Question of the Day

The Aerospace Medical Association is dedicated to the science of Aerospace Medicine.  The following questions and answers offer those interested in Aerospace Medicine activities the opportunity to test and expand your Aerospace Medicine knowledge.

Question: The key to survival is adjustment. The most difficult problems that a survivor will have in trying to adjust will be to overcome:

a. food aversions.
b. thirst hunger.
c. physical problems.
d. mental problems.
e. personality conflicts.
Answer: d. When you find yourself in a survival situation, there are several facts which you should remember. First of all, the obstacles you have to overcome aren't so much natural ones as they are mental ones. Remembering that people have gone to these places intentionally and even live there, survival is physically possible. By meeting your physical needs, many of the psychological problems will be overcome due to a positive mental attitude and self-confidence. Your problem is recognizing the mental problems which are also affecting you. REFERENCES: US Air Force. Air Force Manual 64-3. Survival Training Edition. Washington DC: US Government Printing Office, Department of the Air Force, 1969 Aug 15.

Question: Spatial disorientation is a significant contributor to Class A aircraft mishaps.

a. True.
b. False.
Answer: a. True. REFERENCE: US Air Force. USAF Safety Center Annual reports: 1995-1996.

Question: The primary hazards of space flight are:

a. decompression hazards.
b. impact hazards.
c. radiation hazards.
d. medical hazards.
e. microgravity hazards.
Answer: c. Three basic sources of naturally occurring space radiation can be hazardous to manned space flight-the magnetically trapped proton and electron environment (Van Allen belts), galactic cosmic radiation (extremely ionized nuclei, ranging from hydrogen to uranium; these nuclei originating outside the solar system), and solar particulate radiation (high energy particles, mostly protons, ejected from the sun). REFERENCES: Davis JR. Medical Issues for a Mission to Mars. Texas Med 1998 Feb;94(2):47-55.

Question: When considering non-ionizing radiation, one should include both natural and man-made sources. The major natural source of non-ionizing radiation is:

a. galactic
b. solar
c. terrestrial
d. galactic and solar.
Answer: c. The natural sources of non-ionizing radiation are galactic, solar, and terrestrial. Detectable components of extraterrestrial sources at non-ionizing frequencies are extremely weak. Even the sun cannot be considered a strong source of energy in this spectral region as the solar flux on earth generally does not exceed about 1mW-m-1. This is in contrast to natural electromagnetic fields of terrestrial origin from DC at about 3 kHz. REFERENCES: Adey WR. Tissue Interactions with Nonionizing Electromagnetic Fields. Physiological Review 1981;61:435-514.

Question: Which statement concerning vibration is true?

a. Ejection seat systems which are aerodynamically designed to seek their stable point may subject the rider to oscillations of from 3-10 Hz but their relatively small oscillatory magnitude will cause little harm.
b. Flight designed to follow the terrain contours often produces vibrations in the range between 3-10 Hz which is significant in causing motion sickness.
c. Flight at low altitude and high speed will produce motion sickness due to the greater exposure of these flights to adverse weather and gust effects of 0.01-0.1 Hz.
d. Helicopter vibrations consisting of 3-112 Hz from main rotor blades and 20-25 Hz from the tail rotor blade can cause problems in the areas of vision, speech and performance decrement.
Answer: d. Escape systems which seek a stable point in the airstream are commonly in the range of 3-10 Hz and 10-30of rotation. These large magnitudes of oscillation in self-stabilizing ejection seats are very significant in causing flail injuries to the extremities. Terrain following produces vibrations between 0.01 and 0.1 Hz (not 3-10 Hz) which is significant in causing interferences with vision, speech, disturbances in respiration and the musculoskeletal system. REFERENCES: US Navy. US Naval Flight Surgeon's Manual, 2nd ed. Washington DC: US Government Printing Office, Department of the Navy, 1978:2-14.

