*7A Aeromedical Factors - Flight Physiology

Question 0

1. What is hypoxia?

AIM 8-1-2

Answer 0

Hypoxia is a state of oxygen deficiency in the body sufficient to impair functions of the brain and other organs.

Question 1

2. Where does hypoxia usually occur, and what symptoms should one expect?
   (AIM 8-1-2)

Answer 1

Although a deterioration in night vision occurs at a cabin pressure altitude as low as 5,000 feet, other significant effects of altitude hypoxia usually do not occur in the normal healthy pilot below 12,000 feet. From 12,000 feet to 15,000 feet of altitude, judgment, memory, alertness, coordination, and ability to make calculations are impaired, and headache, drowsiness, dizziness and either a sense of well-being or belligerence occur. Effects are worse above 15,000 feet.

Question 2

3. What factors can make a pilot more susceptible to hypoxia?
   (AIM 8-1-2)

Answer 2

The altitude at which significant effects of hypoxia occur can be lowered by a number of factors. Carbon monoxide inhaled in smoking or from exhaust fumes, lowered hemoglobin (anemia), and certain medications can reduce the oxygen-carrying capacity of the blood. Small amounts of alcohol and low doses of certain drugs, such as antihistamines, tranquilizers, sedatives, and analgesics can, through their depressant action, render the brain much more susceptible to hypoxia. Extreme heat and cold, fever, and anxiety increase the body’s demand for oxygen, and hence its susceptibility to hypoxia.

Question 3

4. How can hypoxia be avoided?

AIM 8-1-2

Answer 3

Hypoxia is prevented by heeding factors that reduce tolerance to altitude, by enriching the inspired air with oxygen from an appropriate oxygen system, and by maintaining a comfortable, safe cabin pressure altitude. For optimum protection, pilots are encouraged to use supplemental oxygen above 10,000 feet during the day, and above 5,000 feet at night.

Question 4

5. What is hyperventilation?

AIM 8-1-3

Answer 4

Hyperventilation, or an abnormal increase in the volume of air breathed in and out of the lungs, can occur subconsciously when a stressful situation is encountered in flight. This results in a significant decrease in the carbon dioxide content of the blood. Carbon dioxide is needed to automatically regulate the breathing process.

Question 5

6. What symptoms can a pilot expect from hyperventilation?

AIM 8-1-3

Answer 5

As hyperventilation “blows off” excessive carbon dioxide from the body, a pilot can experience symptoms of light-headedness, suffocation, drowsiness, tingling in the extremities, and coolness, and react to them with even greater hyperventilation. Incapacitation can eventually result from uncoordination, disorientation, and painful muscle spasms. Finally, unconsciousness can occur.

Question 6

7. How can a hyperventilating condition be reversed?

AIM 8-1-3

Answer 6

The symptoms of hyperventilation subside within a few minutes after the rate and depth of breathing are consciously brought back to normal. The buildup of carbon dioxide in the body can be hastened by controlled breathing in and out of a paper bag held over the nose and mouth.

Question 7

8. What is carbon monoxide poisoning?

AIM 8-1-4

Answer 7

Carbon monoxide is a colorless, odorless and tasteless gas contained in exhaust fumes. When inhaled, even in minute quantities over a period of time, it can significantly reduce the ability of the blood to carry oxygen. Consequently, effects of hypoxia occur.

Question 8

9. How does carbon monoxide poisoning occur, and what symptoms should a pilot be alert for?
   (AIM 8-1-4)

Answer 8

Most heaters in light aircraft work by air flowing over the manifold. The use of these heaters while exhaust fumes are escaping through manifold cracks and seals is responsible every year for several nonfatal and fatal aircraft accidents from carbon monoxide poisoning. A pilot who detects the odor of exhaust or experiences symptoms of headache, drowsiness, or dizziness while using the heater should suspect carbon monoxide poisoning.

