**4.1 Airline Operations:**

Passenger medical emergencies and medical kits

Cabin air quality issues

Passenger comfort (economy class syndrome)

Inflight nutrition and hydration issues (preparation, storage, serving
of meals) including food poisoning

Personal protective equipment and procedures

Disruptive passengers

Crash survival and crash worthiness

Emergency evacuation

Commercial air operations in the United States carry over 700 million
passengers per year and, worldwide, over 1.2 billion. These commercial
operations tie our world together so that, for the first time in human
history, no city is more than twenty-four hours away from any other
city. Carrying passengers safely and efficiently is a complex operation,
requiring close cooperation between the Federal Aviation Administration,
which certifies, regulates, and controls the air transportation system,
and the other components of the aerospace industry: the aircraft
manufacturers, commercial air carriers, and air taxi operators,
airports, reservation-making organizations, and other travel agencies.
The scope of this section will concentrate on the medical aspects of
airline operations.

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Commercial air carriers with twenty or more passengers per aircraft are
governed under Part 121 of the Federal Aviation Regulations and charter
and air taxi operations are governed under Part 135. Certification and
safety standards are identical, although the medical requirements for
the pilot in command of a scheduled airline carrier require that a first
class medical certificate must be held. All other pilots must hold a
second class medical certificate. Any other crew member must be
medically fit to operate their equipment and all safety equipment within
the aircraft. In effect, this means that flight attendants must be
physically capable of seeing, hearing, and performing ably in an
emergency to operate cabin doors, release slides, and other safety
equipment. Flight attendants are not required to hold a medical
certificate and a recent survey indicated that one third of them would
be unfit to hold a third class pilot medical certificate.

The environment of the passenger carrying aircraft is relatively benign.
The cabin altitude is limited to 10,000 feet in pressurized aircraft by
federal regulation, although, in practice, air carriers function with
cabins between 6,000 to 8,000 feet. In most aircraft, the cabin air
pressurization is derived from bleed air taken from the jet engine
compressor. In some aircraft, a small separate compressor engine is
used. In unpressurized aircraft, flight between 10,000 and 12,000 feet
is limited to no more than thirty minutes at a time and oxygen is
required above 12,000 feet. Cabin temperature is generally regulated
through an air conditioning system controlled by the pilots, which
simultaneously regulates air pressure. The relative humidity in
commercial aircraft is low, ranging between 5 and 20%. Acceleration
forces tend to be at a minimum with a standard bank turn of 30° being
the maximum permitted, which imposes the maximum of 1.3 Gz load on the
occupants. Ascents and descents are usually at no greater than 6° nose
up/down pitch angles.

Passenger briefings are required and a flight attendant must be present
if there are forty or more seats and one flight attendant for every
fifty seats in an aircraft. Smoking is prohibited for all scheduled
flights within the United States. Parts 121 and 135 also prohibit
passengers from carrying weapons or interfering with crew members. Any
such actions are subject to detention and potential arrest by Federal
authorities. Disruptive passengers, such as those who threaten others,
become loud and abusive, smoke or disable smoke detectors are also
subject to arrest.

Prior to flight, passenger information briefings must be provided by a
crew member, usually the flight attendant. Passenger information
briefing must include instructions on safety procedures, including the
use of safety belts and emergency oxygen systems, flotation devices, and
emergency exit procedures. This will include the location and the
operation of emergency exits and how to identify emergency exit
lighting. Smoke hoods must be provided for the cabin crew, although they
are not required for passengers.

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Basic Medical Kit

In 1996-97, the FAA conducted a survey of the five largest U.S. air
carriers and reviewed 1132 in-flight medical emergencies. The use of
bronchodialator inhalers, antihistamines and non-narcotic analgesics led
to the recommendation of their inclusion in a larger and more robust
emergency medical kit. Upgraded Emergency medical equipment is required
on commercial airliners with twenty seats or more, as of 2004. This
includes an automatic external defibrillator (AED), a primary medical
kit, and an advanced medical kit. Cabin crew must be certified in
cardiopulmonary resuscitation, use of the AED, and contents of the
primary medical kit. The primary medical kit will consist of minor
medical items, such as a stethoscope, blood pressure cuff, Band-Aids,
bandages, and analgesics such as aspirin or acetaminophen.

