Define the concept of time of useful consciousness.

This describes the amount of time that once a person becomes hypoxic they can remain conscious enough to recognise what is happening and do something about it

Describe how hypoxia can be treated.

To treat hypoxia; 

Administer Oxygen from an oxygen supply source
Descend the aircraft to 10,000 ft AMSL or below

State the factors that affect the likelihood of suffering from hypoxia.

• Carbon Monoxide
• Cough / cold or chest infection
• Hangover
• Alcohol and drug
• Excessive movement about the aircraft
• Subjection to cold temperatures
• Subjected to G force
• Anemia
• Fatigue
• Smoker 

Describe how hypoxia can be prevented.

• Avoid flying when unwell / chesty
• Avoid G loading
• Avoid hangovers, alcohol, drug use
• Check for anemia
• Avoid fatigue
• Reduce smoking
• Watch for early warning signs
• Avoid excessive movement about the cabin

Explain the relationship between hypoxic onset and both vision and cognitive performance. 

The most complex parts of the brain use the most amount of oxygen, and so will be affected earlier by hypoxia;

resulting in vision loss and reduced cognitive performance 

Explain the reasons hypoxia symptoms are difficult to detect.

The onset can be very subtle and gradual so is not noticed straight away

Describe the common symptoms of hypoxia.

• Fuzzy thick feeling of the head
• Slowness of thought
• Poor or lack of judgement
• Clumsiness
• Euphoria
• Mental fixation on trivial tasks
• Loss of visual sharpness, dimming, tunnel vision reduced colour vision
• Deep sighs and hyperventilation
• Blue peripheries (fingers, lips) 

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Explain the causes of hypoxia.

Hypoxia is caused when the oxygen breathed into the lungs has not got sufficient pressure to be able to diffuse through the lung semipermeable membrane into the bloodstream

Thus the body cells have an inadequate delivery of oxygen

Explain the mechanical effect of the partial pressure of oxygen on oxygen transfer in the lungs. 

When the partial pressure of the oxygen in the lungs is or over 102 mmHg then this allows for transfer of oxygen through the lungs to bloodstream

State the partial pressure of oxygen both inside and outside the lungs at sea level.

At sea level the atmospheric air pressure is 760mmHg.

Oxygen makes up 21% of this air which would equate to about 160mmHg of partial pressure

Inside the lungs the minimum pressure that the oxygen must be for diffusion into the bloodstream is 102mmHg

The partial pressure of O2 decreases once breathed in due to the presence of carbon dioxide and water vapour inside the lungs