PHYSIOLOGY OF DEEP SEA DIVING
- Pressure rises at depth, just as pressure falls at high altitude.
- Pressure rises very fast on a descent to relative small depth.
– Since, specific gravity of water is much higher than air.
- Pressure exerted by every 10 meters (33-foot) descent in water is one atmospheric (760 mm Hg).
- Hence, a person at only 10m underwater is exposed to doubled atmospheric pressure –
- In compressed air, say at 4 atm (3000 mm Hg) –
– All gases have partial pressures 4 times the normal.
- Hence,
– PO2 in compressed air appox. 600 mm Hg.
– PN2 approx. 2400 mm Hg.
– Pressure in alveoli & arteries are also very high.
- Gases spread throughout body fluids, remain dissolved at high pressure.
– Causes undesirable symptoms.
- Work of breathing increases
– Due to high density of compressed gases.
– Requiring much increased respiratory effort
- On breathing compressed air,
– Increased PO2, causes “Oxygen Toxicity”.
– Increased PN2, causes “Nitrogen Narcosis”.
- Is the resultant effect of gaseous nitrogen on diver’s brain below sea depth of 100 feet.
– Approx. 30 – 40m below sea level.
– At pressures of 4-5 atmosphere
- Usually, nitrogen inert gas which at sea-level pressure has no significant body effect.
- At higher atmospheric pressure,
– Nitrogen dissolves in body fluid.
– Much easily dissolves in fatty substances of neuronal membrane.
– Thus, producing necrosis.
- Referred as “Raptures of the deep” –
– Since symptoms resemble “Alcohol Intoxication”.
SYMPTOMS:
- Earliest – Euphoria.
- Later develops,
– Drowsiness.
– Lightheadedness.
– Fixation of ideas.
– Loss of balance.
– Incoordination of movements.
-Difficulty in concentration.
- Ultimately, unconsciousness & death may occur.
CAISSON’S DISEASE / DECOMPRESSION SICKNESS / DIVER’S PARALYSIS / DYSBARISM / BENDS:
- Form of gas embolism.
- Occurs with individuals exposed to sudden lowering of atmospheric pressure.
- Rapid ascent of scuba & deep sea divers.
- Individuals in unpressurized aircraft in rapid ascent (e.g., in Pilots).
- Underwater construction workers.
- Extra-vehicular activity from spacecraft.
EFFECTS:
Air breathed at high pressure (e.g., during a deep-sea dive).
Increased amounts of gas (particular nitrogen) dissolve in blood & tissues.
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On ascending diver depressurizes too rapidly → Resulting in expansion of nitrogen in tissues.
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Bubbles out in blood to form gas emboli.
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Forms & migrate to any body part producing symptoms.
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Effects vary from joint pain, tissue ischemia to paralysis & death.
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Rapid formation of gas bubbles within skeletal muscles & supporting tissues around joints is responsible for painful condition called “Bends”.
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ln lungs – Edema hemorrhages, & focal atelectasis/emphysema may appear, leading to respiratory distress
- Referred as “Chokes”.
TREATMENT OF GAS EMBOLISM:
- Individuals are placed in compression chamber.
– Where barometric pressure raised → Forcing gas bubbles back into solution.
- Subsequent slow decompression theoretically permits gradual resorption & gas exhalation.
- Hence, obstructive bubbles do not reform.
Exam Important
- Because at higher atmospheric pressure, nitrogen dissolved in body fluid & even more easily dissolves in fatty substances in neuronal membrane & produces necrosis.
- A particular form of gas embolism.
- Occurs with individuals exposed to sudden lowering of atmospheric pressure.
- Rapid ascent of scuba & deep sea divers.
- Individuals in unpressurized aircraft in rapid ascent (e.g., in Pilots).
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