Moens Y, Lagerweij E, Gootjes P, Poortman J
Department of Anaesthesia, Faculty of Veterinary Medicine, University of Utrecht, The Netherlands.
Am J Vet Res. 1998 Mar;59(3):307-12.
To study effects of intermittent positive-pressure ventilation (IPPV) with large tidal volumes and addition of positive end-expiratory pressure (PEEP) on maldistribution of ventilation in anesthetized horses positioned in lateral recumbency.
6 healthy adult horses.
Anesthesia was induced by i.v. infusion of thiopental sodium and guiafenesin and was maintained with supplemental doses of thiopental and i.v. infusion of chloral hydrate. Functional separation of the lungs was achieved, using a tube-in-tube intubation technique. Intermittent positive-pressure ventilation of both lungs with air was done by use of an anesthetic circle system and a ventilator. Data were collected during spontaneous respiration and during IPPV, using increasing tidal volumes with and without PEEP of 10 and 20 cm of H2O.
Uneven distribution of inspired gas between the lungs that existed during spontaneous respiration was not altered by IPPV and large tidal volumes. Addition of PEEP caused a significant and reversible shift of inspired gas to the dependent lung and preferentially increased functional residual capacity of the nondependent lung. This was accompanied by significant increase in PaO2. With IPPV, the combined effects of PEEP and large tidal volume caused an increase of the fractional distribution of inspired gas to the dependent lung from 34% to 50%, accompanied by an increase in PaO2 and alveolar dead space of both lungs.
Use of PEEP during IPPV changes distribution of inspired gas. Increased in PaO2 can be attributed to improved ventilation-perfusion, especially in the dependent lung, in which previously collapsed lung units might have been reopened and participated again in gas exchange after redistribution of inspired gas. The most pronounced effects of IPPV and PEEP were associated with high airway pressures, which are likely to offset the beneficial effects of the increase of PaO2 on total oxygen availability to the tissues because of the expected negative effects on cardiac output.
研究大潮气量间歇正压通气（IPPV）及加用呼气末正压（PEEP）对侧卧麻醉马通气分布不均的影响。
6匹健康成年马。
静脉输注硫喷妥钠和愈创木酚甘油醚诱导麻醉，并用补充剂量的硫喷妥钠和静脉输注水合氯醛维持麻醉。采用双腔气管插管技术实现肺功能分离。使用麻醉环路系统和呼吸机对双肺进行空气间歇正压通气。在自主呼吸和IPPV期间收集数据，采用递增潮气量，分别设置有和无10 cmH₂O及20 cmH₂O的PEEP。
自主呼吸时存在的双肺间吸入气体分布不均未因IPPV和大潮气量而改变。加用PEEP导致吸入气体显著且可逆地向低位肺转移，并优先增加了高位肺的功能残气量。这伴随着动脉血氧分压（PaO₂）显著升高。在IPPV时，PEEP和大潮气量的联合作用使吸入气体向低位肺转移的比例从34%增加至50%，同时双肺的PaO₂和肺泡无效腔均增加。
IPPV期间使用PEEP可改变吸入气体分布。PaO₂升高可归因于通气-灌注改善，尤其是在低位肺，先前萎陷的肺单位可能重新开放并在吸入气体重新分布后再次参与气体交换。IPPV和PEEP最显著的效应与高气道压有关，由于对心输出量预期的负面影响，这可能抵消PaO₂升高对组织总氧供的有益作用。
