Microlight » Human Factors » Barotrauma
Barotrauma is the trauma (pain) which can result from excessive differential pressure caused by barometric (pressure) changes.
There are certain areas in the human body which can contain gas. These are:
- Middle ear, behind the eardrum
- Tooth fillings
With an increase in altitude and the corresponding decrease in pressure, any trapped gas tends to expand. As the air pressure increases again when we come back toward earth, any gas that is trapped will tend to contract, and create a vacuum.
There will be an increase in pressure differential across the wall of whatever is trapping it and if it is large enough, can cause pain.
We can experience pain on the climb or the descent, but are more likely to experience pain in the middle ear and sinuses on the descent, and the sinuses and stomach in the climb.
The Eustachian Tube
The eustachian tube joins the middle ear to the back of the throat. Any gases in the middle ear can pass through the eustachian tube to the back of the throat, thus equalising the pressures.
A flap valve on the nasal end of the eustachian tube will open when ambient atmospheric pressure is decreasing (in a climb), but tends to remain closed with an increase in pressure (in the descent), therefore blocking the middle ear and causing the gas to be trapped.