The pulmonary circulation:

C. Supplies the metabolic needs of the alveoli.

 DISCUSSION: Pulmonary artery circulation transports oxygenated blood to the alveoli level where gas exchange occurs, and it is here that the matching of ventilation and perfusion is so important during the postoperative period. The loss of lung volume that generally occurs after all surgical procedures does not return to baseline for 5 to 7 days and may play an important role in the ventilation-perfusion ratio. Improving or returning lung volume to normal is performed by manipulating functional residual capacity (FRC) and preventing atelectasis, which in turn maintains circulation to the alveolus and optimizes the ventilation-perfusion ratio.