Physiological Changes At High Altitude

Question 1

Stages of compensation of hypoxia induced hyperventilation

Answer 1

1st stage: hypoxic stimul of carotid bodies. But stimul of peripheral opposed by fall in PCO2, increase in arterial pH. Alkalosis

2nd stage: 8-10 hr ventilation slowly increase, sustained. Ventilatory acclimatization. Chemoreceptor, renal mechanism. Removal of HCO3

Question 2

Respiratory changes

Answer 2

Peripheral- ventilation- rate, depth- alkalosis- kidney corrects- HCO3 excretes- urine alkaline- active transport of H+ to CSF so ventilation increases.
Ventilatory equivalent=ratio of expired minute volume to O2 consumption (VO2)

Question 3

Hematological changes

Answer 3

Increased red cell production- erythropoietin- 3 days till in high altitude- O2 supply favoured by increased in 2,3-DPG, right shift, dissociation of O2 from Hb to tissues.

Question 4

Cardiovascular changes

Answer 4

Heart rate, cardiac output, blood pressure- sympathoadrenal axis- heart rate back to normal- vasodilation- increase blood flow- O2 supply- significant polycythemia- increases viscosity- increase workload- cardiac hypertrophy

Question 5

Tissue changes

Answer 5

Capillaries
Mitochondria
Myoglobin
Oxidative enzymes- cytochrome oxidase
Angiogenesis

Question 6

Types of Illness

Answer 6

Acute mountain sickness
Chronic mountain sickness
Pulmonary hypertension and edema
Cerebral edema
Acetazolamide