- High altitudes lead to hypoxia due to decreased barometric pressure reducing oxygen levels. Symptoms appear above 10,000 feet and become severe above 15,000-18,000 feet. The body compensates through hyperventilation and other physiological changes over time. - Deep sea diving exposes divers to high pressure, leading to hazards like nitrogen narcosis, oxygen toxicity, and decompression sickness if ascending too quickly. Special breathing gases and slow recompression are needed to prevent these risks during deep dives. - Both high altitudes and deep sea diving cause hypoxic stresses on the body that require physiological adaptations and safety precautions to tolerate the environmental challenges.

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