Soal Latihan dan Jawaban Reading Comprehension 89
Under certain circumstance the human body must cope with gases at greater-than
normal atmospheric pressure. For example, gas pressures increase rapidly during a dive
made with scuba gear because the breathing equipment allows divers to stay
underwater longer and dive deeper. The pressure exerted on the human body increases
(5) by 1 atmosphere for every 10 meters of depth in seawater, so that at 30 meters in
seawater a diver is exposed to a pressure of about 4 atmospheres. The pressure of the
gases being breathed must equal the external pressure applied to the body; otherwise
breathing is very difficult. Therefore all of the gases in the air breathed by a scuba
diver at 40 meters are present at five times their usual pressure. Nitrogen which
(10) composes 80 percent of the air we breathe usually causes a balmy feeling of
well-being at this pressure. At a depth of 5 atmospheres nitrogen causes symptoms
resembling alcohol intoxication known as nitrogen narcosis. Nitrogen narcosis
apparently results from a direct effect on the brain of the large amounts of nitrogen
dissolved in the blood. Deep dives are less dangerous if helium is substituted for
(15) nitrogen, because under these pressures helium does not exert a similar narcotic effect.
As a scuba diver descends, the pressure of nitrogen in the lungs increases. Nitrogen
then diffuses from the lungs to the blood and from the blood to body tissues. The
reverse occurs when the diver surfaces; the nitrogen pressure in the lungs falls and the
nitrogen diffuses from the tissues into the blood and from the blood into the lungs. If
(20) the return to the surface is too rapid, nitrogen in the tissues and blood cannot diffuse
out rapidly enough and nitrogen bubbles are formed . They can cause severe pains,
particularly around the joints.
Another complication may result if the breath is held during ascent. During ascent
from a depth of 10 meters, the volume of air in the lungs will double because the air
(25) pressure at the surface is only half of what it was at 10 meters. This change in volume
may cause the lungs to distend and even rupture. This condition is called air embolism.
To avoid this event, a diver must ascent slowly, never at a rate exceeding the rise of
the exhaled air bubbles, and must exhale during ascent.
Reading Comprehension 89
The effects of pressure on gases in the human body
The equipment divers use
How to prepare for a deep dive
The symptoms of nitrogen bubbles in the bloodstream.
It goes directly to the brain
It has a narcotic effect
It forms bubbles
It is reabsorbed by the lungs
An air embolism