Zach M S
Respiratory and Allergic Disease Division, Paediatric Department, University of Graz, Austria.
Paediatr Respir Rev. 2000 Mar;1(1):36-9. doi: 10.1053/prrv.2000.0010.
Insight into the physiology of a forced expiration is the most important prerequisite for understanding and correctly interpreting the most common pulmonary function tests like spirometry and recording of a maximum expiratory flow-volume curve. Along the airway, intraluminal pressure falls progressively from alveolar pressure in the periphery to atmospheric pressure at the airway opening. Downstream of the equal pressure point, where intraluminal equals transthoracic pressure, the airway is dynamically compressed. Once the forced expiration is flow limited, more transthoracic pressure will rather effect more compression than a further increase in flow. It follows that the achieved maximum expiratory flow rates are then exclusively defined by the resistance of the intrathoracic airways and no longer by muscular effort. The end of a forced expiration is determined by the elastic resistance of the thoracic cage and by airway closure.
深入了解用力呼气的生理学是理解和正确解读最常见的肺功能测试（如肺活量测定和最大呼气流量-容积曲线记录）的最重要前提。沿着气道，管腔内压力从外周的肺泡压力逐渐下降到气道开口处的大气压。在等压点下游，即管腔内压力等于跨胸壁压力处，气道会受到动态压缩。一旦用力呼气出现流量受限，更多的跨胸壁压力会导致更多的压缩，而不是使流量进一步增加。因此，所达到的最大呼气流量率仅由胸内气道的阻力决定，而不再由肌肉力量决定。用力呼气的结束由胸廓的弹性阻力和气道关闭决定。
