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Q1:
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How does aviation physiology differ from that at sea level & what are its important effects?
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A:
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At 6000 feet, the atmospheric pressure is 609 mm Hg, and at this reduced pressure, gas in body cavities expands as per Boyle’s law. Thus 100 ml of air at sea level occupies about 130 ml at 6000 feet, and problems may arise if it is unable to vent freely. Hence damage, ranging from mild to severe, may occur in various sites of the body secondary to increase in pressure & this is called “Barotrauma”. Fortunately, serious damage is rare; however, even mild cases can be very painful. The commonest site of barotrauma is in the middle ear; the presence of a bad cold prevents pressure equalization & causes severe earache, fullness in the ear, tinnitus, deafness, or even bleeding from the ear due to perforation of the eardrum. Similarly, barotrauma in the paranasal / frontal sinuses can result in headache, pain over the sinuses, or bleeding from the nose. Other symptoms caused by expansion of gases could be abdominal pain, distension, flatulence, severe toothache or lung complications e.g. increase in size of pneumothorax.
The second and much more important & commonly encountered physiological consequence of reduced atmospheric pressure is hypoxia. At sea level the alveolar partial pressure (PAO2) of oxygen is 103 mm of Hg whereas at 6000 feet it is about 75 mm Hg. Though this minimal fall in oxygen saturation is not significant for healthy passengers at rest, passengers suffering from cardiorespiratory problems or severe anemia, may be unable to maintain adequate tissue oxygenation above 6000 ft & their pre-existing condition can be seriously aggravated due to the mild hypoxia. Factors such as smoking & alcohol accentuate the effects of mild hypoxia even in otherwise healthy passengers.
Drying of skin & dehydration may result from low cabin humidities & circadian rhythms are disrupted from rapid crossing of several time zones in long-haul flights. Sleep and appetite are also affected resulting in fatigue.
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Q2:
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How safe is the air you breathe in the cabin of the aircraft?
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The Environmental Control Systems on all Boeing Aircraft are designed to meet / exceed FAA Requirements, & also satisfy all health guidelines set by organizations like OSHA & ACGIH. The cabin ventilation systems provide approximately 50% fresh air & 50% re-circulated air. The re-circulated air passes through High Efficiency Particulate Air (HEPA) Filters to remove bacteria & viral particles, prior to returning to the cabin. These HEPA filters are 99.99% efficient & are similar to those used in hospital operating theatres. There are about 20-30 total air changes / hour for the passenger cabin & 80 changes / hour for the flight deck, this being more effective & superior to air-conditioned offices (12 times / hour) or Operation Theatres (20 times / hour). The ventilation system provides about 10 CFM of fresh air ventilation & 20 CFM total air ventilation / passenger. Levels of bacteria / fungi measured in cabin air are well below the levels accepted as posing health risks, as per US DOT study in 1989 & a recent WHO study found no evidence that air re-circulation facilitated transmission of infectious disease aboard aircraft. The Temperature & relative humidity are maintained at recommended levels.
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Q3:
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What is the definition of an invalid / disabled passenger?
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The term 'Invalid or Disabled Passenger' is used by airlines to denote those passengers who due to sickness or disability may require special assistance or consideration prior to, during, or immediately following an air journey. Invalid passengers may be of 3 types : (a) those who are travelling to obtain treatment for their ailment; (b) those with terminal illness who wish to travel home to die - most airlines will consider such cases sympathetically on humanitarian grounds; (c) those who are travelling for business / pleasure, and whose disability or illness is incidental to their journey. Medical problems are commonly encountered with passengers in the first group, firstly, as they are usually seriously ill and require assistance / medications during the flight, and secondly because the flight environment is 'Hostile' and may significantly affect their condition.
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Q4:
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Are you fit to fly?
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Air travel is generally one of the safest & most convenient methods of travelling. Consequently, an increasing number of passengers with medical problems are opting for this popular mode of transport, without being fully conversant with the potential interaction of their illness with the aircraft environment. Though most of these passengers are able to fly on a commercial aircraft without experiencing much difficulty, special precautions are required to be taken in view of the cabin air being pressurized to maintain an altitude between 5000-8000 ft. Jet Airways requests for medical clearance when fitness to fly is in doubt e.g. following a recent illness, injury, hospitalization, surgery, or a long-standing condition where special facilities (oxygen, special medical equipment, etc) are required. Passengers with heart / lung diseases or breathing difficulties may have an exacerbation of their medical problems due to decreased availability of oxygen in the cabin & are thus requested to get fitness to fly from their treating physicians PRIOR to making a reservation. Passengers with stable, long-standing disabilities e.g. arthritis of the knee, do not require formal clearance & wheelchair assistance can be provided on request. However those who are unable to look after their own needs during the flight e.g. transferring from wheelchair to seat, eating, toiletting, are required to travel with an able-bodied escort.
