RichOffDuty
08-21-2005, 07:15 AM
Because of the recent B737 accident in Greece, I thought it might be a good time to recap on Hypoxia.
Rich
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Hypoxia — It's not just for jet pilots
As Greek officials begin to unravel what caused the Sunday crash of a Helios Air Boeing 737, early reports seem to indicate that loss of cabin pressurization may be a factor. Greek Air Force pilots observed the 737 copilot wearing an oxygen mask but slumped over the controls. The passenger oxygen masks had deployed. And many of the bodies were reportedly found frozen, possibly indicating the jet's environmental control failed at altitude.
While the extremes at 30,000 feet are foreign to most general aviation aircraft, the issues are not as far removed from the typical single-engine pilot as you might think. Any time you fly above 10,000 feet (5,000 feet at night), you need to think about hypoxia — what effect diminished oxygen levels can have on you and your ability to fly the aircraft safely.
http://www.aopa.org/whatsnew/newsitems/2005/050815hypoxia.html
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HYPOXIA SIGNS AND SYMPTOMS
Because hypoxia is insidious and because the signs and symptoms are varied, the safest and most effective way to reduce your risk of becoming hypoxic is to attend a formal course in aviation physiology. Participating in an altitude chamber flight would give you the opportunity to experience hypoxia first hand; you would be able to experience your own symptoms, and would be able to observe the signs of hypoxia in the other class participants.
Pilots must understand that the signs and symptoms of hypoxia are as varied and individual as the person experiencing them. Pilots who are hypoxic will experience (most of the time) similar signs and symptoms. However, the signs and symptoms may appear in a different order and in varying intensities.
The greatest benefit in experiencing hypoxia signs and symptoms personally in the hypobaric (altitude) chamber during a high altitude-training course is that you will know what to look for while you are flying. This is important because your signs and symptoms of hypoxia will remain relatively constant throughout your flying career.
TIME OF USEFUL CONSCIOUSNESS (TUC) OR EFFECTIVE PERFORMANCE TIME (EPT)
These interchangeable terms describe the period of time between the interruption of the oxygen supply or exposure to an oxygen-poor environment and the time when a pilot is unable to perform flying duties effectively, such as putting on oxygen equipment or descending to a safe altitude. Table 2 shows the average TUC or EPT for various altitudes. The table is to be used as a guide only; the times are based on healthy individuals at rest in a hypobaric (altitude) chamber. One important fact to keep in mind is that following a rapid decompression to and above 30,000 feet, the average TUC/EPT will be reduced from 1/3 to 1/2 its original value. This is due to phenomenon known as reverse diffusion or fulminating hypoxia. This occurs when oxygen is forced out from the lungs due to the rapid expansion of gas during a rapid decompression. The result is acute and immediate hypoxia.
FACTORS INFLUENCING TOLERANCE TO HYPOXIA
It is impossible to predict exactly when, where, or how hypoxic reactions will occur in an individual pilot. The appearance and severity of the signs and symptoms are aggravated by several factors; rate of ascent, time spent at altitude, physical activity at altitude, fatigue, self-imposed stress, extreme ambient temperature, and individual physiological fitness.
PREVENTION OF HYPOXIA
There is nothing magic about preventing hypoxia; fly a well-maintained pressurized airplane or fly at an altitude where oxygen is not required. Obviously this is not always practical, and by following these simple guidelines you will be able to reduce your chances of experiencing hypoxia during flight. If pressurization is not an option and supplemental oxygen is not available, limit your exposure time to less than 1 hour between 10K feet and 14K feet, including not more than 30 minutes between 12K feet and 14K feet. If you have supplemental oxygen, use it above 5K feet during night flights and above 10K feet during daytime flights.
TREATMENT OF HYPOXIA
If hypoxia is suspected in yourself or others on board an aircraft, follow these simple steps:
*Check your equipment for proper operation
*Administer supplemental oxygen (don your oxygen mask)
*Ensure the regulator is turned on
*Check the flow indicator (this will tell you that something is coming to the mask)
*Monitor your breathing rate and depth (intentionally slow your breathing to prevent hyperventilation, use the flow indicator to help you monitor respiration)
*If safe, descend to an altitude (below 10K feet) where supplemental oxygen is no longer required
SOME FINAL THOUGHTS
Hypoxia is a constant and dangerous companion while flying. The insidious nature of hypoxia means that you must constantly be suspicious of how you and your passengers feel. Once hypoxia is recognized, quick and decisive action means recovery is only seconds away. The key, then, to flying safely at altitude is to be able to: identify the flight condition in which you may become hypoxic, recognize your personal hypoxia symptoms, and to recover from hypoxia before you have gone beyond your ability or desire to help yourself.
http://www.cami.jccbi.gov/aam-400/beware.htm
Rich
-------------------------------------------------------------
Hypoxia — It's not just for jet pilots
As Greek officials begin to unravel what caused the Sunday crash of a Helios Air Boeing 737, early reports seem to indicate that loss of cabin pressurization may be a factor. Greek Air Force pilots observed the 737 copilot wearing an oxygen mask but slumped over the controls. The passenger oxygen masks had deployed. And many of the bodies were reportedly found frozen, possibly indicating the jet's environmental control failed at altitude.
