RESPIRATORY PUMP FAILURE--APPLIED PHYSIOLOGY

该提案的最终目标是测试以下各项 假设：a)脱机期间高碳性呼吸衰竭 机械通风通常由隔膜引起 疲劳，以及b)隔膜疲劳是由不平衡引起的 呼吸肌上的机械负荷和他们的 忍耐力。本文介绍了三项研究。 议定书1的目的是验证隔膜的重要性 高碳性呼吸衰竭患者的病理生理学疲劳 病人。双侧膈肌对横隔膜的反应 将对呼吸机依赖患者的刺激进行评估 在失败的断奶尝试前后。横隔膜疲劳会 定义为跨膈肌抽动压力的下降 在断奶前和断奶后状态之间。结果将决定： A)疲劳发生率，以及b)疲劳是否为故障 神经肌肉传递和/或兴奋性收缩 耦合。这项研究还将提供关于以下方面的信息：a) 从疲劳中恢复所需的时间，以及b)预测 较小侵入性测量的价值，如吸气功， 吸气肌力，呼吸道阻塞压， 跨膈压(PDI)、呼吸模式、 胸腹联合运动的功率谱分析 隔膜肌电和气体交换变量。 协议2的目的是验证双边生成的PDI 以膈神经刺激为指标的大鼠膈肌收缩功能研究 一个普通人。在正常志愿者中，双侧产生的PDI 膈神经刺激将被评估为肺功能。 放松时的容量，当胸腹形状 由气动装置系统地改变，该气动装置 沿等体积线置换胸部和腹部。会的 从而确定腹部容量是否在肺内不变 体积对隔膜有显著的独立影响 功能。 第三号议定书的具体目标是确定 双侧膈神经刺激产生的PDI与 狗体内的局部横隔膜力学。要评估 PDI作为整体横隔膜功能指标的局限性， 区域隔膜功能及其与PDI的关系将是 在狗身上进行评估。通过改编视频摄影 区域肺功能研究的标记物技术 横隔膜的局部收缩能力将在体内进行评估 在定义的初始长度和载荷的条件下。

The ultimate goal of this proposal is to test the following hypotheses: a) hypercarbic respiratory failure during weaning from mechanical ventilation usually results from diaphragm fatigue, and b) diaphragm fatigue results from an imbalance between the mechanical load on the respiratory muscles and their endurance. Three studies are presented. The aim of Protocol 1 is to verify the importance of diaphragm fatigue in the pathophysiology of hypercarbic respirtory failure in patients. The response of the diaphragm to bilateral phrenic stimulations will be evaluated in ventilator-dependent patients before and after failed weaning attempts. Diaphragm fatigue will be defined as a fall in the transdiaphragmatic twitch pressure between pre and postweaning states. The results will determine: a) the incidence of fatigue, and b) whether fatigue is a failure in neuromuscular transmission and/or excitation contraction coupling. This study will also give information concerning: a) the time necessary for recovery from fatigue, and b) the predictive value of less invasive measurements such as inspiratory work, inspiratory muscle strength, airway occlusion pressure, transdiaphragmatic pressure (PDI), breathing pattern, thoracoabdominal motion, the power spectral analysis of the diaphragm EMG, and gas exchange variables. The aim of Protocol 2 is to validate PDI generated by bilateral phrenic stimulation as an index of diaphragm contractility in normal man. In normal volunteers, PDI produced by bilateral phrenic nerve stimulation will be evaluated as a function of lung volume during relaxation and while thoracoabdominal shape is being systematically altered by a pneumatic device which displaces the thorax and abdomen along an isovolume line. It will thus be determined whether abdominal volume at a constant lung volume has a significant independent effect on diaphragm function. The specific aim of Protocol 3 is to determine the relationship between PDI generated by bilateral phrenic stimulation and regional diaphragm mechanics in the dog. To assess the limitations of PDI as an index of global diaphragm function, regional diaphragm function and its relationship to PDI will be evaluated in the dog. By adapting the videoroentgenographic marker technique for studying regional lung function to the diaphragm, the regional contractility will be evaluated in vivo under conditions of defined initial lengths and loads.