PULMONARY CAPILLARY PRESSURE IN DOGS AND HUMANS

肺循环是一个高电容系统，可以适应 血容量变化五倍，而压力变化很小。 在肺毛细血管维持恒定的滤过压 对于避免会阻碍空气的肺水肿很重要 交换。直到最近，人们还认为肺毛细血管 压力Ppc)可用Gaar方程近似为Ppc=Pl.4 (PPA-Pla)。在临床上，PPC通常被认为等于肺 动脉闭塞或楔压PPW)。然而，这些近似值 在许多临床病例中并不能准确预测PPC 条件。 这些研究的目的是评估准确性、重复性 三种估测肺毛细血管技术的局限性 压力(PPC)：目测方法，计算机定义 肺动脉压力曲线中的断点时间，以及 由计算机模拟得出的理论购买力平价。这些方法将是 在病人、狗和双胞胎中进行相互比较 在开胸犬肺中闭塞PPC。肺的划分 血管阻力(PVR)进入前(Ra)和后(Rv)毛细血管 组件和PPC与楔形压力的比较将是 在改变的生理条件下进行评估。其中包括：急性 主动脉阻断术中主动脉阻断引起的血容量变化 重建、慢性心力衰竭伴血管外 红细胞增多症后的容量保留、粘度变化和 机械通气时所见的气道压力和正压 呼气末压力，油酸损伤，毛细血管增加 通透性，增加血管阻力(缺氧)和 电容和电阻可以任意改变，其结果是 PPC已确定。然后，可以将测量的PPC与预测的PPC进行比较 理论价值。 在狗的肺中，将使用标准的实验方案。在病人身上， 分析肺动脉压力示踪不需要额外的 生理上的侵入。

The pulmonary circulation is a high capacitance system that can adapt to a five fold variation in blood volume with little change in pressure. Maintaining a constant filtration pressure at the pulmonary capillaries is important in avoiding pulmonary edema which would impede air exchange. Until recently, it was assumed that pulmonary capillary pressure Ppc) could be approximated by the Gaar equation as Ppc=Pla + .4 (Ppa-Pla). Clinically Ppc is often assumed to be equal to the pulmonary arterial occlusion or wedge pressure Ppw). However, these approximations are not an accurate prediction of Ppc in a number of clinical conditions. The goal of these studies is to evaluate the accuracy, reproducibility and limitations of three techniques to estimate pulmonary capillary pressure (Ppc): the visual determination method, computer definition of the break point time in the pulmonary arterial pressure profile, and theoretical Ppc derived from computer simulation. These methods will be compared to one another in patients and in dogs and to the double occlusion PpC in open-chested dog lungs. The division of pulmonary vascular resistance (PVR) into pre (ra) and post (rv) capillary components and the Ppc as compared to the wedge pressure will be evaluated under altered physiological conditions. These include: acute changes in blood volume induced by aortic cross clamping during aortic reconstruction, chronic heart failure with extravascular volumeretention, viscosity changes after polycythemia, and alteration in airway pressure such as seen during mechanical ventilation and positive end expiratory pressure, oleic acid injury, increasing capillary permeability, and increasing vascular resistance (hypoxia) and capacitance and resistance can be arbitrarily changed and the resultant Ppc determined. The measured Ppc can then be compared to predicted theoretical values. In dog lungs standard experimental protocols will be used. In patients, analysis of the pulmonary artery pressure tracing requires no additional physiological trespass.