While the extremes at 30,000 feet are foreign to most general aviation aircraft, the issues are not as far removed from the typical single-engine pilot as you might think. Any time you fly above 10,000 feet (5,000 feet at night), you need to think about hypoxia — what effect diminished oxygen levels can have on you and your ability to fly the aircraft safely.
http://www.aopa.org/whatsnew/newsitems/2005/050815hypoxia.html
--------------------------------------------------------------------------------
HYPOXIA SIGNS AND SYMPTOMS
Because hypoxia is insidious and because the signs and symptoms are varied, the safest and most effective way to reduce your risk of becoming hypoxic is to attend a formal course in aviation physiology. Participating in an altitude chamber flight would give you the opportunity to experience hypoxia first hand; you would be able to experience your own symptoms, and would be able to observe the signs of hypoxia in the other class participants.
Pilots must understand that the signs and symptoms of hypoxia are as varied and individual as the person experiencing them. Pilots who are hypoxic will experience (most of the time) similar signs and symptoms. However, the signs and symptoms may appear in a different order and in varying intensities.
The greatest benefit in experiencing hypoxia signs and symptoms personally in the hypobaric (altitude) chamber during a high altitude-training course is that you will know what to look for while you are flying. This is important because your signs and symptoms of hypoxia will remain relatively constant throughout your flying career.
TIME OF USEFUL CONSCIOUSNESS (TUC) OR EFFECTIVE PERFORMANCE TIME (EPT)
These interchangeable terms describe the period of time between the interruption of the oxygen supply or exposure to an oxygen-poor environment and the time when a pilot is unable to perform flying duties effectively, such as putting on oxygen equipment or descending to a safe altitude. Table 2 shows the average TUC or EPT for various altitudes. The table is to be used as a guide only; the times are based on healthy individuals at rest in a hypobaric (altitude) chamber. One important fact to keep in mind is that following a rapid decompression to and above 30,000 feet, the average TUC/EPT will be reduced from 1/3 to 1/2 its original value. This is due to phenomenon known as reverse diffusion or fulminating hypoxia. This occurs when oxygen is forced out from the lungs due to the rapid expansion of gas during a rapid decompression. The result is acute and immediate hypoxia.
FACTORS INFLUENCING TOLERANCE TO HYPOXIA
It is impossible to predict exactly when, where, or how hypoxic reactions will occur in an individual pilot. The appearance and severity of the signs and symptoms are aggravated by several factors; rate of ascent, time spent at altitude, physical activity at altitude, fatigue, self-imposed stress, extreme ambient temperature, and individual physiological fitness.
PREVENTION OF HYPOXIA
There is nothing magic about preventing hypoxia; fly a well-maintained pressurized airplane or fly at an altitude where oxygen is not required. Obviously this is not always practical, and by following these simple guidelines you will be able to reduce your chances of experiencing hypoxia during flight. If pressurization is not an option and supplemental oxygen is not available, limit your exposure time to less than 1 hour between 10K feet and 14K feet, including not more than 30 minutes between 12K feet and 14K feet. If you have supplemental oxygen, use it above 5K feet during night flights and above 10K feet during daytime flights.
TREATMENT OF HYPOXIA
If hypoxia is suspected in yourself or others on board an aircraft, follow these simple steps:
*Check your equipment for proper operation
*Administer supplemental oxygen (don your oxygen mask)
*Ensure the regulator is turned on
*Check the flow indicator (this will tell you that something is coming to the mask)
*Monitor your breathing rate and depth (intentionally slow your breathing to prevent hyperventilation, use the flow indicator to help you monitor respiration)
*If safe, descend to an altitude (below 10K feet) where supplemental oxygen is no longer required
SOME FINAL THOUGHTS
Hypoxia is a constant and dangerous companion while flying. The insidious nature of hypoxia means that you must constantly be suspicious of how you and your passengers feel. Once hypoxia is recognized, quick and decisive action means recovery is only seconds away. The key, then, to flying safely at altitude is to be able to: identify the flight condition in which you may become hypoxic, recognize your personal hypoxia symptoms, and to recover from hypoxia before you have gone beyond your ability or desire to help yourself.
http://www.cami.jccbi.gov/aam-400/beware.htm