Eldridge F L, Vaughn K Z
J Appl Physiol Respir Environ Exerc Physiol. 1977 Aug;43(2):312-21. doi: 10.1152/jappl.1977.43.2.312.
The occluded airway pressure generated by contraction of inspiratory muscles was measured in spontaneously breathing, anesthetized, vagotomized cats at thoracic volumes below, at, and above true FRC (range, -8 to +28 ml/kg). A relatively constant neural drive at all volumes was shown by recordings of integrated phrenic nerve and external intercostal muscle activities. Peak occlusion pressure declined progressively with increasing thoracic volume and increased with occlusion volumes below FRC. Occlusion pressures measured early in inspiration (0.3 and 0.5 s) decreased similarly. Since occluded airway pressure was a satisfactory index of muscle force output of all inspiratory muscles, the study demonstrates that inspiratory muscle performance decreases with increasing thoracic volume throughout the range studied. Analysis of all occluded breaths shows that, quantitatively, the decline in muscle performance from that occurring at true FRC was -1.9% per ml/kg volume change from FRC. Zero effective muscle pressure generation occurred at 52 ml/kg above FRC, or 2.8 times FRC. These findings have important implications for the use of occlusion pressures and ventilatory responses in respiratory control system studies, since changes in FRC may affect muscle performance.
在自主呼吸、麻醉且切断迷走神经的猫身上，测量了吸气肌收缩产生的气道阻塞压力，测量时胸廓容积低于、等于和高于真功能残气量（范围为-8至+28毫升/千克）。通过膈神经和肋间外肌活动的积分记录表明，在所有容积下神经驱动相对恒定。随着胸廓容积增加，峰值阻塞压力逐渐下降，而在功能残气量以下的阻塞容积时则升高。在吸气早期（0.3秒和0.5秒）测量的阻塞压力也有类似下降。由于气道阻塞压力是所有吸气肌肌肉力量输出的一个满意指标，该研究表明，在所研究的整个范围内，吸气肌性能随胸廓容积增加而下降。对所有阻塞呼吸的分析表明，从数量上看，相对于在真功能残气量时的肌肉性能，每毫升/千克容积从功能残气量变化时，肌肉性能下降1.9%。在高于功能残气量52毫升/千克或功能残气量的2.8倍时，有效肌肉压力产生为零。这些发现对呼吸控制系统研究中阻塞压力和通气反应的使用具有重要意义，因为功能残气量的变化可能影响肌肉性能。
