High altitude physiology and human factors
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High Altitude Physiology and Human Factors. Audio required make sure your volume is tuned up!. October 4, 2006. Introduction. Define the atmosphere in terms of its characteristics and human adaptability.

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High altitude physiology and human factors

High Altitude Physiology and Human Factors

Audio required make sure your volume is tuned up!

October 4, 2006


  • Define the atmosphere in terms of its characteristics and human adaptability.

  • Describe how gases in our bodies will respond to changes in the environment, and how this impacts our performance.

  • Review causes and hazards of hypoxia and hyperventilation

As we ascend
As we ascend

  • The combination of pressure and oxygen percentage determine our ability to perform.

  • What altitudes do you first notice effects?

  • Our environment changes…

    • predictably,

    • gradually,

    • to the point where we are in a hostile environment,

    • and well beyond our ability to adapt and survive.

Types of hypoxia and causes
Types of Hypoxia and Causes

  • Hypoxic

  • Histotoxic

  • Hypemic

  • Stagnant

Hypoxic hypoxia
Hypoxic Hypoxia

  • A lack of oxygen partial pressure in the lungs or a reduction in the gas exchange area caused by:

    • Altitude

    • Drowning

    • Pneumonia

    • Chronic Lung Disease

  • Location of Impediment

    • Lungs

  • Hypoxic hypoxia is the most common cause of hypoxia for a pilot due to an oxygen deficiency associated with high altitude operations

Effective performance times
Effective Performance Times

Effective Performance Times should always be a consideration.

At 25,000 feet, the maximum altitude of the Cirrus, the time of useful consciousness is about 3-5 minutes.

It is extremely important to continually monitor the oxygen system at be prepared to deal immediately with any oxygen malfunction.

Histotoxic hypoxia
Histotoxic Hypoxia

  • The lack of oxygen intake into the cell (tissue poisoning) caused by:

    • Alcohol

    • Narcotics

  • Location of Impediment

    • Cells

  • Histotoxic hypoxia is dependent on factors other than altitude.

Hypemic hypoxia
Hypemic Hypoxia

  • Inability of the blood to carry oxygen caused by:

    • Carbon Monoxide Poisoning

      • Smoking

      • Fire creates toxins that can irritate and incapacitate

    • Anemia

  • Location of Impediment

    • Blood

  • Carbon monoxide and smoking create an oxygen carrying deficiency which will degrade pilot performance

Stagnant hypoxia
Stagnant Hypoxia

  • Lack of proper blood distribution caused by:

    • “G” forces

    • Shock, fainting, etc.

    • Heart Failure

    • Cold Temperature

  • Location of Impediment

    • Blood Transportation Problem

  • Steep turns at FL250 may not be a good idea

Subjective symptoms

Air Hunger



Hot & Cold Flashes






Blurred Vision

Tunnel Vision


Mental Confusion

Increase in rate and depth of breathing



Poor Judgment

Loss of muscle coordination



Subjective Symptoms

Objective Signs

Factors influencing hypoxia


Individual Tolerance

Environmental Temperature

Psychological Factors


Rate of Ascent

Physical Activity

Duration of Exposure

Physical Fitness


Rate of Decompression

Factors influencing hypoxia


  • Use oxygen in compliance with the regulations

15,000 MSL:Crew must use Oxygen, and must be provided to each occupant

14,000 MSL:Crew must use Oxygen for flights duration

12,500 MSL:Crew must use Oxygen after 30 min

Prevention and considerations
Prevention and Considerations

  • Use of pulse oximeter

    • Adjust the flow of oxygen to maintain saturation levels above 90%

  • Cannulas vs Masks

    • Cannulas can not be used above FL180 as per FAR part 23

    • Remember where the source of oxygen is from when using a cannula. Eating and talking will decrease the amount of oxygen that is available to your lungs

Prevention and considerations1
Prevention and Considerations

  • Passengers

    • Monitor passengers for signs of hypoxia and treat accordingly

    • Passengers should be briefed on the use of oxygen during preflight

  • When to use start using oxygen?

Treatment for hypoxia
Treatment for Hypoxia

  • Recognition of hypoxia

  • 100% Oxygen

  • Return Rate and Depth of Breathing to Normal

  • Check Connections

  • Check adjustment and size of mask

  • Descend Below 10,000 feet

    • Terrain permitting


    • Supply

    • Connections

    • Regulator

    • Emergency connection

    • Adjustment

    • Mask condition

High altitude physiology and human factors

An abnormal increase in the rate and depth of breathing.

Results in exhaling too much Carbon Dioxide.








Pressure Breathing



Subjective symptoms1



Visual Problems



Light Headedness

Muscle Twitching

Cold, clammy skin

Muscle Tightness



Subjective Symptoms

Objective Signs

Treatment for hyperventilation

100% Oxygen

Return Rate and Depth of Breathing to Normal

Check Connections

Paper Bag Method

Used at altitude where supplemental oxygen is not required or needed

Talk or sing to control the rate of breathing.

Treatment for Hyperventilation

Other physiological affects of altitude pressure change
Other Physiological Affects of Altitude/Pressure Change

  • Decompression sickness

    • Caused by the formation of nitrogen bubbles in the blood and tissues following a sudden drop in the surrounding pressure, as when ascending rapidly.

    • Characterized by severe pains in the joints and chest, skin irritation, cramps, and paralysis

      • Treatment

        • Decompression sickness is a medical emergency, respond appropriately.

    • NOTE: Time between scuba diving on non-decompression stop dives and flying is 12 hours. The minimum time between decompression stop diving and flying is 24 hours.

Other physiological affects of altitude pressure change1
Other Physiological Affects of Altitude/Pressure Change

  • Sinus/inner ear blockage

    • Caused by the difference in pressure from the middle ear and the outside world, most likely due to a cold, ear infection or a sore throat.

    • Treatment

      • On descent, level off and Valsalva

      • Reverse direction of pressure change

      • Retry Valsalva

      • Use reduced rates of descent and land

The eustachian tube allows air pressure to equalize in the middle ear.


  • Remember the atmosphere that we live in is much different up at altitude than it is down on the surface.

  • As a pilot you must be prepared for any physiological situation that may arise.

  • You must be able to recognize the symptoms of Hypoxia and Hyperventilation as well as be able to take the appropriate action in order to prevent conditions from getting worse.

Physiological training

UNDAF Altitude Chamber

FAA Physiological Training

Highly recommended

Experience conditions that can lead to hypoxia

Learn to recognize hypoxia

Learn about other physiological limitations when flying

Physiological Training