<prompt> Earliest change in high altitude is:HyperventilationDecrease in work capacityDrowsinessPolycythemia  <response>: Ans. A. HyperventilationEffect of decreased Barometric pressure due to increasing highaltitude Lead to PO2 a. At 3000m 10,000 feet -- Po is 60mmHg above the sea level Hypoxic stimulation of chemo receptors es ventilation Hyper ventilation of all in arterial PCO2 --Respiratory alkalosisb. Acute Hypoxic symptoms -Acute mountain sickness in unacclimatized persons: -i. At 3700m 12000 feet symptoms: irritability, drowsiness, lassitude, mental and muscle fatigue.ii. Above 18,000 feet seizuresiii. Above 23,000 feet consciousness lostc. Delayed effects of high altitude -This syndrome develops 8-24 hours after arrival and last 4-8 days. It is CB: -i. Headache, irritability, insomnia, breathlessness and nausea and vomiting.ii. Cause cerebral edema due to arteriolar dilationiii. Tt for Alkalosis Acetazolamide and for cerebral edema gluco-corticoidsiv. High altitude pulmonary edema is a serious form of mountain sickness pulmonary edema 