Melville G N, Iravani J, Richter H G
Respiration. 1978;35(1):22-9. doi: 10.1159/000193855.
Pressures at which the peripheral airways (PA) and terminal bronchioles (TB), open and closed, were studied in rats' lungs in vitro. Airway luminal diameter was directly measured at diminishing transbronchial pressure (closing) and increasing transbronchial pressure (opening) by means of a stereomicroscope with a calibrated eyepiece. The PA and TB had internal diameters at 100 mm H2O ranging from 173 to 306 micrometer and 122 to 204 micrometer, respectively. Most of the airways closed suddenly in the pressure range between 75 and 5 mm H2O and only a few were still open at zero pressure. Closure began in the distal portion of the PA and mid-portion of the TB usually in a concentric manner. Terminal bronchioles and PA that initially were prepared at room temperature instead of at 0 degrees C often contained air at zero pressure and showed a decreased response to acetylcholine. Subthreshold concentrations of acetylcholine increased the critical closing pressure by more than 100%. The critical opening pressure was considerably higher than the corresponding closing pressure. It is proposed that bronchiolar closure depends on the tone of the airway smooth muscle, the elasticity of the airway wall and probably on the surface tension of the liquid lining the mucosal membrane.
在体外研究大鼠肺中周围气道（PA）和终末细支气管（TB）开放和关闭时的压力。通过带有校准目镜的体视显微镜，在降低跨支气管压力（关闭）和增加跨支气管压力（开放）时直接测量气道管腔直径。PA和TB在100 mm H2O时的内径分别为173至306微米和122至204微米。大多数气道在75至5 mm H2O的压力范围内突然关闭，只有少数在零压力时仍开放。关闭通常从PA的远端部分和TB的中部开始，呈同心方式。最初在室温而非0℃下制备的终末细支气管和PA在零压力时通常含有空气，并且对乙酰胆碱的反应降低。亚阈值浓度的乙酰胆碱使临界关闭压力增加超过100%。临界开放压力明显高于相应的关闭压力。有人提出细支气管关闭取决于气道平滑肌的张力、气道壁的弹性以及可能取决于衬于黏膜的液体的表面张力。
