At the altitude of 6500 meters, the atmospheric pressure is 347 Hg. What is the inspired PO2?: (A) 73 mmHg, (B) 63 mmHg, (C) 53 mmHg, (D) 83 mmHg
Answer is A. PO2 of the inspired air is 21 percent of ihe total barometric (atmospheric) pressure. Hence, (21/100) 347 = 72.87. Decreased ambient oxygen pressure results in hypoxemia. This is most commonly seen at high altitude or in nonobstructive asphyxia. The A-a O2 gradient is normal, and hypoxemia improves with supplemental oxygen. Ref: Sarko J., Stapczynski J.S. (2011). Chapter 65. Respiratory Distress. In J.E. Tintinalli, J.S. Stapczynski, D.M. Cline, O.J. Ma, R.K. Cydulka, G.D. Meckler (Eds), Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 7e.