AIM 

4/20/23 

5. 

The effects of hypoxia are usually quite difficult to recognize, especially when they occur gradually. 

Since symptoms of hypoxia do not vary in an individual, the ability to recognize hypoxia can be greatly improved 

by experiencing and witnessing the effects of hypoxia during an altitude chamber “flight.” The FAA provides 

this opportunity through aviation physiology training, which is conducted at the FAA Civil Aeromedical Institute 

and at many military facilities across the U.S. To attend the Physiological Training Program at the Civil 

Aeromedical Institute, Mike Monroney Aeronautical Center, Oklahoma City, OK, contact by telephone (405) 

954

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6212, or by writing Aerospace Medical Education Division, AAM

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400, CAMI, Mike Monroney 

Aeronautical Center, P.O. Box 25082, Oklahoma City, OK 73125. 

NOTE

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To attend the physiological training program at one of the military installations having the training capability, an 

application form and a fee must be submitted. Full particulars about location, fees, scheduling procedures, course content, 

individual requirements, etc., are contained in the Physiological Training Application, Form Number AC 3150

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7, which 

is obtained by contacting the accident prevention specialist or the office forms manager in the nearest FAA office. 

6. 

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. The CFRs require that at the minimum, flight crew be provided with and use 

supplemental oxygen after 30 minutes of exposure to cabin pressure altitudes between 12,500 and 14,000 feet 

and immediately on exposure to cabin pressure altitudes above 14,000 feet. Every occupant of the aircraft must 

be provided with supplemental oxygen at cabin pressure altitudes above 15,000 feet. 

b.  Ear Block. 

1. 

As the aircraft cabin pressure decreases during ascent, the expanding air in the middle ear pushes the 

eustachian tube open, and by escaping down it to the nasal passages, equalizes in pressure with the cabin pressure. 

But during descent, the pilot must periodically open the eustachian tube to equalize pressure. This can be 

accomplished by swallowing, yawning, tensing muscles in the throat, or if these do not work, by a combination 

of closing the mouth, pinching the nose closed, and attempting to blow through the nostrils (Valsalva maneuver). 

2. 

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 up to a level that will hold the 

eustachian tube closed, making equalization difficult if not impossible. The problem is commonly referred to 

as an “ear block.” 

3. 

An ear block produces severe ear pain and loss of hearing that can last from several hours to several days. 

Rupture of the ear drum can occur in flight or after landing. Fluid can accumulate in the middle ear and become 

infected. 

4. 

An ear block is prevented by not flying with an upper respiratory infection or nasal allergic condition. 

Adequate protection is usually not provided by decongestant sprays or drops to reduce congestion around the 

eustachian tubes. Oral decongestants have side effects that can significantly impair pilot performance. 

5. 

If an ear block does not clear shortly after landing, a physician should be consulted. 

c.  Sinus Block. 

1. 

During ascent and descent, air pressure in the sinuses equalizes with the aircraft cabin pressure through 

small openings that connect the sinuses to the nasal passages. Either an upper respiratory infection, such as a cold 

or sinusitis, or a nasal allergic condition can produce enough congestion around an opening to slow equalization, 

and as the difference in pressure between the sinus and cabin mounts, eventually plug the opening. This “sinus 

block” occurs most frequently during descent. 

2. 

A sinus block can occur in the frontal sinuses, located above each eyebrow, or in the maxillary sinuses, 

located in each upper cheek. It will usually produce excruciating pain over the sinus area. A maxillary sinus block 

can also make the upper teeth ache. Bloody mucus may discharge from the nasal passages. 

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Fitness for Flight