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Q5:
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How does Jet Airways judge whether you are fit to fly & what special protocols have to be followed in these cases?
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A:
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Due to the large number of invalid passengers travelling by air, Jet Airways in common with other airlines belonging to the International Air Transport Association (IATA), follows laid down common standards of acceptance for such cases and has devised a common medical form and acceptance procedure. All commercial airlines also retain doctors to assist their personnel in making decisions regarding transportation of passengers with noticeable symptoms of sickness / injury. Physicians may contact these doctors by calling or writing to the medical departments of the concerned airlines. On submission of the completed Medical Assistance / Information (MEDA) Form to the airline booking office, the necessary details are transmitted to the airline Medical Department for a decision regarding fitness to fly, and the answer is rapidly transmitted back to the reservations office. Jet Airways’ Doctors are stationed in Mumbai, Delhi, Chennai, Kolkata, Bangalore & Hyderabad.
It is mandatory that ALL invalid / disabled passengers / recently hospitalized passengers get their treating doctors to fill up the MEDA FORM before travelling, so as to avoid last minute refusal / emergency on board. To be of clinical significance, the MEDA Form has to be relatively recent. In addition, all sick passengers / their relatives are required to fill up the INDEMNITY BOND prior to the flight.
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Q6:
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What facilities are available on request for these cases?
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Though airlines do not allow the use of personal oxygen cylinders (as they may not comply with safety regulations), most major airlines will supply extra oxygen cylinders (with fixed flow rates of 2 or 4 L / min) in the aircraft cabin, on (at least 48 hours’) advance written request from the passenger’s physician. Cases requiring oxygen should be accompanied by an escort (preferably medical) who is familiar with the procedure. Arrangement for oxygen during transit will have to be routed through the Airport Authorities of India (AAI). The oxygen cylinders carried on board the aircraft are specially tested & are equipped with special valves to cope with the changing cabin pressure; the oxygen also is of a specific grade. Thus, passengers are not permitted to carry their personal oxygen cylinders in the aircraft. Other facilities such as AMBU LIFT, wheelchairs, special diet, can be arranged for if adequate notice is given.
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Q7:
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How do the space constraints of the aircraft cabin affect invalid passengers?
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The ergonomics of accommodating incapacitated passengers gives rise to most of the problems. There is not a great deal of space for the legs in an economy class seat & thus a passenger with an above-knee leg plaster, an ankylosed knee or hip, or any similar disability, may simply not fit in. Even if he can be accommodated with some effort, it must be remembered that he may have to maintain an uncomfortable position for many hours. Though there is more room in the first class cabin, & certain seats (those in emergency exit rows) have a little more leg room than normal, there are limits on available space & safety regulations prohibit the allocation of seats in emergency exit rows to incapacitated passengers. This is to ensure that emergency exits allow free egress in the event of a rapid evacuation. It is often suggested that a passenger with a plastered leg can be seated so that he can stretch his limb into the aisle of the cabin, but this too conflicts with safety regulations & would certainly inconvenience other passengers & crew. Space is also severely limited in the aircraft’s toilets & passengers with mobility problems may be unable to visit the toilet. This problem can be circumvented by the use of adult diapers / indwelling Foley’s catheter connected to a urinary bag.
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Q8:
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What are the absolute contraindications for air travel?
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Invalid passengers may be refused carriage if there is a possibility that their condition may be (1) Considered a potential hazard to flight safety; (2) Infectious / adversely affect the welfare & comfort of other passengers / crew members; (3) Deteriorate during the flight, with risk of possible diversion / delay of the aircraft or, if it seems likely that death will occur in-flight. This is because the practical & administrative problems associated with an in-flight death may be distressing and inconvenient to all concerned.
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Q9:
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Which conditions are usually considered unacceptable for air travel by commercial airlines & what are the general aviation guidelines?
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1) Patients with acute myocardial infarction are generally not permitted to fly within 6 weeks of the onset of the infarct. Other cardiac conditions where flying is usually not permitted are acute congestive cardiac failure, unstable angina, significant cardiac arrhythmias & severe untreated valvular disease.
2) Patients with incapacitating chronic bronchitis, emphysema, bronchiectasis, or other conditions where respiratory exchange is compromised, may be adversely affected by hypoxia. They are permitted to fly only if arrangements for extra oxygen are made & they are accompanied by a medical escort. Patients with mild, well-controlled asthma can travel without difficulty. However they are requested to carry their own medications on board. Patients with status asthmaticus are not permitted to fly. Patients with active communicable tuberculosis are not permitted to travel by air. The presence of a pneumothorax is a contraindication to air travel (refer to Aviation Physiology).
