Chapter 19, Problem 1RQ

The barometric pressure is about half the sea-level value of 760 mm Hg at an altitude of

4,000-5,000 feet

9,000-10,000 feet

14,000-15000 feet

18,000-19,000 feet

Summary Introduction

Introduction:

The functioning of the cardiac and pulmonary system is affected by the high altitude. The atmospheric pressure progressively decreases with the altitude. Henry’s law states that the solubility of a gas is directly proportional to the partial pressure of the gas. The decrease in the air pressure at high altitude makes the air deprived of oxygen and that leads to different abnormalities of the cardiac or pulmonary system. The people living in the mountains and at other high altitude places generally face this issue of altitude sickness.

Answer to Problem 1RQ

Correct answer:

18,000-19,000 feet.

Explanation of Solution

Justification/ Explanation for the correct answer:

Option (d) is 18,000 to 19,000 feet. The pressure decreases with altitude, under normal conditions and the barometric pressure reduces to about half of the pressure at sea level, at an altitude of 18,000-19,000 feet. The sea level barometric pressure value is 760 mm Hg and it becomes 380 mm Hg at height 18,000-19,000 feet. Hence, option (d) is correct.

The explanation for the incorrect answers:

Option (a) is 4,000 to 5,000 feet. The pressure value reaches to half at an altitude of 18,000 to 19,000 feet. The value of barometric pressure decreases with the altitude and this causes altitude sickness in the persons traveling to high altitude. So, it is an incorrect option.

Option (b) is 9,000 to 10,000 feet. The barometric pressure reduces to half when the height is about 18,000 to 19,000 feet. The persons living constantly at high altitude places are adapted to this environment because due to low pressure the air becomes deprived of oxygen and the body thus uses several mechanisms to deal with the conditions. So, it is an incorrect option.

Option (c) is 14,000 to 15,000 feet. The barometric pressure reduces to half at an altitude of 18,000 to 19,000 feet. The body deals with this decreased pressure by increasing the total number of red blood cells and the amount of hemoglobin. This phenomenon occurs in those who climb to altitudes of more than 18,000 feet or have to live constantly at high altitude. So, it is an incorrect option.

Hence, options (a), (b), and (c) are incorrect.

Conclusion

The barometric pressure decrease to half the value at sea level at an altitude of 18,000 to 19,000 feet. The barometric pressure value at sea level is 760 mm Hg and at height 18,000-19,000 feet, it becomes 380 mm Hg.