Question: An attempt was made to measure the effects of ethyl alcohol on vision. This was done by placing electrodes in thalamic visual areas of pigeon brains. The study revealed:

a. it is impossible to measure individual cell function in a pigeon's thalamus.
b. alcohol above 0.4 mg/kg killed the pigeons.
c. alcohol levels of 0.05 mg/kg had no effect on the pigeons.
d. small doses of alcohol exert differential effects on discrete portions of the brain which affect vision.
e. doses of alcohol above 0.4 mg/kg were required to completely block spontaneous
Answer: d. The experiment was successful and revealed that extremely small doses of ethyl alcohol in the range 0.05 mg/kg impair vision through its effects on information transfer in the colliculi-cortical visual projection system. One would expect a variety of subtle and complex effects on visual functions that are a function of dose. This is especially critical to aviation safety since the threshold levels are in a range substantially below levels currently believed "safe", e.g. 0.005%, 5 mg %, or 0.3-0.4 ounces of whisky in a 70 kg person. REFERENCES: Federal Aviation Administration, Washington DC: US Government Printing Office, US Department of Transportation, Office of Aviation Medicine Report No. FAA-AM-78-2.

Question: Breathing gas supplied via diluter demand regulators set to NORMAL (not "100% oxygen") at a cabin altitude of 22,500 ft provides:

a. sufficient oxygen to preclude symptoms of hypoxia at that altitude.
b. insufficient oxygen to preclude hypoxia immediately following rapid decompression 40,000 ft.
c. as much as 40% nitrogen, negating efficient denitrogenation.
d. all of the above.
e. none of the above.
Answer: d. (a)-(c) are all correct because the hypoxia-preventive addition of about 30% oxygen to ambient air at 22,500 ft reduces the alveolar oxygen tension slightly, albeit not enough to cause clinical hypoxia. However, a rapid decompression to 40,000 ft while breathing that mixture would result in clinical, potentially severe, hypoxia. The breathing mixture delivered by a diluter demand regulator set to NORMAL (mixed gas) will result in slower denitrogenation leading to greater potential for decompression sickness. REFERENCES: Ernsting J, King P, eds. Aviation Medicine. London: Butterworths, 1988:738. Webb JT, Balldin UI, Pilmanis AA. Prevention of Decompression Sickness in Current and Future Fighter Aircraft. Aviat Space Environ Med 1993;64:1048-50. Webb JT, Pilmanis AA. Breathing Gas of 100% Oxygen Compared with 50% Oxygen:50% Nitrogen Reduces Altitude-Induced Venous Gas Emboli. Aviat Space Environ Med 1993;64:808-12

Question: When a person hyperventilates at altitude:

a. the blood pH increases.
b. the respiratory quotient is driven below 1.
c. the kidney will retain bicarbonate.
d. carbonic acid levels fall faster than carbon dioxide levels.
e. all of the above
Answer: a. When a person hyperventilates, carbon dioxide is blown off reducing the carbon dioxide tension. This leads to a respiratory alkalosis which increases the blood pH. Because carbon dioxide is exhaled in large amounts and oxygen consumption does not increase a great deal, the respiratory quotient will be driven above 1 rather than below. A decrease in carbon dioxide tension occurs at a faster rate than a drop of carbonic acid-levels also causing a rise in blood pH. REFERENCES: Holmstrom FMG. Hypoxia. In: Randel HL, ed. Aerospace Medicine, 2nd ed. Baltimore: Williams & Wilkins, 1971:61.

Question: The beneficial in vivo effect of Hyperbaric Oxygen Therapy in the treatment of gas gangrene is that:

a. O2 is bacteriocidal for Clostridial organisms at tensions of 250mmHg.
b. O2 is bacteriostatic for Clostridial organisms, at tensions above 1400mmHg.
c. O2 stops alpha toxin production by Clostridial organisms at tensions of 250mmHg.
d. O2 stops alpha toxin production by Clostridial organism at tensions above 1400mmHg.
Answer: c. An O2 tension above 1400mmHg will kill Clostridial organisms. However, in vivo, in the region of the Clostridial phlegmon the O2 tension does not achieve this bacteriocidal level during treatment with 100% O2 at 3 times sea level pressure. Measured tissue O2 levels in these regions have been 400-600mmHg. However, O2 tensions of 250mmHg stop alpha toxin production. Circulating alpha toxin is detoxified by the body (not the O2) within an hour of its elaboration. Thus, when toxin production by the organism is stopped a rapid clinical improvement in the patient's condition ensues. REFERENCES Heimbach RD, Boerema I, Brummelkamp WH, Wolfe WG. In: Davis JC, Hunt TK, ed. Hyperbaric Oxygen Therapy. Bethesda: Undersea Medical Society, 1977:Ch 12. Kaye D. Effect of Hyperbaric Oxygen in Clostridia In Vitro and In Vivo. Proc Soc Exp Biol Med 1967;124:360. VanUnnik AJM. Inhibition of Toxin Production in Clostridium Perfringens In Vitro By Hyperbaric Oxygen. Antonie von Leeuwenhock 1965, 31:181.

