AVIA 300: Trapped Gas & Evolved Gas in Humans

FAA Definition: Any volume of gas in a human body unable to equalize with ambient atmospheric pressures.
Gas can be trapped in various locations within the body.
The gas inside the body will expand and compress adhering to Boyle's Law.
- As the pressure on a gas increases, its volume decreases because the gas particles are forced closer together.

One of the most common problems during descent, often referred to as an 'ear block,' due to pressure equalization issues in the middle ear.
During ascent, the gas in the middle ear expands, forcing air down the Eustachian tube to equalize pressure, which causes pain.

Most common when transitioning from a relatively low-pressure environment to a higher-pressure one, typically during descent from altitude.
Can cause significant pain and potentially impair a pilot's ability to safely operate the aircraft or make rational decisions.
Treatment: Same as for blockages in the ears.

Occurs when an air pocket is present within a tooth.
As trapped gas expands in this confined space, it causes pain, creating a sensation that the tooth is being squeezed.
In-flight action: If tooth pain is experienced:
- Immediately descend.
- Identify the affected tooth.
- Seek a dentist upon landing.

During ascent to higher altitudes, gas within the gastrointestinal tract expands.
The GI tract is not designed for significant expansion, leading to discomfort or pain.
Treatments include:
- Passing gas.
- Avoiding gas-forming foods prior to flight.
- Stomach massage.
- Loosening restrictive clothing.

Normally, air in the lungs is passively expired during descent.
However, if descent is too rapid, the lung tissue can tear due to the volume of air and pressure differential in the lungs.
Rapid descent definition: A pressure differential of 10 psi or more within 0.1-0.5 seconds.

Gases are always present within the human body, and their expansion/compression consequences must be considered for every flight.
Major consequences with sinuses and ears typically do not occur below 10,000 ft.
Dental issues (barodontalgia) can manifest at any altitude.
GI tract issues (barotrauma) usually occur above FL180 (18,000 ft).
Prevention strategies:
- Avoid flying with an upper respiratory infection.
- Do not consume gas-forming foods before a flight.
- Maintain proper dental hygiene.

Caisson workers were the first to identify physical problems related to pressure changes, coining the term 'caisson disease.'
Deep-sea divers observed that the deeper they went, the greater the number and severity of Decompression Sickness (DCS) symptoms after ascent, while feeling better at depth.