While static mechanical forces govern resting lung volumes, dynamic forces determine tidal breathing, airflow, and changes in airflow and lung volume during normal and abnormal breathing. This section will examine the mechanisms, measurement methodology, and interpretation of the dynamic changes in airflow and lung volume that occur in health and disease. We will first examine how the total work of breathing can be described by the parameters of the equation of motion, which determine the pressure required to move air into and out of the lung. This will include a detailed description of airflow characteristics and airway resistance. Next, we will review the changes in pressure and flow that determine maximal forced inspiration and expiration, which result in the maximal flow–volume loop and the clinically important forced expired volume in 1 second. We will also assess the mechanisms and interpretation of bronchodilator responsiveness, dynamic hyperinflation, and airways hyperresponsiveness.

静态机械力控制静息肺容积，而动态力决定潮式呼吸、气流以及正常和异常呼吸期间气流和肺容积的变化。本节将研究健康和疾病中气流和肺容量动态变化的机制、测量方法和解释。我们将首先研究如何通过运动方程的参数来描述呼吸的总做功，运动方程确定将空气移入和移出肺部所需的压力。这将包括气流特性和气道阻力的详细描述。接下来，我们将回顾决定最大用力吸气和呼气的压力和流量变化，从而产生最大流量-容量环和 1 秒内临床上重要的用力呼气量。我们还将评估支气管扩张剂反应性、动态过度充气和气道高反应性的机制和解释。