Question: Studies of aircraft accidents over the past several decades consistently lists "pilot error" as the cause in about 70 percent of the accidents. The best approach to improving this situation should be based on which of the following premise?

a. Pilots continue to do things incorrectly. Additional training on flight procedures and the operation of aircraft systems is required.
b. Flight training should put increased emphasis on topics such as attention and motivation.
c. Accident rates will only decrease when all aircraft have cockpit voice recorders and video systems so pilot actions during an accident sequence can be studied in depth.
d. Selection procedures for aviation personnel must be continually improved to identify "error-prone" individuals prior to their entering flight training.
e. Pilots should be considered as one of many component of a total flight management system. Attention then should be given to the pilot's actions and to those system features (control design, information presentation, etc.) that might have led the pilot to improper action.
Answer: e. An accident generally is attributed to pilot error when no aircraft malfunction is noted and no obvious environmental feature (weather, etc.) appears to be at fault. However, when a well-trained and highly motivated individual has an accident, one should suspect that the accident may be "design-induced." In an airplane, the human is but one element in a complex system. He/she also is not an infallible element. The human operator may well be led to improper actions by misleading information presentations, by poor location of controls, by information overload, by competing system demands, and by other system-design issues. Nonetheless, the accident cause is listed as "pilot error. REFERENCES: Nagel DC. Human Error in Aviation Operations. In: Wiener EL, Nagel DC. Human Factors in Aviation. San Diego: Academic Press, 1988:263-303.

Question: An individual who has had a previous cold injury has _________ susceptibility to a subsequent injury.

a. increased
b. decreased
c. no change in
d. none of the above
Answer: a. Recurrent first degree frostbite decreases peripheral blood flow, increases cold sensitivity, and increases the risk of subsequent frostbite. REFERENCES: Pandolf KB, Sawka MN, Gonzalez RR, eds. Human Performance Physiology and Environmental Medicine at Terrestrial Extremes. Indianapolis: Benchmark Press, 1988. Sumner DS, Criblez TL, Doolittle WH. Host Factors in Human Frostbite. Military Med 1974;141:454-461. Wagstaff MA, Pethyridge RJ. Cold Injuries Norwegian Winter Deployment-85Great Britain: Institute of Naval Medicine, Alverstoke Hants, 1986, Report #20/86.

Question: Aircraft mishap and incident investigations are a key component in an aviation safety program because:

a. mishap investigations are usually simple and to the point.
b. maintenance error and material failures are the most frequent causal factors.
c. lessons learned provide a basis for prevention programs.
d. the flight surgeon or AME need investigate only the possible human factors involved.
e. mishaps are the primary method we have for determining safety needs or failures.
Answer: c. The flight surgeon or AME is charged with investigating the medical and human factor aspects of a mishap, unless a human factors specialist is specifically assigned. Most aircraft mishap investigations are difficult, time consuming and stressful for all concerned; especially since human error (most frequently pilot error) is the primary cause of most mishaps. Safety and mishap investigations must be thorough and complete, since they provide the basis for not repeating past errors. Aircraft mishaps and incidents frequently alert us to failures in our safety programs, but we strive to avert mishaps before they occur. A mishap or an incident too frequently indicates a failed or flawed safety program. REFERENCES: Crowley JS, ed. United States Army Aviation Medicine Handbook, 3rd ed. Ft Rucker: Society of United States Army Flight Surgeons, 1993:488.

Question: Fatigue is a threat to flying safety because it can cause performance decrement. All of the following are true of fatigue EXCEPT:

