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Smoking cigarettes reduces the capability of the blood to carry oxygen because..
  • A
    carbon monoxide increases the partial pressure of oxygen in the alveoli.
  • B
    carbon monoxide in the smoke of cigarettes assists diffusion of oxygen in the alveoli.
  • C
    haemoglobin has a greater affinity for carbon monoxide than it has for oxygen.
  • D
    the smoke of one cigarette can cause an obstruction in the respiratory tract.

CARBON MONOXIDE

Smoking produces carbon monoxide which is inhaled. Carbon monoxide is an odourless, colourless gas. Inhaled carbon monoxide passes easily into the bloodstream where it enters the red blood cells and binds to the haemoglobin, thus preventing the carriage of oxygen from the lungs to the tissues, so that the tissues become hypoxic. Unfortunately, carbon monoxide binds to haemoglobin much more strongly than oxygen and, the resulting compound, carboxyhaemoglobin, is more stable than the equivalent compound with oxygen. In numerical terms, carbon monoxide’s affinity for haemoglobin is over 200 times as great as that of oxygen. This means that even a very low concentration of carbon monoxide in the inspired air will result in a progressive build-up of carboxyhaemoglobin to harmful levels.
  • The first symptom of carbon monoxide poisoning is a headache (or tightness across the forehead) nausea and dizziness. It is an important fact that the effects of carbon monoxide are cumulative and even a very low concentration of carbon monoxide in the inspired air will result in a progressive build-up of carboxyhaemoglobin to harmful levels. A breath of fresh air will not bring early relief and several days may be required to completely rid the body of carbon monoxide.

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