that he occasionally became weak and tremulcus, ard that, at work while
seated at a desk, he had been noted to be pale and tremulous and to

have said something about tachycardia (fast heart rate). Medical

information on this pilot in the Certification Branch of the FAA Civil
Aeromedical Institute showed that he did not reveal, nor did his examining
physician find, any condition that disqualified him from flying. However,
records in one hospital showed that he had indicated he had “always“ had
heart trouble, and records in another hospital revealed an electrocardiogram
that showed a condition of atrial fibrillation (the basic cause of the fast
heart rate) and treatment that converted his heart back to a normal rate. In
a physician's office was a printed record indicating that the pilot's
condition of tachycardia occurred as often as several times a week and that
he occasionally passed out with it. It was then obvious that this acrebatic
pilot had a heart condition that on occasion led to loss of ccnsciousness.
Such a condition could not be discerned by autopsy examination but was only
revealed by the medical history. The most probable cause of the accident

was that the pilot in doing his maneuvers set off the condition of atrial
fibrillation in his heart. The heart then became an inefficient pump unable
to supply enough blood and thus oxygen to the brain to maintain consciousness,
the pilot passed out, and the plane flew itself into the ground. Of course,
a major reason for the medical certification of pilots is to eliminate from
flying those with a medical condition that will significantly reduce the
safety of flight. Accident investigators should always try to rule out such
conditions by obtaining autopsies. But investigators should be cognizant

of the shortcomings of autopsy procedures and aware that even in the most
common form of incapacitation--sudden heart attack, collapse, and death--a
pathologist most often cannot say unequivocally that death was due to the
heart attack. Ancillary medical information such as the findings of medications
and medical history may be of paramount importance in discerning what may have
happened to the pilot.

A second broad area of incapacitation is what I term physiological
incapacitation. Spatial disorientation (or "pilot vertigo") is probably the
most common manifestation in this category and is a “cause" in 16 percent of
fatal accidents coded by the NTSB. Spatial disorientation is a failure of
the pilot to perceive his/her attitude, motion, and speed in relation to the
earth; it most frequently occurs when visibility of orientating references
outside the aircraft, such.as the horizon or ground, is impaired by ciouds,
fog, snow, rain, etc., or by darkness. All persons, under laboratory conditions
with vision obscured and subjected to linear and/or angular acceleration, can
be made to experience bothersome disorientation as a function of the semi-
circular canals and associated vestibular sensory apparatus in the inner ear.
The same type of disorientation occurs in flight and may markedly impair the
pilot's ability to maintain the aircraft at a safe operating attitude and
speed. Indeed, spatial disorientation is coded by the NTSB as the third most
common “cause" of fatal aircraft accidents. I like to think of spatial
disorientation as part of a triad, using NTSB terms: “initiated flight into
adverse weather"; “continued VFR flight into adverse weather"; and “spatial

2



Cocaine, heroin, barbiturates, and other habituating drugs are
routinely screened for in accident victims, but positive results are
unusual. Marihuana is a drug of more widespread use, but it has been
difficult for toxicologists to verify intake by identifying the active
ingredient tetrahydrocannabinol or a metabolite in postmortem specimens.

If a victim is suspected of having smoked warihuana, alcohol swabs may be
made of the fingers, lips, and mucous membranes of the mouth. A relatively
simple chemical reaction can detect marihuana ingredients extracted into

the alcohol, but this test is qualitative and only heightens one’s suspicion
that the pilot may have been influenced by marihuana. Other evidence in the
form of pipes, papers, and marihuana leaf residues may be corroborative. In
the exceptional case, specimens from accident victims can be sent to
laboratories conducting research on marihuana. Such laboratories in the
Past have been able to confirm the presence or absence of the active
ingredient in the blood of pilots and vehicle operators.

Of interest to the FAA, which is responsible for the conduct of a
program to medically examine and certify pilots, are means of monitoring
standards of certification. To this end we maintain a keen interest in autopsy
and toxicologic findings in fatal pilot accident victims. For example, in the
last year three captains of air carrier aircraft died cardiac deaths while
their aircraft were in flight. Each of these pilots, as with all air transport
Pilots, had undergone a certifying medical examination within 6 months before
his death.

