Physiology Cases a...
Case 20
Case
Dan Hsieh celebrated his graduation from college by joining a mountain climbing expedition in the Swiss Alps. Dan is in excellent physical condition: he runs 3-5 miles daily, and he played intramural soccer, volleyball, and rugby throughout college. At the insistence of his parents, Dan underwent a complete medical examination before the climb, which he passed with flying colors. He was off to the Alps!
QUESTIONS
1. Mont Blanc, the highest elevation in the Swiss Alps, is 15,771 feet above sea level. The barometric pressure on Mont Blanc is approximately 420 mm Hg. (The barometric pressure at sea level is 760 mm Hg.) What is the fractional concentration of O2 (FiO2) in atmospheric air on Mont Blanc? What is the partial pressure of oxygen (PO2) of humidified air on Mont Blanc? How does this value of PO2 compare with the PO2 of humidified air at sea level?
2. At his physical examination (performed at sea level), Dan's arterial PO2 (PaO2) was 100 mm Hg. If Dan's PaO2 had been measured when he arrived on Mont Blanc, it would have been approximately 50 mm Hg. Why would his PaO2 be decreased at the higher elevation? What was Dan's alveolar PO2 (PAO2) on Mont Blanc?
3. Predict whether each of the following parameters would be increased, decreased, or unchanged on Mont Blanc. Explain why each of the predicted changes would occur.
a. Breathing rate
b. Percent saturation of hemoglobin
c. PO2 at which hemoglobin is 50% saturated (P50)
d. Pulmonary artery pressure
