high altitude and deep sea diving.pptx

high altitudes and deep sea diving

1. High altitudes and deep sea diving Shama Praveen Tutor Department of physiology

2. Physiology of High altitudes Paul Bert studied on harmful effects due to decreased in oxygen tension in inspired air. There is no alteration of oxygen percentage at high altitudes rather the barometric pressure. Hypoxia symptoms appear at 10000 feet above and become severe at 15000- 18000 feet above. Hyperventilation as compensatory mechanism is activated. It is induced by 2 stages: first stage and second stage

3. First stage of hyperventilation It is due to hypoxic stimulation of carotid bodies. The magnitude of increase in ventilation is less because hypoxic stimulation of chemoreceptors is opposed by decrease in arterial pCO2 that occurs due to excess removal of CO2 induced by hyperventilation. This also increases arterial pH.

4. Second stage of hyperventilation Sustained increase in ventilation is due to ventilatory acclimatization (physiological response). Occurs during prolonged exposure to hypoxia. After about 2 weeks, hyperventilation induced by hypoxia reaches a stable plateau.

5. Ventilatory acclimatization has 2 mechanisms First is chemoreceptor mechanism : the pH is more alkaline so, ventilation stimulated by hypoxia brings pH to normal by movement of HCO3 out of CSF. In prolonged exposure to hypoxia, sensitivity of carotid bodies to arterial po2 also alters. Second is renal mechanism: kidney compensates pH by excreting more bicarbonate.

6. Acclimatization When a person ascends to high altitudes and stay there for long time. He slowly get adapted to new environment within 12 hours. 18000 feet above is maximum height for acclimatization.

7. Various system changes at high altitudes Respiratory changes : hypoxia stimulates peripheral chemoreceptors. It further stimulates pulmonary ventilation that leads to increase respiratory rate and depth of respiration. Ventilation increases due to active transport of H+ into CSF. Though ventilatory response decreases slowly after 4 days. Ventilatory equivalent increases with increase in height of altitude.

8. hematological changes : hypoxia stimulates production of erythropoietin which increases the formation of RBCs. it facilitates oxygen delivery to tissues. Cardiovascular changes : HR, CO& BP increases due to sympathoadrenal axis by hypoxia. Hypoxia causes vasodilation leads to increase blood flow and supply of oxygen to tissues. Tissue changes : increase in number of capillaries and mitochondria in cell. Increase in myoglobin content.

9. High altitude illness Acute mountain sickness: Chronic mountain sickness: Pulmonary hypertension: Cerebral edema:

10. Treatment Should be brought to low altitude at earliest. Diuretics: acetazolamine , furosemide Steroids: glucocorticoids (decreases cerebral edema) Oxygen therapy: hyperbaric oxygen is useful. Nifedipine: calcium channel blockers to reduce pulmonary arterial pressure.

11. Deep sea diving At sea level, the atmospheric pressure is 760mmhg and pressurein lung is equal to this pressure. For every descent of 10 meter, there is increase in pressure by 1 atmosphere. The inhaled gas at high pressure cause hazards: nitrogen narcosis, high pressure nervous syndrome, acute oxygen toxicity, dysbarium and air embolism.

12. hazards Nitrogen narcosis 20% of oxygen and 80% of nitrogen is inhaled at high pressure and produces narcotic effect. Narcotic effect starts about 120feet and become severe at or below 250 feet. High pressure nervous syndrome Mixture of helium and oxygen. It is inert at atmospheric pressure but anesthetic at high pressure coz of its lipid solubility It leads to tremors, drowsiness and incoordination.

13. Acute oxygen toxicity 100% oxygen concentration at high altitudes is toxic on CNS. Features are: nausea, dizziness, irritability, disorientation, disturbed vision. Concentration of oxygen reduced to 20% to prevent its toxicity. Dysbarium (caisson’s disease) Decompression sickness. Occur when subject exposed to high pressure are suddenly brought to low atmospheric pressure. 80% nitrogen of air moisture breathe by diver and descends into sea, nitrogen dissolves in body fluid. If return rapidly, the escape of gas from solution is quick and bubbles are formed in tissues and blood. They may lead to damage to tissues.

14. Prevention: slow recompression Treatment : recompressed immediately in a pressurized cabin Hyperbaric oxygen therapy.

15. Air embolism: subject breathes from tank and hold breathe to ascend at surface then lungs expands rapidly and ruptures pulmonary veins SCUBA: self contained underwater breathing apparatus (tank and value system) consists of cylinder containing mixture of compressed helium and oxygen gas. they are less toxic during deep sea diving.

16. Thank you