Pulmonary gas exchange, diffusion and intra-pulmonary arteriovenous shunting during physiological stress

运动代表了对肺系统的压力，以维持足够的肺气体交换。随着运动量的增加，肺弥散能力必须增加，以满足增加的氧气需求，并防止扩散限制。运动时弥散能力（DLCO）的增加是通过肺毛细血管募集和毛细血管扩张来实现的，这导致肺毛细血管血容量（Vc）和弥散膜容量（Dm）两者的增加。尽管DLCO随着运动而增加，但大多数健康人的肺气体交换受损，其量化为肺泡与动脉PO2差异（AaDO2）的增加，我们的小组先前提供的证据表明，运动导致的AaDO2增加可能是由于解剖学肺内动静脉分流（IPAVA）的募集。

Exercise represents a stress to the pulmonary system to maintain adequate pulmonary gas exchange. With incremental exercise, pulmonary diffusing capacity must increase to meet the increased oxygen demand, and prevent a diffusion limitation. The increase in diffusing capacity (DLCO) with exercise is accomplished by pulmonary capillary recruitment and capillary distention which results in an increase in both pulmonary capillary blood volume (Vc) and diffusing membrane capacity (Dm). Despite an increase in DLCO with exercise, most healthy humans develop an impairment in pulmonary gas exchange as quantified by an increase in the alveolar to arterial PO2 difference (AaDO2), and our group has previously provided evidence that the increased AaDO2 with exercise may be due to the recruitment of anatomical intra-pulmonary arteriovenous shunts (IPAVAs).