RESPIRATORY PUMP FAILURE--APPLIED PHYSIOLOGY

本提案的最终目标是测试以下内容 假设：a）断乳期间的高碳水化合物呼吸衰竭 机械通气通常是由隔膜引起的 疲劳，以及B）隔膜疲劳由不平衡引起 呼吸肌的机械负荷和 耐力 提出了三项研究。 协议1的目的是验证隔膜的重要性 疲劳在高碳酸血症性心力衰竭的病理生理学中的作用 患者 膈肌对双侧膈神经刺激的反应 将在呼吸机依赖患者中评价刺激 在尝试断奶失败之前和之后。 横膈膜疲劳将 定义为经颅肌颤搐压力下降 断奶前和断奶后的状态。 结果将决定： a）疲劳的发生率，和B）疲劳是否是 神经肌肉传递和/或兴奋收缩 偶合器. 这项研究还将提供以下方面的资料： 从疲劳中恢复所需的时间，和B）预测的 低侵入性测量值，如吸气功， 吸气肌肉力量，气道阻塞压力， 经颅压（PDI），呼吸模式， 胸腹运动，功率谱分析， 隔膜肌电图和气体交换变量。 协议2的目的是验证通过双侧 膈神经刺激作为膈肌收缩性的指标， 正常人。在正常志愿者中，双侧产生的PDI 膈神经刺激将作为肺功能进行评价 放松时的体积，而胸腹形状是 通过气动装置系统地改变， 使胸部和腹部沿等体积线沿着移动。 它将 因此可以确定在恒定的肺容量下 体积对横膈膜有显著的独立影响 功能 议定书3的具体目的是确定 双侧膈神经刺激产生的PDI与 狗的局部横膈膜力学 评估 PDI作为整体膈肌功能指标的局限性， 区域隔膜功能及其与PDI的关系将被 在狗身上评估。 通过调整录像 研究局部肺功能的标记技术 隔膜，将在体内评价局部收缩性 在限定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.