Exercise tolerance is a good guide to fitness to fly. Breathlessness on walking less than 50 meters on level ground or on rest or the need for supplementary oxygen at sea level suggest that the patient will be severely affected in the aircraft cabin and is unlikely to tolerate the physiological stresses of a long flight.
3) Mentally disturbed passengers may pose problems in two ways – (a) A potentially disturbed psychotic may become a danger to himself & others, especially in the close confines of the aircraft cabin; (b) Psychotics or psycho-neurotics for whom air travel is particularly stressful, may become bewildered, confused or lost during the journey. Psychiatric patients who are well controlled in the sheltered environment of their home or hospital, with regular routines of meals, rest and medication, are ill-equipped to deal with the mental stresses of a long journey, especially by air. Such patients are not permitted to fly unless they are sedated prior to the flight & are accompanied by a trained medical escort.
4) Flying is contraindicated for at least 10 days following abdominal surgery as expansion of gas in the gut will produce abnormal stress on stitches, both in the gut itself and in the abdominal wall. This period may be extended if recovery has been complicated. Similarly, patients are not permitted to fly for at least 3-4 weeks following an acute gastrointestinal hemorrhage. Gas expansion may also lead to hyperactivity of a colostomy or ileostomy and it is advisable for the passenger to carry an adequate supply of bags and dressing in the hand luggage. Patients with gastric feeding tubes may be allowed to fly.
5) Flying is contraindicated for at least 21 days following chest surgery. Again, this period may need to be extended if recovery has been complicated.
6) Patients are not permitted to fly for a period of 7 days after introduction of air into the body cavities (for diagnostic or therapeutic purposes).
7) Flying is contraindicated in the acute phase of cerebral infarction of any etiology (thrombosis, hemorrhage, embolism). A passenger is generally not allowed to fly for at least 3 weeks after suffering from a recent “stroke”. Elderly persons with arteriosclerosis, whose cerebral oxygenation is just maintained at sea level, may become confused after some time at altitude, & this point must be remembered when such a patient is travelling alone on a long journey. Epileptics may be slightly more liable to attacks during an air journey & one must ensure that they have taken their anti-epileptic medications before the flight. Although hypoxia might theoretically lower the threshold to convulsions, this seems less important than the disruption of routine, general stress, excitement & fatigue associated with an air journey. Extra anti-convulsant medications around the time of the journey may be advisable for passengers whose epilepsy is poorly controlled. Patients with closed head injuries and those with cerebral tumours require special nursing care.
8) Patients with fixed wiring of the jaw are not permitted to fly, unless fitted with some quick release mechanism, and accompanied by an escort carrying and trained to use wire cutters in case the patient vomits.
9) Severely anemic patients may not tolerate the slight hypoxia and a hemoglobin level of 7.5g per dl is generally regarded as the lowest acceptable. Much depends, however, on the cause of the anemia, the chronicity of the condition & the length of the flight; many chronically anemic patients (e.g. patients in renal failure) may be permitted to fly with hemoglobin levels as low as 6.5g per dl. Sickle cell hemoglobinopathies may present special problems because of the known predisposition to sickling crisis in hypoxic tissues, and once again supplementary oxygen may alleviate this.
10) Deep Vein Thrombosis (DVT) – This is a serious condition where blood clots form in the deep veins, specially in those of the calf & leg muscles. This problem is not confined to air travel but has been noted in ALL formsof travel as well as NON-TRAVEL situations such as theatre seating. Patients with DVT should not fly, until they are stabilized on anti-coagulant therapy and have no evidence of pulmonary complications. Long-haul flights increase the risk of DVT & may result in embolic disease. Prevention includes wearing of loose-fitting, comfortable clothes, intake of plenty of water or fruit juice, avoidance of smoking or alcohol or coffee, administration of low-dose aspirin (in selected cases), use of appropriate stockings, foot & leg exercises, & walking during the flight. DVT has not been seen in domestic flights as it usually does not occur in short-haul flights of less than 8 hours’ duration. Some people with risk factors (e.g. abnormality of clotting factors, certain types of heart disease, presence of some malignancies, hormonal treatment, including oral contraceptive therapy, recent major surgery [specially abdominal or lower limbs], recent immobilization, pregnancy, obesity, varicose veins) are more prone to develop DVT & should consult their treating doctors before undertaking the flight.
11) Plaster casts need to be slit in case flying is mandated within 48 hours of application.
12) Patients with uncontrolled hypertension or diabetes mellitus are not permitted to fly.
13) Patients with acute sinusitis, acute otitis media, severe catarrhal obstruction of the eustachian tube, immediately after middle ear surgery, are not permitted to fly as this may result in acute barotrauma (refer to Aviation Physiology).
14) Patients with tracheostomy may be permitted to fly, provided they are accompanied by trained medical or paramedical personnel & are carrying a manually operated suction apparatus.
