ALTERNATIVE MODES OF MECHANICAL VENTILATION

肺气体交换失败最常见的原因是肺泡充盈 疾病，如肺水肿，或急性气流阻塞，如 哮喘持续状态。 在这两种情况下，传统的机械 通气（CMV）与严重并发症相关，尤其是 气压伤和心输出量减少。 这其中的一个长期目标 研究旨在探索 CMV 的创新设置及其与 连续流通气（CFV）；另一个是获得更多的了解 CFV 期间吸入气体和肺泡气体之间不寻常的气体混合，以及 这个过程如何与支气管空气动力学和场地联系起来 以及正常肺内 V/Q 方差的性质。 CFV的最新研究 证明与肺叶相关的意外肺部过度充气 充气不均匀、动脉低氧血症和 4-5 倍增加 气道阻力与 CMV 相比。 在第一个系列的研究中，我们 建议：a) 描述和解释气体流量和 支气管模型 CFV 期间气道动力学的物理特性，以及 将这些测量扩展到麻醉狗，利用逆行 导管技术； b) 将观察到的气道动力学与肺联系起来 恶性通货膨胀，并探索使用低密度气体（氦氧）和 连续流射流在气道内的位置，以尽量减少 肺叶不均匀性； c) 区分气相是否不完全 扩散或 V/Q 方差增加是动脉低氧血症的原因 利用应用于整个肺部的多重惰性气体技术 CFV 期间下叶过度膨胀； d) 评估新的组合 CFV 与 CMV 小潮气量偏移相结合，以优化最佳方案 两种机械通气形式的优点。 在第二个系列中 我们打算使用CFV作为实验工具来探索动物的研究 呼吸衰竭模型。 对于犬肺水肿：a) 我们将使用 肺压力-容积关系的滞后性，寻求最佳值 分流最小化时的肺泡压（Palv）； b) 在常数Palv下， 我们将把肺容量和分流的变化联系起来，以推断出 间质和肺泡空间之间的水肿重新分布； c) 将这些结果与 CMV 进行比较将评估循环的作用 通气对水肿分布和积累的影响。 在犬科动物模型中 和猪气流阻塞，我们将测量以下因素的影响 CMV 和 CMV 期间多次惰性气体交换的支气管痉挛和气体捕获 CFV，并测试 CFV 最大限度地减少气体滞留的效果。 一个长期的 这些研究的目的是为了更好地了解 肺泡压、肺容量、肺气体之间的相互关系 交换和诱发疾病（水肿或支气管痉挛）。 所阐明的 机制提出了几种替代模式的扩展建议 通气适应正在建模的临床状况。

Failure of pulmonary gas exchange is most commonly due to alveolar flooding diseases as in pulmonary edema, or to acute airflow obstruction, as in status asthmaticus. In both conditions, conventional mechanical ventilation (CMV) is associated with significant complications, especially barotrauma and reduction of cardiac output. One long-term goal of this study is to explore innovative settings of CMV and its combination with continuous flow ventilation (CFV); another is to gain greater understanding of the unusual gas mixing between inspired and alveolar gas during CFV, and how this process might be linked to bronchial aerodynamics and to the site and nature of the V/Q variance within normal lungs. Recent studies of CFV demonstrate unexpected hyperinflation of the lungs, associated with lobar inhomogeneity of inflation, arterial hypoxemia, and 4-5 fold increases in airways resistance compared to CMV. In a first series of studies, we propose: a) to describe and explain the effects of gas flow rate and physical properties on airway dynamics during CFV in a bronchial model, and to extend these measurements to the anesthetized dog, utilizing retrograde catheter techniques; b) to relate the observed airways dynamics to lung hyperinflation, and to explore the use of low density gas (heliox) and position of the continuous flow jets within the airway to minimize the lobar inhomogeneity; c) to distinguish whether incomplete gas phase diffusion or increased V/Q variance is the cause of arterial hypoxemia utilizing the multiple inert gas technique applied to the whole lung and to the hyperinflated lower lobes during CFV; d) to evaluate newer combinations of CFV with small tidal volume excursions of CMV to optimize the best advantages of both forms of mechanical ventilation. In a second series of studies we intend to use CFV as an experimental tool to explore animal models of respiratory failure. In canine pulmonary edema: a) we will use the hysteresis of the lung pressure-volume relationship to seek the optimal alveolar pressure (Palv) at which shunt is minimized; b) at constant Palv, we will relate changes in lung volume and shunt to deduce mechanisms of edema redistribution between interstitial and alveolar spaces; c) comparison of these results with CMV will assess the role of cyclic ventilation on edema distribution and accumulation. In models of canine and porcine airflow obstruction, we will measure the effects of bronchospasm and gas trapping on multiple inert gas exchange during CMV and CFV, and test the effect of CFV to minimize gas trapping. One long-term objective of these studies is to provide greater understanding concerning the interrelationships among alveolar pressure, lung volume, pulmonary gas exchange, and the inciting disease (edema or bronchospasm). The elucidated mechanisms suggest several proposed extensions of alternative modes of ventilation to the clinical conditions being modelled.