a. There are several tests, e.g. urinary catecholamines, 17-ketosteroids, which will reliably measure degree of fatigue and the point of onset of performance decrement.
b. To lessen the risk of fatigue, the major airlines restrict aircrew to only flying 80-120 hours per 30-day period.
c. Fatigue may cause a rise in sed rate, decreased leukocyte and eosinophil count, and an increased polymorphonuclear leukocyte count.
d. With fatigue, there is usually a decrease in blood pressure, increase in pulse, and a decreased pulse pressure.
e. As one becomes fatigued, increasing heterophoria may occur.
Answer: a. Although much is written about fatigue in the literature, its precise measurement remains obscure. Many laboratory and physiological aberrations, e.g., increased urinary catecholamines, decreased WBC count, and tendency for heterophoria have been noted in fatigue experiments. However, there is no proven correlation of these parameters with performance decrement. The issue is further clouded by inter and intra-individual variability. To illustrate the complexities, the fact that a pilot feels fatigued or tired does not necessarily mean his performance will suffer. On the contrary, some individuals may actually function more effectively if slightly fatigued. And at what point, for example, does the urinary catecholamine level or WBC count signal dangerous fatigue and performance decrement? Thus there are no known reproducible and reliable parameters to measure fatigue. Its presence and degree of task interference can best be determined by subjective complaints of the crewman as well as observation by other members of the crew. REFERENCES: Rayman RB. Cambodian Airlift. Aviat Space Environ Med 1977;48(5):460-464. Preston FS. Aircrew schedules. In: Aviation Medicine Health and Clinical Aspects. London: Tri-Med Ltd, 1978:40.

Question: Local fallout is defined as that radioactive material which is deposited on the earth's surface within 24 hours after detonation. Depending on many factors, the local fallout pattern can extend far beyond the area immediately affected by a nuclear detonation. This local fallout is worsened (intensified) as a result of:

a. a high altitude detonation, strong jet stream winds, thick cloud cover.
b. an air-burst (under 1,000 feet-fireball does not touch earth's surface),moderately strong surface winds, absent cloud cover.
c. a surface burst (fireball above and touching earth's surface), mild surface winds, heavy cloud cover with rain or snow.
d. a surface burst (fireball above and touching earth's surface), mild surface winds, absent cloud cover.
Answer: c. Fallout is formed from the weapon casing and electromechanical parts, unfissioned nuclear material and the fission products resulting from the chain reaction. These materials are instantly vaporized by the temperature of tens of millions of degrees present soon after detonation. In an air-burst or high altitude detonation, as soon as this temperature cools somewhat, the vaporized bomb materials condense into a very fine suspension of particles. These particles are drawn upward by the rapidly rising fireball and injected into the high altitude winds taking weeks, months and perhaps years to return to earth. A surface burst introduces much inert material from the earth's surface (soil, rocks and/or water) into the fireball. Secondary radiation is induced in some of this material by the flood of neutrons freed by the chain reaction. As the fireball cools, the radioactive portions of the weapon condense onto the surface material forming larger particles which fall to earth much faster and land closer to the point of detonation. Any factor which increases the speed with which these particles are returned to the surface will result in increased concentrations in the local area. Precipitation falling through the radioactive cloud will considerably worsen the fallout intensity in the local area. REFERENCES: US Air Force. NATO Handbook on the Medical Aspects of NBC Defensive Operations. Washington DC: US Government Printing Office, Department of the Air Force, AFR 161-3.

Question: Exercise prior to decompression:

a. increases incidence and severity of decompression sickness (DCS) during subsequent high altitude exposure.
b. can reduce incidence of DCS during subsequent high altitude exposure if performed during prebreathe.
c. increases the likelihood of hypoxia during subsequent high altitude exposure due to residual effects of increased metabolic rate.
d. has the same effect on incidence and severity of DCS as exercise performed during subsequent high altitude exposure.
e. has no effect on incidence and severity of DCS during subsequent high altitude exposure.
Answer: b. The exercise enhances perfusion and diffusion during prebreathing which facilitates removal of nitrogen. (a) is incorrect because research on humans has shown that exercise does not increase subsequent DCS susceptibility, even if breathing air at the time. (c) is incorrect because there is very little effect of exercise on cerebral metabolism following exercise. (d) is incorrect because exercise during exposure has been shown to increase incidence and severity of DCS (see a). REFERENCES: Webb JT, Fischer MD, Heaps CL, Pilmanis AA Exercise-Enhanced Preoxygenation Increases Protection from Decompression Sickness. Aviat Space Environ Med 1996;67:618-24. Balke B. Rate of Gaseous Nitrogen Elimination During Rest and Work in Relation to the Occurrence of Decompression Sickness at High Altitude. Randolph Field: US Air Force School of Aerospace Medicine. Project #21-1201-0014, Report #6. 1954:6. Webb JP, Ryder HW, Engel GL, Romano J, Blankenhorn MA, Ferris EB. The Effect on Susceptibility to Decompression Sickness of Preflight Oxygen Inhalation at Rest as Compared to Oxygen Inhalation During Strenuous Exercise. Comm Aviat Med Report #134, 1943:6