Though these are suggested limiting factors, each individual case is considered on its merits & the final decision whether a passenger is fit or unfit to fly is taken by the 9W Medical Department. This is influenced not only by the nature & severity of the illness, but also on various factors such as the duration of the flight, the availability of supplementary oxygen & other medical supplies, & the presence of an attending physician or trained nursing attendant and other special considerations.
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Q10:
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Are there special guidelines for passengers suffering from diabetes mellitus?
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A:
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On long haul flights, the routine meal and medication schedules can be disrupted. It is advised that these passengers maintain home time throughout the journey and adhere to their regular meal and medication schedules as best as possible. Diabetic meals can be arranged with the airline before departure. Be sure to carry enough quantity of medications to cover the flight duration, in your hand bag. Also note that low blood sugar levels can cause more problems than slightly elevated ones & immediately ask for assistance if you experience symptoms of low blood sugar (feeling faint, sweating, blurring of vision, etc).
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Q11:
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Are there special guidelines for pregnant passengers & neonates?
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A:
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Pregnant passengers near to term are not acceptable because of the risk of their going into labour in-flight, the aircraft cabin being less than ideal as a delivery suite. Airlines vary in their practice, but most would be reluctant to accept a passenger in the last four weeks of her pregnancy. In Jet Airways, expectant mothers are permitted to fly till 36 weeks of pregnancy provided there are no prior complications. After the 28th week of pregnancy, in selected cases, the expectant mother may be required to carry a letter from her treating obstetrician stating that the pregnancy is uncomplicated & that the pax is fit to fly. The letter should also confirm the expected date of delivery. Between the 36th-38th weeks, a pregnant passenger may be permitted to fly provided she has a Fitness to Fly certificate form her treating obstetrician (as above) & is accompanied by a doctor with at least an M.B.B.S degree. Flying is not permitted after 38 weeks.
After a normal delivery, the mother can travel by air as soon as she feels able to make the journey. In Jet Airways, the mother is permitted to fly 48 hours after a normal delivery, provided she has a Fitness to Fly certificate from her treating obstetrician. Air travel may present problems for the baby – in the first 48 hours of life, the neonatal lung may have small areas of atelectasis, leading to ventilation-perfusion inequalities in the lung. As a general rule, it is therefore prudent to wait at least for TWO DAYS & preferably SEVEN before flying, unless the baby has to travel for urgent treatment. If life-saving treatment is mandatory for the infant, the mother may be permitted to fly with the newborn, provided he is certified fit to fly by the concerned pediatrician and is accompanied by a doctor with at least an M.B.B.S degree.
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Q12:
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What are guidelines for carrying life-saving equipment on board?
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1) Personal oxygen cylinders / oxygen concentrators are not permitted to be carried on board due to security reasons.
2) All medical equipment will have to be security checked PRIOR to boarding.
3) Any electronic / battery-operated medical equipment will have to be cleared by engineering to rule out possibility of interference with the avionics.
4) All equipment must be accompanied by a certificate from the treating doctor stating whether it is manual / battery-operated & that the item is a life-saving equipment which the passenger may require during the flight. It should also state that the equipment does not require to be charged during the flight & does not emit electromagnetic radiation which would interfere with the communication / navigation of AC / AC equipment. Manufacturer’s details on equipment should also be submitted.
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Q13:
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Are stretcher cases permitted on board & what are the facilities offered?
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An aircraft stretcher may be the only acceptable method of transporting a seriously ill or severely incapacitated passenger. All stretcher cases must be accompanied by a suitably qualified attendant who can undertake any necessary treatment & nursing care in-flight, as cabin crew are trained only in First Aid, and are not permitted / qualified to carry out nursing duties. This attendant could be a medical / paramedical / non-medical escort, as per the decision of the 9W doctors. Patients with intravenous drips are permitted to fly ONLY as stretcher cases & have to be accompanied by medical / paramedical escort. A stretcher usually occupies 9 seats, thus making such a mode of transport expensive for the passenger. The growth of Air Ambulance Services has largely relieved the pressure on scheduled airlines to carry critically ill passengers or those requiring intensive nursing care in-flight.
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Q14:
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What is the extent of medical assistance that can be rendered by the cabin crew?
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Cabin Crew, though trained in First Aid, are unable to offer nursing services, and are not permitted to give injections or any medications other than those provided in the DGCA approved First Aid Kits on board. They are not permitted to open the Physician's Kit which can be opened ONLY by Registered Medical Practitioners. They are also not expected to give special assistance to a particular passenger to the detriment of service to other passengers, & are not expected to lift passengers or assist them inside the toilet cubicle. If this is required, the passenger will need to be accompanied by a suitably trained medical or paramedical escort. Escorts should ensure that they have all appropriate items or medications for care of their patient & are responsible for attending to all aspects of their bodily needs. Cabin Crew cannot be involved in this as they also handle food.
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