One means of monitoring for medical conditions is to examine specimens
from fatal pilot accident victims for the presence of drugs. The finding of
quinidine in the blood of a pilot probably indicates he or she was being treated
for a cardiac arrhythmia. Mood-elevating drugs may reflect some psychiatric
problem. Thus, the finding of a drug in an accident may suggest a medical
condition that may have disqualified the pilot from medical certification--a
condition that may not have been revealed by the pilot undergoing certifica-
tion examination. Indeed, the withholding of information from the aviation
medical examiner could influence the settlement of injury claims and alter
the liability of a pilot involved in an accident.

Because therapeutic drugs are used at fairly low doses it is frequently
difficult to detect the drug in the specimens submitted for toxicological
examination. The thorough accident investigator will look among the pilot's
personal possessions for pills, tablets, liquids, ointments, etc., which may
suggest the type of drug the laboratory should concentrate on in attempting
to identify materials in the postmortem specimens. Not infrequently the drugs
found will suggest some condition that can lead to unfolding of a significant
medical history. Drugs and disclosure of a medical history could add
significance to the autopsy findings. For example, a commercial pilot was
flying a large aircraft with passengers aboard. At a critical point in the
flight, control was lost, the plane crashed, and everyone aboard was killed.
The autopsy revealed markedly diseased coronary arteries, but this finding

7



serve accident investigation can be used and where personnel are alert to
the significance of findings to the accident and thus avoid the difficulties
encountered when laboratories not versed in forensic procedures attempt to
evaluate an occasional specimen. Reports of toxicological analyses are
part of all accident records and are available to all persons who seek to
review such records.

Rarely a pilot may encounter something in the environment that may impair
his or her ability to function. For exemple, in flight, a physician pilot
was partially incapacitated by the fumes when the cork in a can of previously
opened ether dislodged in his medical bag at altitude. He safely landed his
aircraft. A large cargo aircraft was lost and its crew of three were killed
when a bottle of nitric acid leaked onto packing materials giving rise to
heat, smoldering fire, and fumes which impaired respiration and vision of the
crew. A small jet cargo pilot taxiing toward the runway for takeoff became
extremely short of breath and returned to the ramp. His cargo consisted of
meat maintained in a frozen state by dry ice: solid carbon dioxide. In the
enclosure of the aircraft cabin the carbon dioxide was mounting in concentration
and could heve asphyxiated the pilot had he not aborted his flight.
Lithium-sulfur dioxide batteries have been removed from aircraft as a source
of power for emergency locator transmitters because of a tendency to explode
or leak sulfur dioxide into the cabin. Sulfur dioxide potentially could
incapacitate occupants. Careful investigation of all factors associated with
an accident shoald give clues that would lead to suspicion of a rare event as
illustrated by these cases.

Five to seven percent of the exhaust gases of an internal combustion
engine is carbon monexide, and, when the engine exhaust is used as a source
of cabin heat, a cracked heat exchanger can introduce this toxic gas into
the cabin where it is breathed by the aircraft occupants. Carbon monoxide
combines with the hemoglobin of blood to form carboxyhemoglobin, reducing
the blood's ability to carry oxygen. A heavy smoker possibly may have. up to
10 percent carboxyhemoglobin. At 20 percent carboxyhemoglcbin, a person may
experience tightness around the head, and headache. At 30 to 35 percent he/she
may experience nausea and vomiting and shortness of breath. At about 45
percent he/she will become unconscious, and at 65 to 70 percent: death will occur.
The value of a routine determination of carbon monoxide on all aircraft
accident victims can be illustrated by an accident in which three occupants
were flying at night and, under frequent guidance from air traffic control,
were avoiding some rain clouds. Communication with air traffic control ceased
and within 2 minutes the aircraft disappeared from the radarscope and crashed.
Investigators sent routine blood samples from two occupants to the laboratory
and noted that there had been fire at the crash site. The laboratory found
40 to 45 percent carboxyhemoglobin in these victims. Without so stating in
the report, the laboratory surmised the victims were trapped in the aircraft
in a postcrash fire (the most common cause of elevated carboxyhemoglobin .
levels in accident victims). Later, autopsy information available to the
laboratory revealed that all. occupants of the aircraft were partially

4



disorientation." Spatial disorientation appears to be a factor in at
least 35 percent of fatal weather-related aircraft accidents (1) and is
frequently associated with in-flight breakup in the absence of thunderstorms
and turbulence. Accident investigators and those reviewing accident data
should be acquainted with this condicion which takes so many lives in
general aviation.

