TYPES OF HYPOXIA


Anything that impedes the arrival or utilization of oxygen to the cell, places the body in whats called a hypoxic state. Hypoxia can effect any of 4 specific areas causing symptoms.


Location of Impediment Lungs Common Name Hypoxic Hypoxia Explanation Hypoxic hypoxia — not enough oxygen enters the body.


Any condition that interrupts the flow of O2 into the lungs. This is the type of hypoxia encountered at altitude due to the reduction of the partial pressure of O2.


Hypemic hypoxia — the blood cannot carry enough oxygen. Blood Hypemic Hypoxia


Any condition that interferes with the ability of the blood to carry oxygen. Anemia and carbon monoxide poisoning are two conditions that can keep the O2 from attaching to the hemoglobin within the red blood cell.


Stagnant hypoxia — there is not enough blood flow to deliver sufficient oxygen.


Blood Transport Stagnant Hypoxia


Any condition that interferes with the normal circulation of the blood arriving to the cells. Heart failure, shock, and positive G force along the Z axis will bring about this condition.


Histotoxic hypoxia — oxygen is delivered to cells, but the cells cannot use it.


Cell Histotoxic Hypoxia


Any condition that interferes with the normal utilization of O2 in the cell. Alcohol, narcotics and cyanide all can interfere with the cell's ability to use the oxygen in support of metabolism.


From the table, it is plain to see that any condition that interferes with oxygen’s normal path to the cells will bring on hypoxia. While all cells require oxygen to function, some cells require more oxygen than others. Most cells have the ability to store an emergency supply of O2. The central nervous system (made up of the brain and spinal cord) do not have this ability and also demand a great deal of oxygen (approximately 20% of all oxygen that you inhale feeds the brain). So, if the oxygen supply to the body is reduced, the brain will be one of the first organs to be affected. Another problem is that when the brain starts to feel the effects of hypoxia, the higher reasoning portion of the brain is the first affected. This means that judgment and cognitive skills diminish from the very start.


WARNING: A common misconception among pilots is that it is easy to recognize the symptoms of hypoxia and to take corrective action before becoming seriously impaired. While this concept may be appealing in theory, it is both misleading and dangerous for crewmembers.


Of all the symptoms, euphoria (a false sense of well-being) is probably the most dangerous. Furthermore, in most cases, hypoxia onset is very insidious. Any preoccupation with flying duties could be enough of a distraction to allow the hypoxia to progress beyond the point of self-help.


SEEING WELL AT NIGHT


At night, our eyes require more oxygen to function. Hypoxia is a condition where the body lacks sufficient oxygen, and its effects become more pronounced as altitude increases. At night, the given altitude at which a person could experience symptoms of hypoxia – including difficulty breathing, anxiety, headache, lack of awareness, or even unconsciousness – decreases. Pressurized airplanes mitigate this by maintaining a constant cabin altitude as the plane climbs or descends. However, pilots of all aircraft types must be aware of the physiological impacts of night flying.


High Altitude Awareness Training 14


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