Question

Case Study Questions

Robert Hines celebrated his graduation from college by going to Alaska for some climbing. Robert is in excellent physical condition: he runs 5 miles daily, played intramural spikeball, and was a volunteer firefighter. Because his parents are obligated to pay his private student loans after his death, they had Robert undergo a complete medical examination before climbing Mount Vancouver.

Mount Vancouver has its southern side in Glacier Bay National Park and Preserve in Alaska and its northern side in Kluane National Park and Reserve in Canada. You plan to climb the mountain to take advantage of the local duty-free shop on the Canadian side. The summit is approximately 15,787 feet above sea level, and the barometric pressure is around 420 mm Hg (sea level is 760 mm Hg).

1. What is the fractional concentration of O2 (FIO2) in atmospheric air on Mount Vancouver? What is the partial pressure of oxygen (Po2) of humidified air on Mount Vancouver? 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), Roberts’s arterial Po2 (PaO2) was 100 mm Hg. If Robert’s PAO2 had been measured when he arrived on Mount Vancouver, it would have been approximately 50 mm Hg. Why would his PAO2 be decreased at the higher elevation? What was Robert’s alveolar Po2 (PaCO2) on Mount Vancouver?

3. Predict whether each of the following parameters would be increased, decreased, or unchanged on Mount Vancouver. 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

4. If Robert’s arterial Pco2 (PaCO2) had been measured on Mount Vancouver, would it have been increased, decreased, or unchanged compared with normal? Why? If you predicted a change in PaCO2, what effect would this change have had on arterial pH? What acid–base disorder would it have caused?

5. Robert was encouraged to breathe from tanks of 100% O2. What is the Po2 of 100% humidified O2 on Mount Vancouver? What effect would breathing 100% O2 have had on Robert’s PaO2? What effect would it have had on his breathing rate?

6. The physician suggested that Robert take acetazolamide, a carbonic anhydrase inhibitor, prophylactically. Which of the responses and changes that you predicted in Questions 3 and 4 would have been eliminated or offset if Robert took acetazolamide?

Answer 1

1)fio2 represent the oxygen present in inspired air

Oxygen amount present in total air is 21%

So Fio2 = 0.21

Rest Po2 at mountain and how it is differ from at see level is described below

at sea level barometre Pressure 76ony - totar barometre Bressue in Gomma pa on mount vonoh & 2 760 a 966treet Por at relateret 2 X760 159.9 rashe ta -arant & q in dira 21.1. a. Per vane on mount vancover Por at sea level

2) as we move to altitude, barometric pressure decreases ( 760 mmHg at sea level, mount 470 mmHg) ,

So as calculated above pO2 is less than sea pressure. So tere will be less difference in partial pressure of o2 in air as compared to alveolar air . Less gaseous exchange at mountain level lead to pO2 at higher elevations level.

3) brehing rate- breathing rate increased, due to decrease Po2 , less oxygen will be taken in and lead to compensatory increase in breathing rate

Percent saturation of Hb- decreased,  

Saturation of Hb depends on partial pressure of oxygen. As partial pressure of oxygen decreased, lead to decreased percentage saturation of Hb.

Po2 at which Hb will get 50% saturated- increased, due to decreased pO2 at mountain.

Pulmonary artery pressure- decreased, due to decrease partial pressure of o2.