Question

If someone inhales a mixture of 50% oxygen(the partial pressure of oxygen in the mixture is 380mmHg)at sea level at an alveolar ventilation rate of 5L/min and this person is exercising and their body is consuming 1000mLO2/min,what will be the partial pressure of oxygen in the gas that they exhale?

Answer 1

Solution.

The total pressure is related to a partial pressure as

,

As the mixture contains 50% of oxygen, and it correcponds to a pressure of 380 mmHg, the total pressure is 380*2 = 760 mmHg.

The person lungs ventilate 5 L/min of a mixture, which contains 5*0.5 = 2.5 L/min of oxygen and 2.5 L of other gases.The consumption of oxygen is 1 L/min, so 2.5-1 = 1.5 L/min fo oxygen remains unused and exhales.

The other gases are not consumable, so they exhale unchanged, with a rate of 2.5 L/min. The volume of each gas is proportional to the amount of substance and to a partial pressure. The total pressure is keeping the same - 760 mmHg, so the partial pressure of oxygen in exhaling gases is: