Hypoxia Overview:
Sometimes called mountain sickness or altitude sickness, hypoxia is simply a lack of oxygen at the tissue level of the body due to a decreased partial pressure of oxygen in the inspired air. Hypoxia is serious, because it may lead to death.
A syndrome, anoxia, meaning literally "without oxygen," is occasionally and erroneously used to denote a deficiency, rather than a lack of oxygen in the tissues. This term is not used for flight below 55,000 feet. Even in acute cases the tissues are never entirely without oxygen.
The Cause of Hypoxia:
Hypoxia may be caused by climbing to an altitude where the body is susceptible to a loss of arterial oxygen below that required by the body.
Equipment failure, either a mechanical malfunction or exceeding the capabilities of the design, of a pressurized aircraft or a supplemental oxygen system, can lead to loss of arterial oxygen.
Hypoxia type:
Hypoxia poses a real danger to pilots. There are several types.
- Histotoxic Hypoxia – This form results from tissue
poisoning such as from alcohol, narcotics, and certain
poisons. The utilization of oxygen by the body tissues is
interfered with and the tissues are unable to metabolize
the delivered oxygen.
- Hypemic Hypoxia – The inability of oxygen to bind to the hemoglobin, as a result of a large blood loss, chronic
anemia (decreased hemoglobin content), or the forming of compounds with hemoglobin (carbon monoxide, nitrites,
sulfa drugs) that reduces the amount of hemoglobin available to form oxyhemoglobin.
- SMOKERS BEWARE: Carbon monoxide has an affinity
for the blood 20 times greater than oxygen. Given a choice between carbon monoxide and oxygen, the hemoglobin will choose the carbon monoxide. A regular smoker has a
physiologic altitude of 3,000 to 8,000 feet while at sea level.
- Hypoxic Hypoxia – This is a lack of oxygen as a result of
a high altitude (decreased oxygen pressure) or by conditions that prevent or interfere with the diffusion of oxygen across the
alveolar membrane (asthma, pneumonia, tumors, arterial
venous shunts).
- Stagnant Hypoxia – This is attributable to a malfunction
of the circulatory system resulting in a decrease in blood flow. Causes include high g-loading, exposure to extreme hot or
cold temperatures, or by shock.
Hypoxia Symptoms:
Hypoxia symptoms are diverse, varying from person to person, depending on variables such as absolute altitude, rate of ascent, duration at altitude, ambient temperature and physical activity.
Individual factors include: inherent tolerance, physical fitness, emotionality, and acclimatization.
It is felt that if a person has attended physiologic training and has determined his individual character for the onset of hypoxia, that character identify remains the same.
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