8. One of the major hazard for deep-sea divers is the “bend”. 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 brathes air at higher perssures. This result 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 release 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 capilaries. 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 under water. There are other factors that a diver must take into account when determining a safe ascent rate. These include the diver’s sex and body build, the number of divers undertaken within the previous 12 hours, the time spent at the dive location befor 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
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. Which of the following does not affect the desaturation of body tissues?
A. The location of the diver
B. The number of the previous divers.
C. The composition of the gas being use.
D. The amount of activity under water
4. According to the passage, bends
A. is the major diving hazard
B. reduced pressure in the bloodstream
C. is a condition caused by diving too quickly
D. is a direct result of dying body tissues
5. According to the passage, which of the following is not true?
A. Air at higher pressure is taken in at greater depths
B. More air is dissolved into the bloodstream at increasing depths
C. Carbon dioxide stays in the body when the diver ascends.
D. Body tissues are saturated at different rates