Question: In free fall at low altitude, a human body attains a velocity of:

a. 125 fps (85 mph) in 5 s in a distance of 400 ft.
b. 85 fps (125 mph) in 5 s in a distance of 400 ft.
c. 150 fps (102 mph) in 7 s in a distance of 700 ft.
d. 102 fps (150 mph) in 7 s in a distance of 700 ft.
e. a and c.
Answer: e. All of the numbers in answers (a) and (c) are correct for two points on the velocity-distance-time curve. Notice that they are 71% and 86% of terminal velocity, respectively, in only 5 s and 7 s. REFERENCES: Nuttall JB. Emergency Escape from Aircraft and Spacecraft. In: Randal HW, ed. Aerospace Medicine, 2nd ed. Baltimore: Williams and Wilkins, 1971:380.

Question: If a pilot wears rigid contact lenses, which is NOT an effect from flying:

a. dislodged lens from G forces and acceleration.
b. Bubbles under lens from altitude.
c. Dryness from low relative humidity.
d. Warpage from low humidity and low oxygen pressure.
Answer: d. Airmen with rigid lenses are more likely to develop centrally located bubble formation. Acceleration studies of hard contact lenses resulted in significant decentration with reduced vision. Flight crews who wear contact lenses inflight have complained of eye discomfort, which is most likely due to drying. Some aircraft have extremely low humidity. REFERENCES: Rayman RB. Ophthalmology. In: Rayman RB, ed. Clinical Aviation Medicine, 2nd ed. Philadelphia: Lea & Febiger, 1990:96.

Question: Aeromedical disposition of the head injured aviation personnel is based on:

a. absence of neurologic deficit- motor or sensory (vision, hearing) function.
b. absence of post traumatic syndrome.
c. acceptable risk of post traumatic epilepsy.
d. normal cognitive function.
e. all of the above.
Answer: e. Several factors are considered in the aeromedical disposition of head injured pilots. Prior to return to flight status, aviation personnel should be asymptomatic, without disqualifying defect, acceptable risk of post traumatic epilepsy, and normal cognitive function. Following mild head injury, patients often have vague neurologic sequelae. This has been termed the post traumatic syndrome or post concussive syndrome. Common symptoms of the post traumatic syndrome include headache, emotional liability, personality and mood changes, poor concentration, sleep disturbance, fatigue, imbalance, and disequilibrium. Aeromedical disqualifying conditions represent a risk to aeromedical safety. It is incumbent on the squadron Flight Surgeon to assess the flyer as soon as possible following a head injury to assist in potential aeromedical disposition problems. REFERENCES: Firth JL. Return to Flying After Head Injuries: A Review. Aviat Space Environ Med 1983; 54(7):603-608. Hughes JR. Posttraumatic Epilepsy in the Military. Military Med 1986;151(8):416-419. Lyons TJ, Katchen MS. Case #33 from the Aerospace Medicine Residents' Teaching File: An Aviator with head trauma and posttraumatic amnesia. Aviat Space Environ Med 1989; 60(10):1016-1017.

Question: You are seeing a 41 y/o Black loadmaster for his periodic short physical examination. He tells you that his father (70 y/o) recently died of cancer of the prostate and his older brother is undergoing an evaluation for prostate disease. He denies any voiding difficulties. You should (do):

a. a digital rectal exam (DRE) alone
b. a Prostatic Specific Antigen (PSA) test alone
c. counsel the patient regarding options a and b and offer both to him.
d. defer any evaluation until his next long physical examination.
e. send a consultation to your local urologist.
Answer: c. REFERENCES: Babaian J, et al. The Distribution of Prostate Specific Antigen in Men Without Clinical or Pathological Evidence of Prostatic Cancer: Relationship to Gland Volume and Age. J Urology 1992 May;147:837-840. Osterling JE, et al. Serum Prostate Specific Antigen in a Community Based Population of Healthy Men: Establishment of Age Specific Reference Ranges. JAMA 1993 Aug 18;270: 860-864. Catalona WJ, et al. Detection of Organ-Confined Prostatic Cancer is Increased Through Prostate-Specific Antigen-Based Screening. JAMA 1993 Aug 25;270: 948-954. Safford HR, et al. The Effect of Bicycle Riding on Serum Prostate Antigen Levels. J Urology 1996 Jul;156:103-105.

