Brown R H, Mitzner W
Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21205, USA.
Am J Respir Crit Care Med. 2000 Dec;162(6):2113-6. doi: 10.1164/ajrccm.162.6.2004055.
A deep inspiratory sigh is one of the most severe dynamic stresses that lungs normally experience. It typically is a very transient phenomenon, normally lasting only about 2 to 3 s. The airway response to a deep inspiration has been shown to be different in asthmatic and normal individuals. When airway smooth muscle (ASM) is contracted in normal subjects, a deep inspiration results in a subsequent dilation of the airways. However, in asthmatic subjects, a deep inspiration often results in little change in airway function, and sometimes results in an even further contraction of ASM. The mechanism underlying this difference depends on the dynamic behavior of both ASM and the lung parenchyma. If the contracted muscle had slower dynamic responses than the lung parenchyma, the timing of the deep inspiratory maneuver could affect the airway response. In the present study, we designed an experiment to determine how well matched the dynamic response is of airways to that of the lung parenchyma. The results clearly demonstrate that airways contracted with methacholine dilate at about a rate four times slower than that of the lung parenchyma during rapid lung inflation and deflation. This effect may play a role in the unique response of asthmatic subjects to deep inspiration. The mechanism of this dynamic slowness of contracted airways probably involves intrinsic properties of the smooth-muscle contractile processes.
深吸气叹息是肺部正常情况下所经历的最强烈的动态应激之一。它通常是一种非常短暂的现象，通常仅持续约2至3秒。哮喘患者和正常人对深吸气的气道反应已被证明有所不同。在正常受试者中，当气道平滑肌（ASM）收缩时，深吸气会导致随后气道扩张。然而，在哮喘患者中，深吸气通常导致气道功能变化很小，有时甚至会导致ASM进一步收缩。这种差异背后的机制取决于ASM和肺实质的动态行为。如果收缩的肌肉比肺实质具有更慢的动态反应，深吸气动作的时机可能会影响气道反应。在本研究中，我们设计了一项实验来确定气道与肺实质的动态反应匹配程度如何。结果清楚地表明，在快速肺膨胀和收缩过程中，用乙酰甲胆碱收缩的气道扩张速度比肺实质慢约四倍。这种效应可能在哮喘患者对深吸气的独特反应中起作用。收缩气道这种动态迟缓的机制可能涉及平滑肌收缩过程的内在特性。
