Hypoxia / Hyperventilation

HYPOXIA

Definition: a deficiency in the amount of oxygen reaching bodily tissues

Symptoms: 

• apprehension
• air hunger
• cyanosis (blue discolouring of fingernails)
• headache
• euphoria
• loss of colour vision (the retina of the eye is very sensitive to hypoxia)
• tingling extremities

Time of Useful Consciousness:

• 25 000 ft: 3 to 6 minutes
• 30 000 ft: 45 to 75 seconds
• 40 000 ft: 13 to 30 seconds

Treatment: descend to lower altitude and/or breathe 100% oxygen

HYPERVENTILATION

Definition: an abnormal increase in the rate and depth of breathing, resulting from abnormally low level of carbon dioxide in the blood

Could be triggered by emotional tension / anxiety

Symptoms:

• dizziness
• tingling extremities
• hot / cold sensations
• nausea
• sleepiness

Treatment: consciously slow breathing rate.  Try breathing into a paper bag (i.e. re-breathe expelled CO2)

HYPOXIA / HYPERVENTILATION

There are very few distinguishable differences between the signs and symptoms of hypoxia and hyperventilation.  If unable to ascertain which one a passenger is suffering from, treat for hypoxia first. 

More info in Transport Canada's Handbook for Civil Aviation Medical Examiners.