Question: You are a flight surgeon. During a routine flight physical exam you observe the weight of a pilot to be 175 lbs., and his height 69 inches. A quick formula to find out if he is overweight without looking at a chart is:

a. age + 15 Kg. x 2.2.
b. 106 lb. for the first 5 ft., then 6 lbs. for each additional inch.
c. 30.00 + 2035 x weight (kg.) - 0.375.
d. weight-lean body weight.
Answer: b. A quick and fairly accurate formula to find out a person's ideal weight (average or medium frame) is for a male: 106 lbs for the first 5 ft, then 6 lbs for each inch over 5 ft. For females: 100 lbs for the first 5 ft, then 5 lbs per inch. This formula will help greatly if no chart is available. REFERENCES: Williams SR. The Problem of Obesity and Weight Control. In: Nutrition and Diet Therapy, 3rd ed. 1977.

Question: The mechanism of the ear for converting the sound pressure waves from an air to a fluid medium without significant loss of energy is called impedance matching and this is done through:

a. rapid fatigue of the auditory nerves.
b. movement of the otoliths in the cochlear canals
c. size differential between the eardrum and the footplate of the stapes and the lever action of the ossicles.
d. the property of binaural hearing and that sound waves do not strike the ears at the same intensity
Answer: c. Only 1% of airborne sound enters the liquid medium whereas 99% is reflected away. The middle ear has two arrangements to narrow this potential energy loss. The first is the size differential between the eardrum and the footplate of the stapes. The eardrum has an effective area ratio which is 14 times greater than that of the stapedial footplate. This hydraulic effect increases the force pressure from the eardrum onto the footplate of the stapes so that there is approximately a 23 dB increase of sound intensity on the fluid of the inner ear. The second is the lever action of the ossicles amplifies the intensity of sound as it traverses the middle ear by about 2.5 dB. Thus, the impedance matching mechanism of the middle ear is not perfect, but accounts for 25.5 dB increase in the intensity of sound pressure at the air-liquid interface. REFERENCES: Antecaglia JR. The Industrial Environment-Its Evaluation and Control. Washington DC: US Government Printing Office, US Department of Health, Education, and Welfare, 1973:315.

Question: One of the most common electrocardiographic interpretations that must be made in evaluating aircrew members involves nonspecific T-wave changes. These may be indicative of which of the following?

a. Previous myocardial infarctions.
b. Failure of the subject to have properly maintained-the fasting basal state
c. Anxiety at the time of the electrocardiogram
d. all of the above
Answer: d. Nonspecific T-wave changes are very common and may be caused by any of a number of factors such as anxiety, apprehension, eating, drinking, cigarette smoking, and hyperventilation. A well maintained fasting basal state at the time of electrocardiogram will eliminate a significant portion of the abnormalities. A myocardial infarction must be ruled out if follow-up does not define a cause of the T-wave changes. REFERENCES: Lamb LE. Cardiopulmonary Aspects of Aerospace Medicine. In: Randel HW, ed. Aerospace Medicine, 2nd ed. Baltimore: Williams & Wilkins, 1971:505.

Question: In patients with chronic obstructive airway disease:

a. the safety of air transportation is improved if supplementary oxygen is available.
b. respiratory status may decline if 100% oxygen is given.
c. pulmonary function tests provide a useful indication of likely inflight problems
d. flight is contraindicated if there is dyspnea at rest.
e. all of the above are correct.
Answer: e. In patients with chronic bronchitis, emphysema, bronchiectasis, and cor pulmonale, where oxygenation is already compromised, exposure to altitude may result in severe tissue hypoxia. Most of these patients may be transported satisfactorily provided that supplementary oxygen is available during the flight. A ground level PO2 of 50 mmHg is a good indication that supplementary oxygen should be used. The use of 100% oxygen may, however, worsen some cases, since it may remove the hypoxic drive to ventilation, with consequent hypoventilation and carbon dioxide retention. In general, dyspnea at rest is a contraindication to flight, and patients with poor exercise tolerance (dyspnea after walking 50 m on level ground) require further assessment with full pulmonary function tests and a trial of 100% oxygen. Although a low pre-flight arterial PO2 level provides a useful pointer to likely in-flight problems, the additional use of pulmonary function tests, and particularly the FEV1, is even more valuable. REFERENCES: Fitness to Travel by Air. In: Harding RM, Mills FJ, eds. Aviation Medicine, 3rd ed. London: British Medical Journal, 1993:58-72.

