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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