food poisoning.

WHAT CAUSES JET LAG?
The major known causes of Jet Lag are elaborated as under

  • Crossing Time Zones. Crossing the time zones is the principle cause of jet lag. It in noticed that Eastward flying is more problematic than Westward flying. Interestingly, children under the age of three don't suffer from the syndrome badly, as they aremore adaptive and less set in their ways. Whereas, adults who adjust readily to the changes of routine are less susceptible to the problems of jet lag. Those who are slaves to a fixed daily routine are often the worst sufferers.


  • Pre-Flight Condition. Over-tired, excited, stressed, nervous, or hungover, travellers before the flight, are more susceptible to jet lag


  • Dry Atmosphere. The air aboard passenger jet aircraft is dry. To people who normally live in more humid conditions the change can be striking.


  • Cabin Pressure. At a cruising altitude of near 30,000' the aircraft is pressurized to 8,000'. Unless acclimatized to this low pressure environment individuals may suffer from tiredness and lethargy.


  • Alcohol. The impact of alcohol on the body is 2-3 times more potent when flying. One glass of wine in-flight has the effect of 2-3 glasses on the ground.


  • Lack of Physical activities. Lack of Physical activity is one of the worst aspects of long-haul flying. It makes the flight uncomfortable and predisposes to jet lag.


  • Exposure to Light. Travelers who spend more time outdoors adapt more quickly than those who remain in hotel rooms, perhaps due to bright, outdoor light exposure.


AVOIDING JET LAG
Certain non-pharmacological methods are empirically used to avoid Jet Lag or reduce its severity.

  • Pre-flight Preparation. This is one of the most important aspects of combating jet lag. Ensure a good night's rest & avoid stress, excitement or worry, and fatigue from a function the night before. Get plenty of exercise in the days prior to departure and try to avoid sickness such as flu, colds and so on.


  • East or West. There is much debate about whether it is better to fly eastward or westward. It may be largely a matter of personal preference, but there is some evidence that flying westwards causes less jet lag than flying eastwards. Long distance flights with rapid time zone shifts of more than 3 hours lead to a dissociation of the inner circadian clock to the outer pacer. Additionally, the different endogenous circadian rhythms will no longer be synchronized with the endogenous pacer 'melatonin' leading to jet lag. Since the inner circadian rhythm extends from 24 up to 26 hours, travelling to the west with a prolongation of the daylight will be tolerated better than flights to the east with a shortening of the day length


  • Night or Day Flight. Though it is a matter of personal preference, it is experienced by the travellers that day time flights are better than the night time flight. This may be due to excessive fatigue caused by the late night flight


  • Drinking Fluids. The dry air in aircraft causes dehydration. Drinking plenty of non-alcoholic fluids counters this. Water is better than coffee, tea and fruit juices. Alcohol not only is useless in combating dehydration, but also has a markedly greater intoxicating effect when drunk in the rarefied atmosphere of an airliner than it does at ground level.


  • Sleeping Aids. Blindfolds, earplugs, neck rests and blow-up pillows are all useful in helping to get quality sleep while flying.

DRUG THERAPY FOR JET LAG
The two main principles of pharmacological treatment for Jet Lag are the promotion of sleep with hypnotics & the resynchronization of the internal body clock. The latter is achieved by timed administration of Melatonin

Melatonin. It is a hormone secreted form the pineal gland and circulated in the blood of human being and other species, has a distinct diurnal variation in its biosynthesis and, therefore, in its concentration. Melatonin is manufactured in the human body from the aminoacid Tryptophan. In humans, plasma levels are high at night & low in daytime 3 . This variation has suggested, the possibility of a regulatory function in day / night-dependent physiological processes such as sleep this has led scientists to explore the effects of administered melatonin on the modulation of circadian rhythms. Melatonin delays the circadian rhythms when administered in the morning & advances them when given in the late afternoon / evening. Melatonin also acts as a mild hypnotic. It is administered to the passengers after reaching their destination, normally at bedtime to improve sleep quality and to decrease the time required to re-establish time normal circadian rhythm. However, for those international aircrews that travel through multiple time zones without time to adapt to new environments, taking melatonin before arriving home may further impair already disturbed circadian rhythms. Melatonin is usually reserved for passengers intending to stay for longer durations at the location.

Zolpidem. Zolpidem is an imidazopyridine, structurally unrelated to the benzodizapines, has a short half-life, rapid absorption & a strong hypnotic effect with weak anti - convulsant & muscle relaxant properties. Classically, Zolpidem is indicated for short & fast acting resynchronization of the circadian rhythms e.g. cockpit & cabin crew in commercial airlines on short layovers at intermediate stations. It has minimal next-day effects ("hangover") when given at recommended doses. This factor is important for cockpit crews, who have to be mentally alert the next day, to operate the flight.

Melatonin - Zolpidem combination is poorly tolerated subjectively perhaps because of the "hangover" effect due to the additive hypnotic effect of the drugs4. There are no fixed drug regimes or measures to treat Jet Lag - combating is more of a personal preference.

MILITARY OPERATIONS
Military Operations are rarely troubled by the classical features of Jet Lag, which has been described. Intercontinental air ops are far & few - the most memorable being the bombing of Libya during Op Eldorado, with USAF aircraft flying from England to Libya on a 14 hour round trip! Military ops are likely to face a different kind of Jet Lag, which may be loosely described as "shift operations". Fighter aircraft typically fly sorties lasting up-to 2 hours. Problems relating to long duration sorties are poorly documented in literature. The USAF, US Navy and RAF routinely fly long duration sorties, often with a twin or single aircrew fighter cockpit, e.g. F-15E, F-4G, F-16 and EF-111. Typical sortie duration range from 2.5 h on internal fuel and up-to 8 h with multiple aerial refueling. On Trans-Atlantic flights, the duration may extend to 12 - 17 h.

Such military operations may require to have dedicated set of aircrew - to operate separately for day & night operations. Thus the aircrew starting its duty tour at 1900 h for the next 10 hours may require sleeping in the daytime & therefore, readjust their circadian rhythms. Certain pharmacological measures may be required to ensure reversal of sleep patterns, at least in the initial part of operations. Short acting hypnotics along with melatonin may be required to achieve the operational aim. It may also necessitate changes in operational training & perhaps permit the use of drugs like melatonin with flying duties.

CONCLUSION</