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physiology of deep sea driving and baro,metric pressures
- 1. PHYSIOLOGY OF DEEPSEA DR RASHMI
- 2. INTRODUCTION • Atmospheric pressureof 760 mm Hg at sea level is considered 1 atmospheric pressure. • Pressure increases by 1 atm for a depth of every 10 m (33 ft) as one descends beneath the sea. Thus, a person under sea at a depth of 10 m (33 ft) is exposed to a pressure of 2 atm, 1 atm due to the air above the sea level and another 1 atm due to 10 m column of water. As the depth under sea increases the pressure also increases proportionately
- 3. • Decrease involume of gases occurs due to compression as the pressure increases under sea. • According to the Boyle’s law the volume to which a given quantity of gas is compressed is inversely proportional to the pressure. • With increase in the pressure the volume is decreased proportionately
- 4. • High atmosphericpressure is met under following conditions - Deep sea diving, - Going under the sea in submarines and - Caisson’s workers, i.e. the men who dig underwater tunnel, work in a chamber (Caisson’s chamber) in which atmospheric pressure is high to prevent entry of water.
- 5. • Physiological problemsassociated with life under high pressure may be divided into: Physiological problems at depth (due to compression effect of high atmospheric pressure) and Physiological problems of ascent (due to decompression phenomenon)
- 7. PHYSIOLOGICAL PROBLEMS UNDERDEPTH • At a depth of more than 30 m (100 ft) due to mechanical effects of increased atmospheric pressure there may occur: -Caving in of the chest, - Damage to the face - Squeezing of air in the paranasal sinuses and middle ear.
- 8. EFFECTS OF INCREASEDBAROMETRIC PRESSURE( DEEP SEA DIVING) • For every 33 ft(10 m) of descent there is increase by 1 atmosphere. High pressure in deep sea causes some hazards. • People using underwater chambers called Caisson are also exposed to high pressures. • In deep seas gas mixtures are inhaled at high pressures to cause proper expansion of the thorax. • Inhaled gases at high pressures dissolve in body fluids in large quantities and are hazardous
- 9. HAZARDS OF DEEPSEA DIVING • Nitrogen narcosis • High pressure nervous syndrome • Acute oxygen toxicity • Dysbarism • Air embolism
- 10. Effects of increasedpO2 (oxygen toxicity) 1. Oxygen toxicity may be acute or chronic. Acute oxygen toxicity occurs on exposures to 4 atm pres sure of oxygen (pO2 in lungs about 3000 mm Hg). • Acute oxygen poisoning is typically characterized by ner vous system complications as the brain tissue is especially susceptible to acute oxygen poisoning. • At high tissue pO2 the molecular oxygen is converted into active oxygen, i.e. superoxide anion (O2 −) which is free radical. • Nervous complications of acute oxygen poisoning include disorientation, dizziness, convulsions and even coma.
- 11. Effects of increasedpO2 (oxygen toxicity) Chronic oxygen toxicity occurs due to prolonged expo sure (8–24 h) to oxygen at 1 or 1.5 atmospheric pressure
- 12. NITROGEN NARCOSIS • Indeep sea diving, gases are inhaled at high pressure. Inhalation of 100% O2 causes CNS depression • Normally 20%O2 and 80%N2 are inhaled. N2 at high pressure produces narcotic effects like euphoria etc • Features are similar to alcoholic intoxication. Manual agility is unaffected, intellectual functions are altered. • Mainly due to anesthetic effect of N2
- 13. HIGH PRESSURE NERVOUSSYNDROME • In place of N2 a mixture of O2 and helium is used as narcotic effects of He are less than that of N2. • Work of breathing is less with He compared with N2 due to decreased resistance to airflow • He is less soluble in body fluids. • HPNS occurs due to anesthetic effects of he at high pressure due to its lipid solubility and direct effect on neuronal membrane. • Tremors, drowsiness and incoordination are present.
- 14. DYSBARISM • Also knownas Decompression Sickness. • When subjects exposed to high pressures are suddenly brought to low pressures rapidly. • Deep sea divers usually breathe 80% N2. N2 dissolves in body lipids at high pressures as it is lipid soluble • If return to surface is slow- gases come out of blood and are eliminated by lungs • Rapid ascent causes rapid escape of gases from fluids and bubbles are formed in blood and tissues causing damage, pain
- 17. Symptoms of decompressionsickness • Pain in joints and muscles of legs or arms. The joint pain accounts for the term ‘bends’ that is often used to describe the decompression sickness. • Sensation of numbness. • The chokes. The chokes refer to the serious shortness of breath which is often followed by severe pulmonary oedema, and occasionally death. • Paralysis of muscles may occur temporarily due to escape of nitrogen bubbles from the myelin sheath of motor nerves. This is called diver’s palsy (one of the names of this disease). • Coronary ischaemia or myocardial infarction may occur due to the blockage of coronary capillaries by the nitro gen bubbles. • Neurological symptoms like dizziness, paralysis of mus cles, or collapse and unconsciousness may occur due to the blockage of blood vessels of brain and spinal cord.
- 18. • In severecases- bubbles decrease blood flow to brain and spinal cord resulting in various sensory and motor deficits • Bubbles in pulmonary capillaries- produce dyspnoea and in coronary vessels- produce myocardial ischemia • Treatment- recompression in a pressurised cabin • Prevention- slow ascent. Reduction in pressure should not exceed 50%
- 19. AIR EMBOLISM • Airembolism is another physiological problem which may occur during the rapid ascent from a depth below the sea level. • Manifestations of air embolism include chest pain, tachy pnoea, systemic hypotension and hypoxaemia. • In severe cases, air emboli may travel to the systemic circulation, block the blood flow to some vital organs and may even result in death.
- 20. SCUBA • SCUBA (self containedunderwater breathing apparatus) is used by the deep sea divers and the underwater tunnel workers, to prevent the ill effects of increased barometric pressure in deep sea or tunnels.
- 21. • This instrumentcan be easily carried and it contains air cylinders, valve system and a mask. By using this instrument, it is possible to breathe air or gas mixture without high pressure. • Also, because of the valve system, only the amount of air necessary during inspiration enters the mask and the expired air is expelled out of the mask
- 22. • Disadvantage ofthis instrument is that the person using this can remain in the sea or tunnel only for a short period. • Especially, beyond the depth of 150 feet, the person can stay only for few minutes.
- 23. Use of breathingmixture containing helium and low oxygen concentration • Use of breathing mixture containing helium and low oxy gen concentration is less harmful than natural air because: - Low oxygen concentration prevents occurrence of oxygen toxicity. - Helium when replaced with nitrogen provides following advantages: - Because of its smaller molecule and lower density than nitrogen it is easier to breathe, it diffuses faster and it is easier to eliminate its bubbles from the body..
- 24. Use of breathingmixture containing helium and low oxygen concentration - The amount of helium trapped in the body under high atmospheric pressure is much less than that of nitrogen because its solubility in the body fluids is less than half that of nitrogen. - Being less toxic than nitrogen, its narcotic effect is only one-fifth that of nitrogen