ALTERNATIVE MODES OF MECHANICAL VENTILATION

我们研究不同的机械通风模式的目标 就是评估机械通风的策略 在向全身组织最佳输送氧气的同时 招致的不良影响最小。(A)正常肺，(B) 肺水肿；及(C)急性气流阻塞的肺部 由支气管痉挛引起的，我们将使用和评估非常规 机械通风的方式。建议的替代模式 包括高频振荡通风 (HFOV)、持续流动通风(CFV)和体外循环 膜氧合(ECMO)，单独或与 某种形式的常规机械通风(CMV)。三 提出了几组实验：(一)机构的评价 CFV和HFOV过程中的气相传质特性。这些 在麻醉的狗和猪身上进行的实验， 肺水肿性或支气管性狭窄，或在硬性呼吸道 模型，将确定气体在呼吸道内混合的机制 在不同的气道世代和在不同的平行路径之间，以及 将把这些流动模式与气体传输效率联系起来。这些 实验应该确定总体调整的策略 肺泡通气量及其区域间的一致性。(Ii) 在第二组实验中，我们将应用这些替代方案 两种急性低氧血症模型的机械通气方式 呼吸衰竭或支气管收缩以维持气体 交流，最大限度地减少不良影响。在这方面，我们要求四个 问题：1)在相同的平均牙槽压下，如何 通过水肿液的最佳再分配最大限度地提高氧合 (肺部水肿性)或通过调整呼吸模式 (支气管痉挛)？2)平均和最高胸腔内压 以任何给定的通风模式单独或组合减少， 这种减少是否改善了心输出量和全身氧合 分娩？3)周期性肺泡压力波动是如何 影响水肿堆积和清除？4)循环 应用高肺泡压力可进一步加重肺损伤，并可 机械通风的替代模式减少了这种额外的 短期或长期的损害？(三)在处理两个问题时 上面详述的广泛问题，我们应该学习如何最好地 机械通气在低压性肺水肿中的应用 处于哮喘状态的患者。在第三组实验中， 我们的长期目标是评估这些方法在临床上的应用 在危重病人身上的试验。在此过程中，我们将评估 基础气体交换和血流动力学异常在 急性低氧性呼吸衰竭，然后测试各种方式 以早期动物研究结果为指导的方法。

Our goal in studying Alternative Modes of Mechanical Ventilation is to evaluate strategies of mechanical ventilation which result in the optimal delivery of oxygen to systemic tissues while incurring the minimum adverse effects. In (a) normal lungs, (b) in pulmonary edema, and (c) in lungs with acute airflow obstruction caused by bronchospasm, we will employ and evaluate nonconventional modes of mechanical ventilation. The proposed alternative modes of ventilation include high frequency oscillatory ventilation (HFOV), continuous flow ventilation CFV), and extra-corporeal membrane oxygenation (ECMO), either alone or in combination with some form of conventional mechanical ventilation (CMV). Three groups of experiments are proposed (i) Evaluation of the mechanisms of gas phase mass transport during CFV and HFOV. These experiments, performed in anesthetized dogs and pigs with normal, edematous, or bronchoconstricted lungs, or in hardware airway models, will identify mechanisms of gas mixing within the airways at various airway generations and among various parallel paths, and will relate these flow patterns to gas transport efficiency. These experiments should identify strategies for adjusting overall alveolar ventilation as well as its uniformity among regions. (ii) In the second group of experiments, we will apply these alternative ventilation modalities in models of either acute hypoxemic respiratory failure or bronchoconstriction in order to maintain gas exchange and minimize adverse effect. In this regard we ask four questions: 1) At the same mean alveolar pressure, how can oxygenation be maximized by optimal redistribution of edema fluid (edematous lungs) or by adjustment of ventilatory mode (bronchospasm)? 2) Can mean and peak intrathoracic pressures be reduced with any given ventilatory mode alone or in combination, and does this reduction improve cardiac output and systemic oxygen delivery? 3) How does cyclic alveolar pressure fluctuation influence edema accumulation and clearance? 4) Does cyclic application of high alveolar pressures further lung injury, and can alternative modes of mechanical ventilation abate such additional damage in the short or long term? (iii) In addressing the two broad issues detailed above we should have learned how best to apply mechanical ventilation in low pressure pulmonary edema or in patients in status asthmaticus. In the third group of experiments, our long range goal is to evaluate these approaches in clinical trials in acutely ill patients. In doing so we will evaluate the fundamental gas exchange and hemodynamic abnormalities manifest in acute hypoxemic respiratory failure, then test various modalities in an approach directed by results of earlier animal studies.