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A pilot who is a moderate smoker, regularly complains that he/she can’t see ground features as well as other members on night flights above 5 000 ft. Which of the following can explain why the pilot takes longer than other crew members to adapt to night vision?

1. Inhaling carbon dioxide from smoking or exhaust fumes 
2. Inhaling carbon monoxide from smoking or exhaust fumes 
3. The onset of hypoxia as the aircraft climbs above 5000 ft 
4. The onset of anoxia as the aircraft climbs above 5000 ft

  • A
    1 and 3.
  • B
    1 and 4.
  • C
    2 and 3.
  • D
    2 and 4.

SMOKING AND HYPOXIA

Smoking produces carbon monoxide which is inhaled. Inhaled carbon monoxide passes easily into the bloodstream where it enters the red blood cells and binds to the haemoglobin. Carbon monoxide binds to haemoglobin much more strongly than oxygen, resulting in a stable compound, carboxyhaemoglobin. Consequently, it prevents the carriage of oxygen from the lungs to the tissues, so that the tissues become hypoxic and thus increasing the smoker’s physiological altitude and making him/her more susceptible to hypoxia.

  • Vision is the first of the senses to be affected by a lack of oxygen. This is especially true of night vision. Even at a relatively low altitude of approximately 5000 feet, where no other effect of hypoxia can be detected, night vision is appreciable reduced.

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