Hypoxia, that is, lack of sufficient oxygen, is undoubtedly the most
serious physiological threat to flight safety in aircraft operating above
15,000 feet but is of considerably less significance in most civil general
aviation accidents. However, there have been well-publicized cases of
aircraft flying at high altitudes for a considerable time before they crashed.
In such an event the first suspicion is that there is a failure of the cabin
pressurization system or oxygen supply resulting in in-flight unconsciousness
and possibly death in the pilot (and passengers). For the most part there is
no way of determining by autopsy whether an accident victim suffered hypoxia.
Military accident investigators usually try to obtain and analyze brain
tissue for lactic acid which, if elevated, may indicate metabolic changes
reflecting the hypoxic condition. Similar toxicologic determinations are not
made on the victims of civii aircraft accidents, and, for most civil aviation
accidents, if the investigator is to invoke hypoxia as a cause of the accident,
he/she must base this on the operating altitude of the aircraft and findings in
pressurization or oxygen equipment. A point to consider, however, is that an
older pilot or one with constricted coronary or cerebral arteries may be more
susceptible to the effects of hypoxia, because of reduced blood flow through
the heart or brain, than a person who does not have these changes, so that
autopsy findings may be consistent or supportive as part of other findings in
the accident-causing milieu.

Toxic factors represent a third broad category of causes of pilot
incapacitation, and they are frequently involved as a cause or factor in
civil aircraft accidents. Such toxic factors can come from cargo carried in
the aircraft, toxic gases resulting frem fire or defective equipment, alcohol
or drugs consumed by the pilot, legitimate medications taken by the pilot,
etc. To monitor such factors in civil aviation a forensic toxicology unit
was established some 13 years ago in the Aviation Toxicology Laboratory of
the FAA Civil Aeromedical Institute in Oklahoma City. This unit prepares and
maintains a supply of toxicology kits in all FAA and NTSB offices where
aircraft accident investigators are based. Everything a physician or
pathologist needs in order to collect and return blood, urine, gastric con-
tents, tissues, and other biologic samples to the laboratory is contained in
one of these “tox boxes." A small amount of ice in this styrofoam-lined
container will preserve specimens in a satisfactory condition (for analysis)
for 3 days even in hot weather. Currently, specimens for toxicological
analyses are received from about 65 percent of pilots killed in aircraft
accidents. Accident investigators should make a conscientious effort to
see that specimens are collected from accident victims and that specimens are
sent to the FAA laboratory, where analytical procedures designed primarily to

3



ee ee eee eS ee

Or poisoning may be gradual as in a pilot who is exposed to small amounts
over a period of time. In the latter instance the effects are cumulative.
This can be documented by having the laboratory make blood cholinesterase
determinations before and several times during the working season. Ina
somewhat careless pilot the cholinesterase level may fail to half its
preseason value. Some pilots who experience headache, blurring vision, and
chest tightness, the early symptoms of insecticide poisoning, may take
atropine orally to alleviate these symptoms. Although this treatment may
relieve the symptoms, it is dangerous in that the pilot's reserve of
cholinesterase remains low and he/she may thereafter be completely incapacitat -d
by additional exposure to insecticide which otherwise would not cause such
complete incapacitation.

In all aerial application accident victims, blood should be collected
for cholinesterase determinations. Most accident investigators realize
this, and it becomes fairly routine that such determinations are made.
However, interpretation of the significance of the laboratory determinations
is questionable without a preseason value with which to compare. Many operators
encourage pilots to obtain preseason and periodic determinations during the
course of their work activities.