Question 9

10. What action should be taken if a pilot suspects carbon monoxide poisoning?
    (AIM 8-1-4)

Answer 9

A pilot who suspects this condition to exist should immediately shut off the heater and open all air vents. If symptoms are severe, or continue after landing, medical treatment should be sought.

Question 10

11. What is the cause of motion sickness, and what are its symptoms?
    (FAA-H-8083-25)

Answer 10

Motion sickness, or airsickness, is caused by the brain receiving conflicting messages about the state of the body. Symptoms of motion sickness include general discomfort, nausea, dizziness, paleness, sweating, and vomiting.

Question 11

12. What action should be taken if a pilot or his passenger suffers from motion sickness?
    (FAA-H-8083-25)

Answer 11

If suffering from airsickness while piloting an aircraft, open up the air vents, loosen the clothing, use supplemental oxygen, and keep the eyes on a point outside the airplane. Avoid unnecessary head movements. Terminate the flight and land as soon as possible.

Question 12

13. What is “ear block”?

AIM 8-1-2

Answer 12

As the aircraft cabin pressure decreases during ascent, the expanding air in the middle ear pushes the Eustachian tube open. The air then escapes down to the nasal passages and equalizes in pressure with the cabin pressure. But during descent, the pilot must periodically open the Eustachian tube to equalize pressure. Either an upper respiratory infection, such as a cold or sore throat, or a nasal allergic condition can produce enough congestion around the Eustachian tube to make equalization difficult. Consequently, the difference in pressure between the middle ear and aircraft cabin can build to a level that will hold the Eustachian tube closed, making equalization difficult if not impossible. An ear block produces severe pain and loss of hearing that can last from several hours to several days.

Question 13

14. What action can be taken to prevent ear block from occurring in flight?
    (AIM 8-1-2)

Answer 13

Normally this can be accomplished by swallowing, yawning, tensing muscles in the throat or, if these do not work, by the combination of closing the mouth, pinching the nose closed and attempting to blow through the nostrils (Valsalva maneuver). It is also prevented by not flying with an upper respiratory infection or nasal allergic condition.

Question 14

15. What regulations apply and what common sense should prevail concerning the use of alcohol?
    (14 CFR 91.17, AIM 8-1-1)

Answer 14

The regulations prohibit pilots from performing crewmember duties within 8 hours after drinking any alcoholic beverage, while under the influence of alcohol, or having .04 percent weight or more alcohol in the blood. Due to the slow destruction of alcohol in the bloodstream, a pilot may still be under influence, or over the .04 percent mark, 8 hours after drinking a moderate amount of alcohol. Therefore, an excellent rule is to allow at least 12 to 24 hours from “bottle to throttle,” depending on the amount of alcoholic beverage consumed.

Question 15

16. What regulations apply and what common sense should prevail concerning the use of drugs and medication?
    (AIM 8-1-1)

Answer 15

Pilot performance can be seriously degraded by both prescribed and over-the-counter medications, as well as by the medical conditions for which they are taken. The regulations prohibit pilots from performing crewmember duties while using any medication that affects the faculties in any way contrary to safety. The safest rule is not to fly as a crewmember while taking any medication, unless approved to do so by the FAA.

Question 16

17. Discuss the effects of nitrogen excesses during scuba diving upon a pilot or passenger in flight.
    (AIM 8-1-2)

Answer 16

A pilot or passenger who intends to fly after scuba diving should allow the body sufficient time to rid itself of excess nitrogen absorbed during diving. If not, decompression sickness due to evolved gas can occur during exposure to low altitude and create a serious inflight emergency. The recommended waiting times before flight are as follows:
Flight altitudes up to 8,000 feet:
• Wait at least 12 hours after diving which has not required a controlled ascent.
• Wait at least 24 hours after diving which has required controlled ascent.
Flight altitudes above 8,000 feet:
• Wait at least 24 hours after any scuba dive.
Note: The recommended altitudes are actual flight altitudes above mean sea level and not pressurized cabin altitudes. This takes into consideration the risk of decompression of the aircraft during flight.