Question: Concerning International Health Regulations (IHR), the following apply EXCEPT:

a. Most but not all countries are signatories.
b. Any required updating to the IHR is published in the Weekly Epidemiological Record of the WHO.
c. Diseases "subject to the Regulation" include plague, malaria, and yellow fever.
d. The WHO must be notified within 24 hours of the occurrence of any disease subject to the Regulation.
e. The IHR's serve as guidelines for countries to customize to meet their health needs.
Answer: c. Diseases subject to regulation are cholera, plague and yellow fever. Signatory countries have formal obligation to observe IHR guidelines, but are expected to expand on them to meet the unique health requirements of their countries. Any outbreak of cholera, plague or yellow fever requires notification of WHO within 24 hours. The Weekly Epidemiologic Record is the vehicle through which WHO notifies the international community of updates to the IHR's. REFERENCES: Ernsting J, King. Aviation Medicine, 2nd ed. London: Butterworths, 1988:518-521.

Question: You are involved in the investigation of a general aviation, light airplane crash. Your findings reveal that the crash forces were minimal, and certainly survivable, and yet the pilot received a fatal injury due to head trauma. You conclude that a shoulder restraint would have prevented this injury and recommend that all light aircraft built from this day on should be equipped with shoulder harnesses. How many years would it be before all aircraft would have shoulder restraints (what is the serviceable average life of general aviation aircraft already in the fleet)?

a. 5 years
b. 10 years
c. 15 years
d. 20 years
Answer: d. The average life of a general aviation light aircraft is estimated to be 20 years. Any safety recommendation that does not involve retrofitting existing aircraft, will take at least twenty years before its full impact will be realized. REFERENCES: Snyder RG. General Aviation Crash Survivability. Warrendale: Society of Automotive Engineers. Technical paper series #7800 17, 1978:3-12.

Question: What drug is useful in the prevention of Acute Mountain Sickness (AMS)?

a. Lasix
b. Nifedipine
c Dexamethasone
d. Acetazolamide
e. Oxygen
Answer: d. Acetazolamide has been shown to prevent the occurrence of AMS in some people. The usual dose is 125 mg qhs or BID for more severe cases. This can't be used in people allergic to sulfa drugs. Lasix will prevent the edema which is associated with high altitude exposure but does not affect AMS. Nifedipine is used in the prevention and treatment of HAPE, but again is not used for prevention of AMS. Dexamethasone is used to treat severe AMS and HACE. REFERENCES: Bezruchda S. Altitude Illness: Prevention and Treatment. Seattle: The Mountaineers. 1994:Table 3.

Question: When a pilot performs a -Gz maneuver immediately followed by a +Gz maneuver, the G level to cause unconsciousness during the +Gz maneuver is:

a. increased due to cardiovascular compensation mechanisms.
b. decreased due to cardiovascular compensation mechanisms.
c. unaffected due to cardiovascular compensation mechanisms.
d. independent of the eye-to-heart hydrostatic column height.
e. none of the above
Answer: b. Negative Gz has the effect of greatly increasing the blood pressure of the head and neck. As the pressure at the carotid sinus baroreceptor increases, the heart rate decreases and simultaneously decreases the peripheral resistance. Even a high rate of G offset to less than +1Gz can trigger the heart rate decrease. If the -Gz is held long enough the compensation mechanisms can return conditions close to normal, but this is usually not the case. When the -Gz event is immediately followed by a +Gz event, as in combat or aerobatics, the physiological state of low heart rate and decreased peripheral resistance put the pilot in exactly the wrong physiological position the handle +Gz. Consequently, the G level to cause unconsciousness during the +Gz maneuver is decreased. This phenomenon has been demonstrated in World War II aircraft, during aerobatic "vertical-8" maneuvers, and recently in modern combat aircraft with the effect called the "Push-Pull" effect. REFERENCES: Burton RR, Whinnery JE. Biodynamics: Sustained Acceleration. In: DeHart RL ed. Fundamentals of Aerospace Medicine. 2nd ed. Baltimore: Williams &Wilkins, 1996:201-260.

Question: Mustard gas produces eye injuries which are:

a. insidious with low concentrations.
b. associated with a latent period.
c. easily treated, judged by the experience of WW I.
d. a and b
e. all of the above
Answer: e. The eye is more sensitive and more vulnerable to mustard gas than any other part of the body. About 86% of the mustard casualties of WWI had eye lesions of some kind, but 75% of these were mild, with recovery in 1-2 weeks. Exposure for 2 hr to a concentration of mustard barely perceptible by odor (0.001 mg/L) will produce mild conjunctivitis after a latent period of 4-12 hr. REFERENCES: US Air Force. Treatment of Chemical Agent Casualties and Conventional Military Chemical Injuries. Bolling AFB: Office of the Surgeon General, Air Force Manual 160-12, 1974 May:4-2, 5-3.

