Overview
Hypoxia is the state of oxygen deficiency in the body sufficient to impair functions of the brain and organs.
Symptoms may include headache, drowsiness, sense of well-being, belligerence, euphoria, blue fingernails, and blue lips. Especially above 12,000 feet MSL, judgment, memory, alertness, coordination, and ability to make calculations are impaired. It goes without saying that these are all capabilities required of a pilot. The importance of understanding what hypoxia is, what causes it, how to recognize, and how to correct it are critical for all pilots.
Commentary
The FAA has identified four specific types of hypoxia, each with different causes:
| Variation | Description |
|---|---|
| Hypoxic | Occurs as a result of insufficient oxygen available due to the reduction in partial pressure of oxygen at high altitudes. |
| Hypemic | Occurs when the blood is not able to take up and transport a sufficient amount of oxygen to the cells due to deficiencies in the blood itself. |
| Histotoxic | Occurs when the cells are not able to use the oxygen they receive due to the impairment of cellular respiration caused by alcohol or other drugs. |
| Stagnant | Occurs when oxygen-rich blood is not moving due to G-forces or a constricted artery. |
It's easy to measure the amount of oxygen in your blood using a pulse oximeter. This AvWeb article post includes a chart of normal ranges at different altitudes which can used as a guideline for using the pulse oximeter in the airplane. It's critical to be aware that a pulse oximeter cannot detect carbon monoxide poisoning. There's more about this in the aforementioned post.