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A sinus 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

sinus openings. Oral decongestants have side effects that can impair
pilot performance.

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

d.  Decompression Sickness After Scuba Diving.

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, altitude
decompression sickness due to evolved nitrogen

gas can occur during exposure to reduced barometric pressure (i.e., low
cabin pressure) associated with increased

altitude and may lead to a serious inflight emergency.

The recommended wait time before going to flight altitudes up to 8,000
feet is at least 12 hours after

diving that did not require a controlled ascent (i.e., non

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decompression stop diving), and at least 24 hours after

diving that required a controlled ascent (i.e., decompression stop
diving). The recommended wait time before

going to flight altitudes above 8,000 feet is at least 24 hours after
any SCUBA dive. These recommended altitudes

are actual flight altitudes above mean sea level (AMSL) and not
pressurized cabin altitudes. This takes into

consideration the risk of aircraft decompression during flight.

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3.  Hyperventilation in Flight

a.

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. As
hyperventilation "blows off" excessive

carbon dioxide from the body, a pilot can experience symptoms of
lightheadedness, suffocation, drowsiness,

tingling in the extremities, and coolness and react to them with even
greater hyperventilation. Incapacitation can

eventually result from incoordination, disorientation, and painful
muscle spasms. Finally, unconsciousness can

occur.

b.

The symptoms of hyperventilation subside within a few minutes after the
rate and depth of breathing are

consciously brought back under control. 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.

c.

Early symptoms of hyperventilation and hypoxire similar. Moreover,
hyperventilation and hypoxia can

occur at the same time. Therefore, if a pilot is using an oxygen system
when symptoms are experienced, the

oxygen regulator should immediately be set to deliver 100
percent oxygen, and then the system checked to assure

that it has been functioning effectively before giving attention to
rate and depth of breathing.

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4.  Carbon Monoxide Poisoning in Flight

a.

Carbon monoxide is a colorless, odorless, and tasteless gas contained
in exhaust fumes. When breathed

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.

b.

Most heaters in light aircraft work by air flowing over the manifold.
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.

c.

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, and
immediately shut off the heater and open

air vents. If symptoms are severe or continue after landing, medical
treatment should be sought.

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5.  Illusions in Flight

a.  Introduction.

Many different illusions can be experienced in flight. Some can lead to
 spatial

disorientation. Others can lead to landing errors. Illusions rank among
the most common factors cited as

contributing to fatal aircraft accidents.

Fitness for Flight

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