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Physiology

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9 out of 33
 

Earliest change in high alitiude is(Latest Questions)



A Hyperventillation
B Decrease in work capacity

C Drowsiness
D Polycythemia

Ans. A Hyperventillation

Effect of decreased Barometric pressure due to increasing (high)altitude Lead to PO2

I. At 3000m (10,000 feet) — Po is 6OmmHg (above the sea level)Hypoxic stimulation of chemo receptors es ventilation (Hyper ventilation Q) fall in arterial PCO2Respiratory alkalosis Q

II. Acute Hypoxic symptoms -Acute mountain sickness in unacclimatized persons: -

a. At 3700m (12000 feet) symptoms :irritability, drowsiness, lassitude, mental and muscle fatigue.

b. Above 18,000 feet seizures

c. Above 23,000 feet (conciousness lost)

III. Delayed effects of high altitude -

This syndrome develops 8-24 hours after arrival and last 4-8 days. It is C/B: -

a. Headache, irritability, insomnia, breathlessness and nausea and vomitting. Q

b. Cause cerebral edema due to arteriolar dilation Q

c. T/t for Alkalosis Acetazolamide and for cerebral edema gluco-corticoids Q

d. High altitude pulmonary edema is a serious form of mountain sickness pulmonary edema prone to occurs inindividual who ascend quickly to altitudes above 2500m and engage in heavy physical acitvity during the first 3 days after arival. It is associated with marked pulmonary hypertension. Nifedipine is of value in the t/t and prevention of the condition, also rest and O2. Q

IV. Acclimatization refers to changes in the body tissues in response to long term exposure to hypoxia i. e. at high altitude for days, weeks or years the person becomes more and more acclimatized to low PO2. The principal means by which acclimatization comes about are: -

a. A great increase in pulmonary ventilation Qon immediate exposure to very low Po2, the hypoxic stimulation of the chemoreceptors increase alveolar ventilation about 65% above normal. This is immediate compensation for the high altitude. ”

b. Increased in RBC Q Due to hypoxia →↑erythropoietin polycythemia

c. Increased diffusion capacity of lungs Qit increased three folds above the normal; and Increased T. L. capacity.

d. Pulmonary Hypertension Q Note that hypoxia causes vasoconstriction in lungs.

e. Increased vascularity of the tissue Qdensity es in skeletal and cardiac muscle.

f. Increased ability of the cells to use O2, despite the low PO2Qdue to ed conc of oxidative enzymes and ed density of mitochondria at cellular level.

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