Pilots may elect to take into their systems chemicals that may alter
their mood and impair their performance in flying an airplane. In this respect
alcohol is the drug of greatest abuse. Statistical treatment of alcohol values
in pilots killed in civil aviation accidents indicates that about 9 percent
of the pilots have blood alcohol levels about 0.05 percent, a level that has
been determined to affect the ability of a pilot to fly an aircraft. About
20 percent of pilots killed in aircraft accidents have some alcohol in their
systems (3).

When iow levels of alcohol are obtained certain questions are cogent.
Does this level reflect what was truly in the pilot's blood and system, or
does the level signify some degree of laboratory error, or was the alcohol
perhaps the result of bacterial fermentation that occurred between the time
the pilot was killed and the time the blood was analyzed in the laboratory?
These are legitimate questions, and those investigating aircraft accidents
shovld be prepared to make some statement as to the significance of such
findings. The findings can possibly be corroborated by investigation of the
background of the pilot and particularly by defining any drinking history
in the 24 hours before the accident. In the laboratory we attempt to add to
the validity of the determination by culturing the microorganisms out in any
blood sample that has a significant level of alcohol. Once bacteria are
obtained they are put into a broth containing sugar and the alcohol obtained
is analyzed. If the bacteria are capable of producing alcohol, it is
considered that low levels of blood alcohol may not reflect a precrash blood
alcohol level, but instead a postmortem artifact of bacterial contamination.
Bacteria seldom produce high levels of alcohol so that high postmortem levels
of blood alcohol most often reflect high levels of alcohol in the antemortem
blood.



FAA-AM-80-6

MEDICAL A ) TOXICOLOGICAL FACTORS IN AIRCRAFT ACCIDENTS

William R. Kirkham
Civil Aeromedical Institute
Federal Aviation Administration
Oklahoma City, Oklahoma

AAN8 7696

APRIL 1980

Document is available to the public through the
National Technical Information Service,
Springfield, Virginia 22161

Prepared for 3
U.S. DEPARTMENT OF TRANSPORTATION 5
Federal Aviation Administration
Office of Aviation Medicine
Washington, D.C. 20591

Doe rue cord

“ect Le cpwernas senuisintbctes ratio

308 8 O1G


REFERENCES,

1. Kirkham, W. R., W. E. Collins, P. M. Grape, J. M. Simpson,
and fT. F. Wallace. 1978. Spatial disorientation in general
aviation accidents. Aviation, Space, and Environmental
Medicine, 49(9):1080-1086.

2. Kirkham, W. R., D. J. Lacefield, and C. R. Crane. 1979.
Toxicological and pathological findings in aircraft accident
victims that indicate incapacitation from burning interior
materials. Paper presented at the 50th Annual Scientific
Meeting of the Aerospace Medical Association, Washington,
D.C., May 14-19.

3. Lacefield, D. J., P. A. Roberts, and C. W. Blossom. 1975.
Toxicological findings in fatal civil aviation accidents,
Fiscal Years 1968-1974. Aviation, Space, and Environmental
Medicine, 46(8) :1030-1032.

a sb

itd

U.S, GOVERNMENT PRINTING OFFICE :1980- 322~441/6312 9



in itself could not be interpreted as indicating cardiac incapacitation

in the pilot. In the pilot's possessions the investigators found a bottie
of peritrate, a drug commonly used by persons experiencing recurrent heart
pains, and some chemically impregnated paper used for testing the urine

for sugar. This latter is suggestive of the pilot's having diabetes mellitus,
a condition that accelerates coronary artery disease. Comparison of fracture
patterns in the pilot and copilot revealed minor fractures in the pilot's
hands, whereas the copilot had large fractures of the arms and both thumbs
were fractured, the latter suggesting he had his hands on the controls as the
aircraft crashed. The most probable cause ef the accident was sudden cardiac
incapacitation in the pilot. Of course no one item of evidence was adequate
to establish this--it took a combination of autopsy findings and information
gathered at the accident scene.

