ALTERNATIVE MODES OF MECHANICAL VENTILATION

肺内气体交换失败最常见的原因是肺泡积水。 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，传统机械 机械通气(CMV)与严重的并发症有关，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 持续流动通风(CFV)；另一个是获得更多的了解 在CFV过程中吸入气体和肺泡气体之间的异常混合，以及 这一过程可能如何与支气管空气动力学和部位有关 以及正常肺内V/Q变化的性质。CFV的研究近况 表现出与肺叶相关的意外的肺过度充气 通货膨胀的不均一性、动脉低氧血症以及4-5倍的增加 与CMV相比，航空公司的阻力。在第一系列研究中，我们 建议：a)描述和解释气体流量和 在支气管模型中CFV期间的呼吸道动力学的物理特性，以及 将这些测量扩展到麻醉犬，利用逆行 导管技术；b)将观察到的呼吸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)和 连续流射流在气道内的位置，以最大限度减少 大叶非均质性；c)区分是否为不完全气相 弥散或V/Q变异增加是动脉低氧血症的原因 利用多重惰性气体技术应用于全肺和 CFV期间肺下叶过度充气；d)评估较新的组合 CFV与小潮气量漂移的CMV最优优化 两种机械通风方式的优点。在第二个系列中 我们打算将CFV作为一种实验工具来探索动物 呼吸衰竭的模型。治疗犬肺水肿：a)我们将使用 肺压力-容量关系的滞后性寻求最优 分流最小化时的肺泡压力(Palv)；b)在Palv恒定时， 我们将把肺容量和分流的变化联系起来，以推测其机制。 肺泡间质和肺泡腔间的水肿再分布； 将这些结果与CMV进行比较，将评估循环的作用 通风对水肿的分布和蓄积的影响。在犬类模型中 和猪气流阻塞，我们将测量影响 巨噬细胞减压术中多次惰性气体交换时的支气管痉挛和气体捕获 CFV，并测试CFV将气体捕获降至最低的效果。一份长期合同 这些研究的目的是加深对以下问题的了解 肺泡压力、肺体积、肺气量之间的相互关系 交流，以及煽动性疾病(水肿或支气管痉挛)。被阐明的 机制建议对替代模式的几个拟议扩展 根据正在模拟的临床条件进行通风。

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.