Morris Kevin, Cox Peter, Frndova Helena, Holowka Stephanie, Babyn Paul
Department of Critical Care Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada.
Pediatr Pulmonol. 2007 Mar;42(3):204-9. doi: 10.1002/ppul.20522.
To study the effect of a sustained inflation (SI) maneuver on the regional distribution of gas and perfluorocarbon (PFC) during partial liquid ventilation (PLV) in normal pigs using computerized densitometry.
Observational study.
Animal research laboratory.
Three healthy anaesthetized pigs.
Partial liquid ventilation, lung recruitment, CT densitometry.
Lungs were filled with PFC to "liquid functional residual capacity (FRC)" (35-41 ml/kg) and CT images were recorded at a series of predetermined airway pressure levels (0, 20, 30, 40 cm H2O) both before and after SI to an airway pressure of 40 cm H2O for 30 sec. Anterior, middle, and posterior regions from upper (apical lung) to lower (basal lung) CT slices were analyzed at each pressure level for Hounsfield units to describe the relative distribution of gas and PFC before and after SI. Using an occlusion technique true gas volume above FRC was determined at each pressure level, before and after SI, and a pressure-volume (gas) envelope determined for each animal.
At low airway pressures (<20 cm H2O) gas was distributed predominantly to the anterior (non-dependent) part of the lung and PFC predominantly to the posterior (dependent) lung. Gas and liquid were more uniformly distributed throughout the lung at airway pressures >20 cm H2O. Generation of a pressure-volume (gas) envelope for each animal demonstrated an increase in total gas volume above FRC at each pressure level following recruitment of the lung with SI. However, marked regional differences were evident with the greatest effects of SI seen at higher airway pressures in posterior and basal regions.
The healthy PFC filled lung demonstrates an increase in total gas volume following SI. CT densitometry suggests marked heterogeneity of gas/PFC distribution between different regions of lung and heterogeneity of response to SI.
采用计算机密度测定法研究持续充气（SI）操作对正常猪部分液体通气（PLV）期间气体和全氟化碳（PFC）区域分布的影响。
观察性研究。
动物研究实验室。
三只健康的麻醉猪。
部分液体通气、肺复张、CT密度测定。
将肺填充至“液体功能残气量（FRC）”（35 - 41 ml/kg）的PFC，在SI至气道压力40 cm H2O持续30秒前后，于一系列预定气道压力水平（0、20、30、40 cm H2O）记录CT图像。在每个压力水平分析从上（肺尖）到下（肺底）CT切片的前、中、后区域的亨氏单位，以描述SI前后气体和PFC的相对分布。使用阻断技术在SI前后的每个压力水平确定高于FRC的真实气体体积，并为每只动物确定压力 - 体积（气体）曲线。
在低气道压力（<20 cm H2O）时，气体主要分布于肺的前部（非下垂部），PFC主要分布于后部（下垂部）肺。在气道压力>20 cm H2O时，气体和液体在整个肺中分布更均匀。为每只动物生成压力 - 体积（气体）曲线显示，在通过SI使肺复张后，每个压力水平高于FRC的总气体体积增加。然而，明显的区域差异很明显，在较高气道压力下，后部和基底区域对SI的影响最大。
健康的填充PFC的肺在SI后总气体体积增加。CT密度测定表明肺不同区域之间气体/PFC分布存在明显异质性以及对SI反应的异质性。
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