Physiology Of Deep Sea Diving

PHYSIOLOGY OF DEEP SEA DIVING

Q. 1

Caisson’s disease is:

 A

Gas embolism

 B

Fat embolism

 C

amniotic fluid embolism

 D

tumor embolism

Q. 1

Caisson’s disease is:

 A

Gas embolism

 B

Fat embolism

 C

amniotic fluid embolism

 D

tumor embolism

Ans. A

Explanation:

Gas embolism [Ref: Guyton 11/e p548; Robbin’s 8/e p127]

  • Caisson’s disease, (also called Decompression sickness, Bends, Diver’s Paralysis, Dysbarism) is a particular form of gas embolism, which occurs when individuals are exposed to sudden lowering of atmospheric pressure like –rapid ascend of scuba and deep sea divers, individuals in unpressurized aircraft in rapid ascent, undenvater construction workers and extra-vehicular activity from spacecraft.
  • When air is breathed at high pressure (e.g., during a deep sea dive), increased amounts of gas (particularly nitrogen) become dissolved in the blood and tissues. If the diver then ascends (depressurizes) too rapidly, the nitrogen expands in the tissues and bubbles out of solution in the blood to form gas emboli.
  • Since bubbles can form in or migrate to any part of the body, it can produce many symptoms, and its effects may vary from joint pain, ischemia in tissues to paralysis and death.
  • The rapid formation of gas bubbles within skeletal muscles and supporting tissues in and about joints is responsible for the painful condition called the bends. In the lungs, edema, hemorrhages, and focal atelectasis or emphysema may appear, leading to respiratory distress, the so-called chokes.
  • Treatment of gas embolism requires placing the individual in a compression chamber where the barometric pressure may be raised, thus forcing the gas bubbles back into solution. Subsequent slow decompression theoretically permits gradual resorption and exhalation of the gases so that obstructive bubbles do not re-form.

Q. 2

Decompression sickness is seen in:

 A

Diver

 B

Pilot

 C

Diver and pilot

 D

A & C

Q. 2

Decompression sickness is seen in:

 A

Diver

 B

Pilot

 C

Diver and pilot

 D

A & C

Ans. D

Explanation:

A i.e. Diver; B i.e. Pilot; C i.e. Divers and pilot

– Caisson’s Disease is nitrogen (N2) gas embolismQ seen in deep sea divers and aviators (pilots)Q on sudden decompression.

–                          Air embolim occurs in neuro-cranial surgery and escape from submarines (i.e. person breathing compressed air from a tank). Because the veins in the skull are in non-collapsible chamber, so they cannot collapse and a negative (suction) pressure develops in dural sinuses (- 10 mmHg in saggital sinus in standing position). Therefore if dural sinus is opened during surgery, air can be sucked (causing air embolism) in venous system. Similarly when a person ascends (from deep sea in submarine) the gases in lung expand and sometimes rupture pulmonary blood vessel, forcing the gases (air) to enter the vessels and cause air embolism.

Decompression sickness
(Compressed Air Sickness, Dysbarism, Air Sickness, Bends, Diver’s Paralysis, Caisson’s Disease)

The disorder occur when a person returns rapidly to normal surroundings (atmospheric pressure) after exposure to high atmospheric pressure, as in deep sea.

Because of Ted barometric pressure at deep sea, compression occurs. This compression reduces the volume of gases in the body.

–  Due to sudden return to atmospheric pressure, the NT2 is decompressed and escapes from the tissue. Being a gas it forms bubbles, the bubbles obstruct the blood flow producing air embolism.

–  AviatorsQ may develop decompression sickness if they are suddenly decompressed at very high altitudes as a result of cabin failure.

It manifest as bends (joint pain most commonly in knee), staggers (vertigo d/t formation of bubbles in vestibular apparatus), chocking sensation, paresthesias accompanied by rashes & itching.

Mountaineer suffer from mountain sickness due to decreased barometric pressure.


Q. 3

Nitrogen narcosis is caused due to:

 A

Nitrogen inhibits dismutase enzyme

 B

Increase production of nitrous oxide

 C

Increased solubility of nitrogen in nerve cell membrane

 D

Decrease in oxygen free radicals

Q. 3

Nitrogen narcosis is caused due to:

 A

Nitrogen inhibits dismutase enzyme

 B

Increase production of nitrous oxide

 C

Increased solubility of nitrogen in nerve cell membrane

 D

Decrease in oxygen free radicals

Ans. C

Explanation:

C i.e. Increased solubility of nitrogen in nerve cell membrane

Nitrogen narcosis (toxicity) or raptures of death sets in at around 120 feet and below sea surface because at high tissue concentrations, N2 behave as anesthetic gases and show increased solubility in lipid (fatty) substances of neuronal membrane and makes them less excitable by altering ionic conductanceQ.

N2 Narcosis

– At high tissue concentrations, N2 and other rare gases such as helium & argon behave as anesthetic gases – Mild N2 narcosis sets in at round 120 feet below sea surface and individual feels like one intoxicated with alcohol & is in high spirits exhibit a joviality & loses his cares a phenomenon referred as raptures of death. Manual dexterity is maintained but intellectual function is impaired.

– At 150-200 feet, diver becomes drowsy; at 200-250 feet strength decreases & becomes too clumsy to perform required work. Beyond 250 feet (8.5 Atm. Pressure)becomes almost useless.

At high concentrations, nitrogen behaves as anesthetic gases and show increased solubility in lipid (fatty) substances of neuronal membrane and makes them less excitable by altering ionic conductanceQ.

Oxygen toxicity

– Breathing high concentration (or very high alveolar 02 pressure) causes lung damage, nausea, muscle twitching, dizziness, irritability, disorientation, disturbances of vision and brain seizure followed by coma.

Above a critical alveolar P02 (> 2 atmP), the hemoglobin – 02 buffering mechanism fails & tissue P02 rises to hundreds or thousands of millimeters of mercury

At these high levels amount of toxic oxidizing free radicals (such as superoxide free radical 02 & peroxide free radical in form of hydrogen peroxide) swamp the enzyme systems (peroxidases, catalses, and superoxide dismutases) designed to remove them

In excess, free radicals oxidize the poly unsaturated, fatty acids of cell membrane and some cell enzymes. The nervous tissues with its high lipid content is particularly vulnerable. There fore acute lethal 02 toxicity is caused by brain dysfunction.



Q. 4

True combination is all except –

 A

Cold-Trench foot

 B

Light-Miner’s nystagmus

 C

Pressure-Caisson disease

 D

Cane fibre-Farmer’s lung

Q. 4

True combination is all except –

 A

Cold-Trench foot

 B

Light-Miner’s nystagmus

 C

Pressure-Caisson disease

 D

Cane fibre-Farmer’s lung

Ans. D

Explanation:

Ans. is ‘d’ i.e., Cane fibre Farmer’s lung 

Farmer’s lung is caused by Hay (grain dust).



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