From the foregoing discussion it should be clear that when there is a
failure in the man-machine combination that leads to an accident, it is
most often the man that fails to perform adequately. Such failures may
reflect a physiological, medical, or toxicological incapacitation. In fatal
accidents, investigators should insure that the man--the pilot and other
occupants--is adequately examined. Such examinations should entail autopsy
and toxicological examination of the victims. However, neither of these
procedures in itself is adequate. fhe investigator must combine information
gathered from these procedures with other information such as flight
characteristics, impact dynamics, fire, weather, medical history, and other
ancillary findings at the scene to give each portion of data its most
meaningful role in establishing the causes and factors operating to bring
about the accident.



decapitated by the impact. Realizing that such injuries would have caused
instantaneous death (and thus cessation of respiration) and that the
carbon monoxide accumulation must have occurred in flight, the laboratory
so informed the investigators, who went back to the wreckage and found and
verified a defective heat exchanger.

Of course carbon monoxide is frequently found in aircraft accident
victims who are alive and breathing in an environment where there is fire
and smoke; that is, they survive the impact but die in the postcrash fire.
This happens in both large air carrier aircraft and small aircraft.
Toxicological examination of specimens, combined with autopsy information to
elucidate the extent of trauma, is needed to assess the relative importance
of the trauma and the toxicants in the demise of the occupants. Human
factors investigators in large passenger aircraft attempt to gather such
information in reconstructing the large-aircraft postcrash survival scenario.
Whenever the carboxyhemoglobin (indicating a significant level of carbon
monoxide) is above 10 percent in any aircraft accident victim, a determination
is made of the hydrogen cyanide in the specimen. It is well accepted that in
fire environments there are gases other than carbon monoxide and, depending
on the materials burning, there may be hydrogen cyanide, hydrogen sulfide,
hydrogen bromide, hydrogen chloride, hydrogen fluoride, acrolein, formaldehyde,
sulfur dioxide, and other toxic and irritating gases. In a number of
large-aircraft accidents where lives were lest, significant levels of hydrogen
cyanide have been found in the blood of victims (2). What an accident
investigator should remember is that, although an aircraft occupant's body
may be charred, an autopsy should be done. The victim could have died of
natural or unnatural causes before the crash; the victim could have died of
impact injuries and thus have been a passive figure in the fire; the victim
could have received considerable injury in the impact and died of inhaling
smoke; or the victim could have escaped injury by the impact but died as a
result of exposure to the smoke and fire. The autopsy to determine the extent
of impact injury, and examination of respiratory passages which are frequently
blackened by soot deposits on their surfaces, combined with the laboratory
determinations of carbon monoxide and hydrogen cyanide, can aid the investiga-
tors in reconstructing the time and dynamics of the deaths.

Aerial application pilots are a special case in:terms of incapacitating
factors in. the environment. Many of the materials they apply to crops from
their aircraft are designed to kill insects or have a harmful effect on
certain types of growing plants. Pilots and other aerial application workers
may be poisoned by the very substances they are applying. Such poisoning may
occur at any of a number of stages of their activities.

The most dangerous of the materials they apply are the cholinesterase-
inhibiting insecticides. Both the carbamate and the organophosphate
insecticides inhibit cholinesterase, an enzyme essential for nerve impulse
transmission and body activities. Poisoning of workers.may be overwhelming,
as in a young flagman who spilled some organophosphate insecticide on. his
arm, absorbed the material through his skin, and almost died 24 hours later.

5



MEDICAL AND TOXICOLOGICAL FACTORS IN AIRCRAFT ACCIDENTS*

The National Transportation Safety Board (NTSB) has determined that
the pilot is a “cause" of accidents in about 83 percent of nonfatal
accidents and 87 percent of fatal accidents.** Because of this, aircraft
accident investigators and those reviewing the findings in aircraft
accidents should pay particular attention to information that indi-
cates the competency of pilot performance. A number of factors within
the pilot may impair his or her ability to operate the aircraft in a safe
manner. The pilot may suffer varying degrees of partial incapacitation
up to total incapacitation at which point he/she loses all ability to
effect control of the aircraft. When complete incapacitation occurs
in the single-member-crew situation, the condition most likely results
in a severe nonsurvivable accident. Frequently the flight pattern,
communications, in-flight breakup, or other conditions will lead the
investigator to suspect incapacitation.

