Deep-sea diving hazards. One of the major hazards for deep-sea divers is the bends. This condition is caused by gas bubbles forming in the bloodstream if the diver ascends

One of the major hazards for deep-sea divers is the "bends." This condition is caused by gas bubbles forming in the bloodstream if the diver ascends too rapidly. The reason for this condition has to do with the saturation and desaturation of body tissues with various gases. At increasingly greater depths, the diver breathes air at higher pressures. This results in an increased quantity of air being dissolved in the bloodstream. Different body tissues are saturated with different gases from the air at different rates. When the diver ascends, oxygen is used by the body tissues, carbon dioxide is released quickly, and nitrogen remains. The nitrogen needs to be released gradually from the bloodstream and body tissues. If nitrogen is subjected to a too rapid pressure reduction, it forms gas bubbles in the blood vessels. The bubbles become trapped in the capillaries. This prevents blood and oxygen from supplying necessary nutrients to body tissues, which consequently begin to die.

Saturation and desaturation are affected by various factors such as the depth, length of time, and amount of exertion underwater. There are other factors that a diver must take into account when determining a safe ascent rale. These include the diver's sex and body build, the number of dives undertaken within the previous 12 hours, the time spent at the dive location before the dive, and the composition of the respiration gas.

1. The passage is mainly about

(A) how to calculate a safe depth when diving

(B) how to determine saturation and desaturation rates

(C) instructions for diving safely

(D) the factors causing the bends in divers

2. According to the passage, gas bubbles

(A) trap the capillaries

(B) are gradually released from the tissues and bloodstream

(C) block the supply of nutrients to body tissues

(D) are formed from compressed air

3. According to the passage, the bends

(A) is the major diving hazard

(B) reduces pressure in the bloodstream

(C) is a condition caused by diving too quickly

(D) is a direct result of dying body tissues

4. Which of the following does NOT affect the desaturation of body tissues?

(A) The location of the dive

(B) The number of previous dives

(C) The composition of the gas being used

(D) The amount of activity underwater

5. Письменно переведите на русский язык весь текст.

Date: 2015-12-12; view: 2539; Нарушение авторских прав