The advanced medical kid is a "crash kit", such as the Banyan 600 or
equivalent, containing advanced cardiac life support medications,
airways, laryngoscope, and such drugs as the airline elects to utilize.
The carriers are not required to provide any specific pharmacy items and
may elect to exclude controlled drugs. The medical kits and AED are
typically kept in a locked overhead compartment, which is accessible by
a key held by all of the flight crew members. The advanced medical kit
is accessible only by a licensed medical provider, that is, M.D., D.O.,
D.D.S. or a nurse practitioner. The pilot in command may elect to permit
other knowledgeable medical persons to open and use the advanced medical
kit at their discretion.

Many commercial airlines utilize an air to ground communication system
that connects the aircraft to an emergency medical consultant on the
ground, using commercial contractors like Med-Air or MedSTAT. These
services provide telecommunication with a medical consultant on a real
time basis. In the event of an in-flight medical emergency, however, the
pilot in command of the aircraft bears the ultimate responsibility for
any decisions, regardless of medical advice provided from an onboard
physician or consultant on the ground.

Cabin air quality and comfort issues remain a subjective condition.
Comfort may mean different things to different people. One individual
may like a warm humid environment, while another prefers it cooler. The
aviation industry is faced with a dilemma: when the temperature of an
aircraft cabin is set at a level to make a sitting and inactive
passenger comfortable, it may be too warm for the physically active
flight attendants. Cabin pressurization is typically set between 6,000
and 8,000 feet or 565 mm/hg. The oxygen percentage remains 21% and, in
the normal person, oxygen saturation will remain at or above 90%.
However, there is a subset of the population that will desaturate at
between 5,000 and 8,000 feet and demonstrate hypoxic symptoms. This has
not been demonstrated to be a health hazard nor has repeated exposure to
lower cabin pressures on an occupational basis been demonstrated to be a
hazard to the flight crew.

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Aircraft Environmental Control Systems

The cabin is ventilated and fresh air continually plumbed into the
cabin. Some of the air is recirculated in modern aircraft, as it is in
most modern buildings. The purpose of this circulating air conserves
energy in the form of heat, as well as less air "robbed" from the
compressor section of the jet engine. The fuel savings can be very
significant, up to near 40% in modern aircraft such as the Boeing 777
and the Airbus 320. A typical ratio of fresh air to recirculated air can
be up to 50/50. Compare this to a typical modern commercial building
where there is 20% fresh air and 80% recirculated air. Recirculated air
is air that was removed from the aircraft cabin. Some is dumped
overboard while the remainder is pumped through high efficiency
particulate air filters (HEPA), which remove over 99% of all
contaminants, including bacteriologic agents. The oxygen percentage in a
50/50 cabin of a modern commercial airliner that is at maximum load
capacity will not drop below 20.5%.

There are potential contaminants in the aircraft cabin. These include
carbon monoxide. However, typical carbon monoxide levels in jet aircraft
are extremely low and typically under ten parts/million. The major
source of carbon monoxide is cigarette smoke and with a total ban on
smoking in American aircraft and recommended worldwide by the
International Civil Aviation Organization, carbon monoxide contamination
should be a problem of the past. Carbon dioxide also exists in the
aircraft cabin. There are two primary sources for carbon dioxide. The
major source is human respiration. The second source is carbonated
beverages and dry ice. The maximum allowed concentration of carbon
dioxide is 1,500 parts/million, although this does not actually
represent a health hazard. Carbon dioxide is also used as a surrogate
marker for body odors, which cannot be easily measured. Measuring carbon
dioxide is difficult and care must be taken not to place the sensors too
close to the occupants, as exhaled human breath is typically 2% (20,000
parts/million) carbon dioxide. Ozone, a substance found at high
altitude, may be pumped into the aircraft ventilation system. This can
be easily removed by placing a catalytic converter in the line.

