Physiological response to high barometric pressure

Hyperbarism:• When human beings descend beneath the sea,

the pressure around them increases tremendously and exposes the blood in the lungs to extremely high alveolar gas pressure.

Relationship of pressure to sea depth

Boyle’s law:

Volume 1/α Pressure

Effect of High Partial Pressures of IndividualGases on the Body• Nitrogen Narcosis• Oxygen Toxicity

Nitrogen Narcosis• At 120 feet feels joviality & careless• At 150 to 200 feet, the diver becomes drowsy. • At 200 to 250 feet, loss of strength.• Beyond 250 feet, becomes unconsciousnessNitrogen narcosis similar like alcohol intoxication

Nitrogen reacts with fatty acids in cell memb of neurons and impairs the conduction like gas anesthetics

Oxygen Toxicity

Acute oxygen poisoning:•Nausea•muscle twitchings•dizziness•disturbances of vision•Irritability•Disorientation•seizures followed by coma

Generation of oxygen free radicals swamp the enzyme system to remove it

Reacts with polyunsaturated fattyacids of cell memb causes brain dysfunction

Chronic Oxygen Poisoning: Causes Pulmonary edema

Decompression of the diver after excess exposure to high pressure

Decompression Sickness (Synonyms: Bends, Compressed AirSickness, Caisson Disease, Diver’s Paralysis, Dysbarism)

Symptoms:• Pain in the joints• Pain in the muscles of arms & neck• Nervous system symptoms: dizziness, paralysis &

unconsciousness• Shortness of breathing (chokes)• Death

Physiological principles of prevention and management of decompression sickness

Decompression table:60 minutes at a depth of 190 feet• 10 minutes at 50 feet depth• 17 minutes at 40 feet depth• 19 minutes at 30 feet depth• 50 minutes at 20 feet depth• 84 minutes at 10 feet depth

Decompression chamber

Scuba (Self-Contained Underwater Breathing Apparatus) Diving

Contains oxygen & helium

Helium• Has only about one fifth the narcotic effect of

nitrogen

• Only about one half as much volume of helium dissolves in the body tissues as nitrogen

• Low density of helium (one seventh the density of nitrogen) keeps the airway resistance for breathing at a minimum work of breathing

The deepest SCUBA dive record-Ahmed garb, 1090 ft in Red sea

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