ALTERNATIVE MODES OF MECHANICAL VENTILATION

肺气体交换失败最常见的原因是肺泡灌洗 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，常规机械 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。 一个长期目标是 研究是探索创新的CMV设置及其与 连续流动通气（CFV）;另一个是获得更好的理解 CFV期间吸入气体和肺泡气体之间的不寻常气体混合，以及 这一过程如何与支气管空气动力学和 和正常肺内V/Q变化的性质。 CFV的最新研究 表现出意外的肺过度充气，与肺叶相关 充气不均匀，动脉血氧不足， 呼吸道阻力与CMV相比。 在第一系列研究中，我们 建议：a）描述和解释气体流速的影响， 在支气管模型中CFV期间对气道动力学的物理性质，以及 为了将这些测量扩展到麻醉的狗，利用逆行 导管技术; B）将观察到的气道动力学与肺 恶性通货膨胀，并探讨使用低密度气体（氦氧混合气）， 气道内连续流动射流的位置，以最小化 c）区分不完全气相 弥散或V/Q方差增加是动脉低氧血症的原因 利用应用于整个肺的多种惰性气体技术， CFV期间下叶过度充盈; d）评价新的组合 CFV与CMV的小潮气量偏移，以优化最佳 两种机械通气方式的优点。 在第二系列的 我们打算使用CFV作为实验工具来探索动物 呼吸衰竭模型。 在犬肺水肿：a）我们将使用 肺压力-容量关系的滞后性，以寻求最佳的 分流最小化时的肺泡压（Palv）; B）在恒定Palv下， 我们将把肺容量和分流的变化联系起来， 间质和肺泡空间之间的水肿再分布; c） 将这些结果与CMV进行比较，将评估循环免疫的作用。 通气对水肿分布和积聚的影响。 在犬科动物模型中 和猪气流阻塞，我们将测量 CMV期间多个惰性气体交换的支气管痉挛和气体潴留， CFV，并测试CFV的效果，以尽量减少气体捕获。 一个长期 这些研究的目的是提供更好的理解， 肺泡压、肺容量、肺气体含量之间的相互关系 交换，以及诱发疾病（水肿或支气管痉挛）。 已解析 机制提出了几个建议的替代模式的扩展， 通气到正在模拟的临床条件。

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.