Ventilator-induced diaphragm dysfunction

描述（由申请人提供）：最近对大鼠的研究表明，长时间（即bb0 - 12小时）机械通气（MV）与膈肌不活动相关，会导致膈肌力产生明显下降。如果这种疾病也发生在MV的人身上，它可以解释一些患者难以停止MV（即断奶困难）以及一些不能从MV中断奶的患者。大鼠研究表明：(a)氧化应激，(b)蛋白水解增加，(c)长时间MV（即PMV）暴露的大鼠膈肌纤维发生萎缩。我们对循环完整的PMV脑死亡器官供体的初步观察表明，这种疾病也可能发生在人类身上。在拟建的研究中，我们将进行配对病例对照研究，以回答以下问题：(1)暴露于PMV的人类是否会发生类似的疾病？(2) PMV在人横膈膜中产生什么病理？我们将脑死亡器官捐赠者定义为具有以下特征的病例：(a) MV≥12小时但<72小时；(b)在MV停止前立即进行横膈膜活检；(c)无感染。我们将匹配对照定义为：(a)年龄相同- 5岁的孤立性肺结节（SPN）患者；(b)同性；(c)术中膈肌活检前<3小时接受神经肌肉阻滞剂；(d) SPN病理显示为良性病变；(e)无感染。我们之前的研究表明，对照组没有出现横膈膜病理。因此，我们将通过比较每一对配对的病例和对照来检验我们的每一个假设。需要验证的具体假设是，与对照相比，病例表明：(a)氧化应激表现为蛋白质羰基化和蛋白质酪氨酸硝化增加；(b)单渗透纤维中肌球蛋白重链和肌钙蛋白的比力降低，钙敏感性降低；(c)由于钙蛋白酶活性和泛素蛋白结合的上调，蛋白质水解增加；(d)肌纤维萎缩（约25-30%）和(e)计算最大膈肌力产生明显下降。对于这些变化，我们详细的蛋白质组学，基因组学，生理学和组织学研究将提供一个机制的解释。总之，这些研究可能定义了一种非常普遍的新隔膜疾病，严重降低了我们患者的生活质量，也消耗了我们有限的医疗资金。此外，这些研究可能直接导致隔膜肌这种新认识但相对常见的疾病的治疗。

DESCRIPTION (provided by applicant): Recent studies in rats demonstrate that prolonged (i.e., >12 hours) mechanical ventilation (MV) associated with diaphragm inactivity elicit marked decreases in diaphragm force generation. If this disorder also occurs in humans on MV, it could explain the difficulty in discontinuing MV in some patients (i.e., difficulty in weaning) as well as for some patients who can not be weaned from MV. The rat studies indicate that a combination of (a) oxidative stress, (b) increased proteolysis, and (c) atrophy occur in diaphragm myofibers of rats exposed to prolonged MV (i.e., PMV). Our preliminary observations on PMV brain-dead organ donors with an intact circulation suggest that this disorder may also occur in humans. In the proposed research, we will carry out a matched pair case control study to answer the following questions: (1) Does a similar disorder occur in humans exposed to PMV? and (2) What pathology is produced by PMV in the human diaphragm? We define a case as a brain dead organ donor who has the following attributes: (a) on MV for >12 hours but <72 hours; (b) undergoes a diaphragm biopsy immediately before cessation of MV; and (c) absence of infection. We define a matched control as a patient with a solitary pulmonary nodule (SPN) that is (a) the same age ¿5 years; (b) same gender; (c) receives neuromuscular blocking agents <3 hours before intra- operative diaphragm biopsy; (d) pathology on SPN shows benign disease; and (e) absence of infection. We have previously shown that controls exhibit no diaphragm pathology. Therefore, we will test each of our hypotheses by comparing cases and controls of each matched pair. The specific hypotheses to be tested are that in comparison to controls, cases show: (a) oxidative stress manifest by increased protein carbonylation and increased protein tyrosine nitration; (b) decreased specific force and decreased calcium sensitivity of force generation in myosin heavy chain and troponin characterized single permeabilzed fibers; (c) increased proteolysis due to an up-regulation of calpain activity and ubiquitin-protein conjugation; (d) myofiber atrophy (approximately 25-30%) and (e) marked decreases in computed maximum diaphragm force generation. For each of these changes, our detailed proteomic, genomic, physiological and histological studies will provide a mechanistic interpretation. In conclusion, these studies may define a new diaphragm disorder that is quite prevalent, causes severely decreased quality of life for our patients, and also is very costly for our limited health care funds. Moreover, these studies may directly lead to therapy for this newly recognized but relatively common disease of diaphragm muscle.