What is HYPOXIA? (AIM §8-2)
Hypoxia is a state of OXYGEN deficiency in the body sufficient to impair functions of the brain and other organs.
Cabin depressurization effects on human physiology
Carbon dioxide and water vapor pressure affect alveolar Oxygen.
Mean Sea Level - MSL
IN ALVEOLI (in the Lungs)
29000 Flight Level
39000 Flight Level
49000 Flight Level
Suppose we would be able to make flight on Flight Level 29000 feet without PRESSURIZATION.(somewhat near Everest top)
Remaining pressure is 172 mm Hg
(whether there were no other Oxygen application)
We would only get one fifth of Oxygen pressure for the bloodstream (34.4 mm Hg) instead of 104 mm Hg at Mean Sea Level.
What is hyperventilation? (AIM §8-2)
It is an abnormal increase in the volume of air brethed in and out of the lungs. It can occur subconsciously when a stressful situation is encountered in flight. This results in a significant decrease in the Carbon dioxide content of the blood. Carbon dioxide, of course, is needed to automatically regulate the breathing process.
Alcohol and Drugs
Histotoxic Hypoxia can be induced by the introduction of substances like alcohol or Drugs into tissue, reducing its ability to accept OXIGEN from bloodstream.
Anaemic Hypoxia is a reult of the blood being unable to carry OXYGEN, e.g. caused by exposure to Carbon MONOxide.
When a pilot take only carbohydrate in her/his diet the Respiratory Quotient is 1.00.
Stagnant Hypoxia results from the body's inability to carry OXIGEN to the BRAIN, which can result from high-gravity forces causing blood to pool in the lower extremities of the body.
Time of Safe Unconsciousness
Some experts believe that for passengers - in contradiction to the crew - a short period of unconsciousness during cabin depressurization can be tolerated since they are not performing an operational task. Unconsciousness is a clear sign of insufficient OXIGEN supply to the BRAIN and it is obvious that this time can only be very short before permanent brain demage occurs.
It is believed that a safe time of unconsciousness is somewhere between 90 seconds and 4 minutes.
Time of Uncounsciousness
Very large numbers of aircrew and passengers have been exposed to breathing air at cabin altitudes up to 8000 feet over the last 60 years cithout significant deleterious effect. Although exposure to this altitude reduces the OXYGEN partial pressure in the pulmonary tract the tissues of the body are maintained well above the required level.
Carbon MONOxide has a 240-times greater tendency than Oxygen to attach red blood haemoglobin, thus inactivating a large amount of haemoglobin as an Oxigen carrier.
Any delay in donning a mask will significantly increase the risck of losing consciousness.