Incapacitation may be brought about by a number of conditions.
Medical conditions such as heart attacks, strokes, seizures, hypoglycemia,
etc., can lead to partial or complete incapacitation ana should always be
considered by the accident investigator. Any thorough investigation should
rule out significant preexisting disease. This is done by having an autopsy
performed. However, investigators must realize that the trauma to the
occupant in an aircraft accident may be of such a degree that the tissues
cannot be adequately examined; that the pathologist may do only a cursory
and thus incomplete examination on a highly traumatiz2d or burned body;
and that in many cases a thorough: examination may fail to reveal an
incapacitating condition--a condition that can only be indicated by a
thorough medical history. This is illustrated by a personal experience.

A 30-year-old man was stunt flyirg, practicing for an air show. He
broke off a maneuver at about 2,500 feet. The aircraft descended and struck
the ground at a 35° angle; the aircraft was demolished, and the pilot was
killed. The accident investigator at the scene told me that if the pilot was
not incapacitated he did not know whether or not he would be able to explain
the accident. A thorough autopsy on a relatively intact body failed to
reveal significant disease. Thus, the autopsy was negative in terms of
revealing any conditions that may have been incapacitating. On the other
hand, crash injury investigators, on questioning a number of persons who knew
the pilot, found that he had had trouble when trying to keep up a jogging program,

*Paper presented at the Fourteenth Annual Southern Methodist University Air
Law Symposium, Dallas, Texas, March 6-8, 1980.

**average figures calculated by the authors from NTSB Aircraft Accident
Reports, U.S. Civil Aviation, 1970 through 1975.

1

For

sior

—
yess



Technical Report Documentation Pege
a. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

FAA-AM-89- 6 | tL Al (esd 7 LID -

4. Title end Subtitle Report Date...
Medical and Toxicological Factors in A APRawDS
Aj aircrast Aecidents 7 me Performing Organization Code

le Performing Organization Report No.

— | —aushadal ——————
>, |i William R. }/Rirkham ;

9. Performing Organizetien Nome and Address. 10. Work Unit No. (TRAIS)
FAA Civil Aeromedical Institute
P.O. Box 25082 TI. Contract or Grant No.

Oklahoma City, Oklahoma 73125

12. Sponsoring Agency Nome ond Address
Office of Aviation Medicine
Federal Aviation Administration
300 Independence Avenue, S.W.
Washington, D.C. 20591

15. Supplementary Notes

Research leading to preparation of this report was performed under

Task AM-B-80-TOX-23.
a[ 76 Abstrect
“>tA number of factors operating within pilots may impair their ability to operate
aircraft in a safe manner, thus accounting for some of the 83 to 87 percent of
pilot "causes" of general aviaticn accidents. Aircraft accident investigators
should Le attuned to characteristics cf the accident, witness statements, and autopsy
and laboratory findings that may suggest partial or complete incapacitation in
the pilot. Incapacitation may be brought on by a medical condition which may be
revealed at autopsy or be inferred only from medical history. Spatial disorienta-
tion is a subjective evaluation only and a form of incapacitation rated as the
third most frequent “cause” of facal general aviation accidents. Lack of oxygen--
hypoxia--is a constant threat to incapacitate in aircraft operating at high alti-
tudes. Toxicological factors such as alcohol, drugs, and gases (e.g., carbon
Imonexide) should always be sought in fatal aircraft accidents by obtaining blood,
urine and other specimens for laboratory analyses. Aerial application pilots may
ibe incapacitated by the poisonous materials they apply, especialiy the cholinesterase-
inhibiting insecticides. The finding of therapeutic drugs in the blood or other
specimens from accident victims, or of tablets, pills, etc., at the scene, may
point to underlying medical conditions that may impair pilot performance. ‘The 5
author discusses these principles and illustrates them briefly with cases to make “
accident investigators and others aware of the importance of medical and toxicological] .
factors in aircraft seca

17. Key Words 18. Diswibution Stetement
Human factors Document is available to the public through
Medical factors the National Technical Information Service,
Toxicological factors Springfield, Virginia 22161 4
Aircraft accidents :
19. Security Clessif. (of this repert) D. Security Clessit. (of this pege) 21. Ne. of Poses | 22. Price

Unclassified Unciassified 9
Form DOT F 1700.7 (¢~72) Reproduction of completed poge outherized u

Abf-32c Ul



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