Passage VI
In the human body, O2 and CO2 are exchanged between the lungs and the blood and between the blood and the tissues as indicated in Figure 1. These exchanges occur by the diffusion of each gas from a region where its partial pressure (the pressure contributed by a single gas) is higher to a region where its partial pressure is lower. The figure gives the partial pressures PO2 and PCO2 in the lung alveoli (sacs), in the tissue cells, and in the blood of a healthy resting person at sea level.
Figure 2 shows how alveolar PO2 and PCO2 vary with alveolar ventilation (volume of air per unit time available to the alveoli for gas exchange).
Figures adapted from Arthur J. Vander, James H. Sherman, and Dorothy S. Luciano, Human Physiology: The Mechanisms of Body Function. ©1985 by McGraw-Hill, Inc.
39. Consider the values of PO2 and PCO2 that are given in Figure 1 for the lung alveoli. According to Figure 2, to maintain those values, alveolar ventilation must be closest to which of the following?
Your Answer is
Correct Answer is B
Explanation
In Figure 1, PO2=104, PCO2=40, corresponding to the value in Figure 2 whose abscissa is about 4.2, choose B