Other chemicals, such as volatile organic compounds and multiple sources
from food, lubricants, off gassing of clothing have been observed. In
aircraft where smoking is permitted, cigarette fumes are the primary
source of volatile organic compounds. Insecticides are used in some
aircraft for disinsection when the cabins are sprayed on arrival at an
international port of entry. The primary chemical used is a synthetic
pyrethrin. The World Health Organization continues to support the use of
disinsection to prevent importation of disease vectors.

The aircraft cabin has also been reviewed as a potential source of
disease spread. Biological contaminants do circulate within the aircraft
cabin. It is clear that the low humidity in an aircraft cabin reduces
the transmission ability of many biologic agents. The major concern has
been tuberculosis and between 1992 and 1994, Centers for Disease Control
and Prevention conducted seven investigations, reviewing potential
spread of tuberculosis in aircraft. There were 2,600 potentially exposed
passengers and crew on a total of 191 flights, with nine different
aircraft. A total of one flight attendant and six passengers converted
skin tests on two of these flights. There were no active cases of
tuberculosis. An additional investigation of a pilot with active
tuberculosis was reviewed by a corporate medical director as the flight
deck air supply was separate and the aircraft in question, a DC-9 had
non-recirculating air. The pilot in question, over a six month period
before he was identified, had flown with forty-four other pilots. Of the
forty-four, thirty-five did not have previously positive tuberculin skin
tests and none of them converted. Of the nine with preexisting positive
skin tests, all had unchanged chest x-rays. Clearly, the
transmissibility of tuberculosis in the aircraft cabin is a possibility,
but an event on a low order. Active cases of tuberculosis should be
treated for a minimum of three weeks with multi-drug therapy and have
non-viable organisms in their sputum before being permitted to travel or
be about in public areas.

Another disease was influenza. In a 1977 case, 72% of an aircraft
passenger cabin became ill after an index case boarded the aircraft.
This was an unusual event, as the aircraft was delayed on the ground for
three hours with a non-functioning ventilation system, allowing an
unusual pattern of spread that would not normally be seen.

Food and beverages are supplied to passengers and crew in flight. Food
preparation is important here as in any public restaurant. In a unique
event, in 1992 a plane departed South America bound for the United
States had been supplied with seafood contaminated with cholera
bacteria. The resulting outbreak was the largest in America in the
20^th^ century with 75 cases and one death.

Food service affects the aircraft operation. The aircraft may not be
moved on the ground, takeoff or landing when any food or beverage is
located in a passenger seat and passenger food trays must be stowed with
an aircraft moving on the ground or in the approach or landing portion
of the flight. Alcoholic beverages may be served, but the certificate
holder is the only permitted source of alcohol. Passengers may not bring
their own alcoholic beverage onboard nor is an intoxicated passenger
permitted to board an aircraft. Food must conform to basic sanitation
and food handling rules. Specific equipment for food and beverages is
required. For example, a coffee maker on a commercial aircraft may cost
thousands of dollars, as it must have a latch to secure the coffee
container, which itself must be unbreakable and unpressurized. Many a
general aviation pilot has taken a thermos of coffee along on a flight,
only to open it and have the now pressurized hot coffee spray all over
the cockpit.

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In flight passenger medical emergencies are rare, but do occur. A
1999-2000 survey by the Air Transport Association estimated that one
passenger in every 300,000 experienced a significant medical problem in
flight and that one in every 3.5 million would have a life-threatening
emergency. This compares to approximately 1 in 150,000 in the United
States general population on a daily basis. The difference primarily
speaks to the nature of the population flying as passengers. Terminally
ill and extremely debilitated persons are more likely to be found in
hospitals than on board aircraft. The American with Disabilities Act and
the Air Carrier Access Act have increased greatly the number of disabled
and debilitated individuals who fly. In flight medical events are most
commonly cardiovascular, neurologic and pulmonary in nature. Most
pulmonary conditions are asthma or chronic obstructive pulmonary
disease. Many of these are attributable to non-compliance with
prescribed medications. Passengers may request supplemental oxygen in
flight. However, the oxygen must be prescribed by a licensed physician
and must be provided by the air carrier. Passengers may not bring their
own oxygen system on board the aircraft. Air carriers are not obliged to
provide oxygen in flight and those that do will limit the maximum flow
rate typically to eight liters/minute. Additional costs are assessed to
the traveler requesting oxygen.

A simple measure of whether an individual can fly with supplemental
oxygen is to have the passenger walk one hundred yards at a normal pace
or climb one flight of stairs. If they do not become short of breath,
they have adequate pulmonary reserves. Travelers should be reminded to
maintain hydration, drinking constantly throughout the flight. Cardiac
disease is the second most common cause of in-flight medical conditions.
Travelers should carry their medications with them and consult with
their physician prior to traveling. New York Heart Association class 3
and 4 should strongly consider the necessity of traveling with a medical
attendant or utilizing an air ambulance. If a pacemaker is installed,
the airline should be notified in advance.

Neurologic conditions include seizure disorder. Most seizures in flight
are due to patient noncompliance and due to difficulties with controlled
substances. Anti-seizure medications are not necessarily carried, even
in the advanced medical kits. Psychiatric disorders are generally safe
to fly. However, individuals who are unstable and constitute a threat to
themselves or others should not fly. Individuals with ear, nose or
throat conditions or recent surgery may be subject to problems with
cabin pressure changes and, again, advised to consult their physician
prior to flying.

Pregnant travelers should consult with their physician. Turbulence in
flight is not uncommon. In addition, it is inadvisable to travel by air
after the thirty-sixth week of pregnancy. An airplane is not a delivery
suite. Those women with a history of complications or premature delivery
should not fly at all. Pregnant patients are at significantly increased
risk for deep venous thrombosis, regardless of whether traveling by air
or not.

Deep venous thrombosis is an intrinsic risk for many individuals. Those
with abnormal clotting factors, pregnancy, smoking, obesity, hormone
replacement, and recent lower leg trauma or surgery, as well as those
with cancer and coronary artery disease, are at significantly increased
risk. Prolonged immobilization can promote the formation of deep venous
thrombosis, not only in an airplane, but in any other similar situation.
While some researchers have implied that high altitude and low humidity
of an aircraft cabin promote the formation of deep venous thrombosis,
this has not been verified scientifically or epidemiologically. Deep
venous thrombosis and pulmonary embolism have been demonstrated to occur
in the general population and account for 6 to 14% of all deaths,
depending on autopsy series. In order to minimize the risk of deep
venous thrombosis, the Aerospace Medical Association recommends
exercising the legs by flexing and extending the ankles at regular
intervals, getting up and walking about the cabin periodically on longer
flights, avoiding sleeping in a cramped position or the use of sleeping
aids, and maintaining adequate amounts of hydration with water and fruit
juices. They recommend avoiding dehydrating drinks such as alcohol or
caffeinated beverages. Other devices, such as compression stockings and
anti-coagulant medication have been recommended, but have not been
demonstrated scientifically to be effective. While deep venous
thrombosis has been termed "economy class syndrome", the rate of DVT
among all travelers is the same, regardless of first class, economy
class or crew and the intrinsic risk factors of the individual passenger
are the best predictor of risk. Accordingly, this has been termed
"traveler's thrombosis."

Decompression sickness or the bends is a great risk for individuals who
have been scuba diving. Divers who have been on a single dive of less
than thirty-three feet sea water and not requiring a decompression stop
should wait a minimum of twelve hours prior to flying. All other divers
should wait at least 24 hours prior to flying.

Absolute contraindications to flight by passenger for medical reasons
include active communicable disease; recent surgery, with retained gas
within the brain or eye or surgery without being cleared by the treating
surgeon; recent heart attack, and any other unstable medical or
psychiatric condition.

