Hartford C G, van Schalkwyk J M, Rogers G G, Turner M J
Department of Physiology, University of the Witwatersrand Medical School and Johannesburg Hospital, South Africa.
Anesthesiology. 2000 Feb;92(2):550-8. doi: 10.1097/00000542-200002000-00039.
Dynamic intraesophageal pressure (Pes) is used to estimate intrapleural pressure (Ppl) to calculate lung compliance and resistance. This study investigated the nonhuman primate Ppl-Pes tissue barrier frequency response and the dynamic response requirements of Pes manometers.
In healthy monkeys and monkeys with acute lung injury undergoing ventilation, simultaneous Ppl and Pes were measured directly to determine the Ppl-Pes tissue barrier amplitude frequency response, using the swept-sine wave technique. The bandwidths of physiologic Pes waveforms acquired during conventional mechanical ventilation were calculated using digital low-pass signal filtering.
The Ppl-Pes tissue barrier is amplitude-uniform within the bandwidth of conventional Pes waveforms in healthy and acute lung injury lungs, and does not significantly attenuate Ppl-Pes signal transmission between 1 and 40 Hz. At Pes frequencies higher than conventional clinical regions of interest the Ppl-Pes barrier resonates significantly, is pressure amplitude dependent at low-pressure offsets, and is significantly altered by acute lung injury. Allowing for 5% or less Pes waveform error, the maximum Pes bandwidths during conventional ventilation were 1.9 Hz and 3.4 Hz for physiologic and extreme-case waveforms in healthy lungs and 4.6 Hz and 8.5 Hz during acute lung injury.
In monkeys, the Ppl-Pes tissue barrier has a frequency response suitable for Ppl estimation during low-frequency mechanical ventilation, and Pes manometers should have a minimum uniform frequency response up to 8.5 Hz. However, the Ppl-Pes tissue barrier adversely affects the accurate estimation of dynamic Ppl at high frequencies, with varied airway pressure amplitudes and offsets, such as the Ppl encountered during high-frequency oscillatory ventilation.
动态食管内压力（Pes）用于估计胸腔内压力（Ppl），以计算肺顺应性和阻力。本研究调查了非人灵长类动物Ppl - Pes组织屏障的频率响应以及Pes压力计的动态响应要求。
在健康猴子和接受通气的急性肺损伤猴子中，使用扫频正弦波技术直接同时测量Ppl和Pes，以确定Ppl - Pes组织屏障的幅度频率响应。使用数字低通信号滤波计算在传统机械通气期间获取的生理Pes波形的带宽。
在健康和急性肺损伤肺中，Ppl - Pes组织屏障在传统Pes波形的带宽内幅度均匀，并且在1至40 Hz之间不会显著衰减Ppl - Pes信号传输。在高于传统临床感兴趣区域的Pes频率下，Ppl - Pes屏障会发生显著共振，在低压偏移时与压力幅度相关，并且会因急性肺损伤而显著改变。允许Pes波形误差为5%或更小，在传统通气期间，健康肺中生理和极端情况波形的最大Pes带宽分别为1.9 Hz和3.4 Hz，急性肺损伤期间为4.6 Hz和8.5 Hz。
在猴子中，Ppl - Pes组织屏障具有适合在低频机械通气期间估计Ppl的频率响应，并且Pes压力计应具有至少高达8.5 Hz的均匀频率响应。然而，Ppl - Pes组织屏障会对高频下动态Ppl的准确估计产生不利影响，例如在高频振荡通气期间遇到的具有不同气道压力幅度和偏移的Ppl。