Question: In handling the air evacuation of patients with orthopedic problems, which of the following actions is NOT necessary prior to evacuating the patient?

a. Hanging weight traction must be removed and replace with constant tension (Collins) spring traction.
b. Recently applied casts should be bivalved and taped in place.
c. Casts should be removed and replaced with firmly inflated air splints to prevent the vibration of the aircraft from causing abrasions and chafing and to aid in emergency evacuation of the aircraft, if necessary.
d. Patients with mandibular immobilization must have provision for rapidly removing the fixation, either with a "ripcord" device or with wire cutters at the bedside.
e. Patients soon after vascular repair should have their casts windowed over the site of the repair.
Answer: c. There is no necessity for removing casts if they are bivalved prior to flight. Even bivalved, the cast will provide better support than will an air splints, and air splints tend to get tighter with altitude, thus being more likely to cause circulatory embarrassment. (a). Acceleration and vibration can eliminate all benefits hopefully gained if weights are relied upon. A constant degree and direction of tension is necessary, and spring traction can provide it. (b). Bivalving and taping casts allows for swelling of the tissues both due to initial trauma and to altitude changes. Thus, it is not as necessary to pay close attention to the circulatory status of the extremity as would be the case with an air splint. Gas expansion in the GI tract can cause severe pain for a patient in a non-bivalved spica cast. In addition, bivalving the cast aids in evacuating the patient from the aircraft in case of emergency, such as fire or crash landing. (d). A means must be available to allow the patient to vomit in the event of airsickness. Otherwise, aspiration is a certainty. (e). Such windowing is vital both for observation and for treatment in the event of bleeding from the repair site. REFERENCES: Reddick E. Aeromedical Evacuation. Am Family Phys 1977;16(4):154-160. US Air Force. Aeromedical Evacuation Nursing. Washington DC: US Government Printing Office, Pamphlet 164-2 1976 Apr 2:10-1, 10-2. Hart RK. The Passenger and the Patient in Flight. In: DeHart RL ed, Fundamentals of Aerospace Medicine, 2nd ed, Baltimore: Williams & Wilkins, 1996.

Question: Each year, approximately 2 billion toys and games are sold in the US. During 1996, 13 toy-related deaths among children were reported to the US Consumer Product Safety Commission. It is estimated that 116,800 nonfatal injuries requiring emergency care also occurred. Which group is at highest risk for a toy-related injury?

a. girls, aged 5-9 years
b. boys, aged 0-4 years
c. girls, aged 10-14 years
d. boys, aged 15-19 years
e. girls, aged 15-19 years
Answer: b. Of the 116,800 estimated cases, 76,000 (65%) occurred in males. Fifty-six percent of the cases were in children aged 0-4, followed by 29% in the 5-9 age group, 10% among those aged 10-14, and 5% of those aged 15-19. Most injuries were lacerations (45%) followed by abrasions/contusions (21%), ingestion of a or lodging or a foreign body (12%), fractures or dislocations (7%), sprains/strains (5%) and miscellaneous injuries (10%). Approximately 2/3's occurred above the neck and involved the face (32%), head (15%), mouth (11%) and eye (5%). Fingers accounted for 5% of the injuries, and 1% of children required hospitalization after the event. REFERENCES: Toy-related Injuries Among Children and Teenagers-US 1996. MMWR 1997;46:1185-1189.

Question: Examples of primary prevention for cardiovascular disease include all of the following EXCEPT:

a. control of high blood pressure.
b. control of congestive heart failure.
c. control of high blood cholesterol.
d. increasing physical activity.
e. cessation of smoking.
Answer: b. Primary prevention is intervention PRIOR to the onset of disease in an effort to prevent disease onset. Therefore, control of risk factors, such as high blood pressure, high blood cholesterol, inactive lifestyle and the use of tobacco, is considered primary prevention for cardiovascular disease. Control of the symptoms of the disease, such as congestive heart failure, are examples of secondary prevention. REFERENCES: Simons-Morton DG, Cutler JA. Cardiovascular Disease Prevention Research at the National Heart, Lung and Blood Institute. Am J Prev Med 1998;14(4)317-330