Passengers should carry their medication with them in its original
container, with a prescription label. If they have a significant medical
problem, an abbreviated copy of the medical records should be carried on
their person. Airlines should be alerted 48 hours in advance of any
special requirements, with provisions for extra time if pre-boarding is
requested. Special seating arrangements may be requested for passengers
with mobility problems. For example, passengers who require a wheelchair
may be boarded first and will be transferred to the aisle chair, a
special narrow wheelchair designed to be moved down an aircraft aisle.
The armrest on aisle seats can be lifted, allowing a mobility impaired
passenger to be transferred from an aisle chair into a regular passenger
seat. Typically, mobility impaired passengers are seated in the front of
bulkhead row to provide more room for attendants to assist the passenger
in transfer. Paraplegic passengers will typically prefer the aisle row
seat, as it is easiest for them to affect their own transfer.
Quadriplegic patients and passengers will prefer the window seat, as the
cabin wall provides more support for them in flight.

Commercial airlines are required to accommodate all disabled passengers,
but a disability in and of itself does not give a passenger more rights
than any other. For example, passengers who are severely obese may be
directed to buy a second seat if their physical presence actually
occupies two seats. A passenger requiring oxygen may be denied travel on
an airline that does not provide oxygen. Stretcher patients currently
may only travel on one United States carrier (Northwest), as no other
commercial carriers currently permit this service.

A passenger who experiences an in-flight medical problem may cause the
aircraft to declare an emergency. The pilot in command will declare an
emergency and air traffic control will provide them priority routing for
immediate landing at the nearest suitable facility. Medical resources at
the airport will be alerted. All controlled airports in the United
States are required to have a fire/rescue capability of responding to
any point on the airport rounds within three minutes. Additional
in-flight resources can consist of the pilot descending the aircraft
physically, as well as lowering the cabin altitude as quickly as
possible. Flight attendants can provide Cardiopulmonary resuscitation
(CPR) and first aid. Medical personnel on board the aircraft (there is a
statistical 78% chance that a physician will be onboard a flight and a
98% chance that some other medically qualified person will be on board
the flight) can provide in-flight medical attention and ground-based
emergency resources can be consulted. Oxygen can be provided by
emergency oxygen tanks on board the aircraft. The drop down masks used
for cabin depressurization incidents may not be used for an emergency
medical condition. In any event, they contain between 8 and 15 minutes
of low pressure oxygen supply.

Airlines take reasonable precautions to avoid in-flight medical
emergencies. The majority of such emergencies are unforeseeable or the
potential was known only to the passenger prior to embarkation. Because
of the potential of emergency evacuation of an aircraft, disabled
passengers are not permitted to be seated in the emergency evacuation
rows and there are no primary provisions for evacuating those who are
movement disabled. This is a risk that these individuals must accept in
order to fly.

References

Aerospace Medical Association, "Medical Guidelines for Airline
Passengers", Alexandria, VA 2002.

Bagshaw, M., Travelers Thrombosis, A Review of Deep Vein Thrombosis
Associated with Travel, Air Transport Medicine Committee, Aerospace
Medical Association, Alexandria, VA 2002.

Bendz, B., Rostrup, M. et al., Association Between Acute Hyperbaric
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DeJohn, C.A., Véronneau, S.J.H., Wolbrink, A.M., and Larcher, J.G.
DOT/FAA/AM-00/13: The evaluation of in-flight medical care aboard
selected U.S. air carriers: 1996 to 1997. Civil Aeromedical Institute,
Federal Aviation Administration, Oklahoma City, OK. April 2000.

House of Lords: Science and Technology -- Fifth Report on Air Travel and
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Kenyon, T.A., Valway, S.E., Ihnle, W.W. Transmission of Multi
Drug-Resistant Micobacterium Tuberculosis During a Long Airplane Flight.
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Kraaijenhagen, R.A., Haberkamp, D. et al., Travel and Risk of Venous
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Mohler, S.R. Chapter 24 [Civil Aviation Medicine in Fundamentals of
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Pheby, D.F.H., Cobling, B.W., Pulmonary Embolism at Autopsy in the
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Scurr, J.H., Machin, S.J. et al. Frequency and Prevention of Symptomless
Deep Vein Thrombosis and Long Haul Flights: A Randomized Trial. [The
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Thibeault, C. Airline Cabin Air Quality. Occupational Medicine State of
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Wicks, R.L., Irvine, L.A. Microbiological Composition in Airline or
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