Objectives

To compare pulmonary gas exchange, tissue oxygenation and cardiovascular effects of four levels of end-expiratory pressure: no positive end-expiratory pressure (ZEEP), positive end-expiratory pressure (PEEP) of maximal respiratory system compliance (PEEPmaxC_rs), PEEPmaxC_rs + 2 cmH₂O (PEEPmaxC_rs+2), PEEPmaxC_rs + 4 cmH₂O (PEEPmaxC_rs+4), in isoflurane-anesthetized dogs.

Study design

Prospective randomized crossover study.

Animals

A total of seven healthy male Beagle dogs, aged 1 year and weighing 10.2 ± 0.7 kg (mean ± standard deviation).

Methods

The dogs were administered acepromazine and anesthesia was induced with propofol and maintained with isoflurane. Ventilation was controlled for 4 hours with ZEEP, PEEPmaxC_rs, PEEPmaxC_rs+2 or PEEPmaxC_rs+4. Cardiovascular, pulmonary gas exchange and tissue oxygenation data were evaluated at 5, 60, 120, 180 and 240 minutes of ventilation and compared using a mixed-model anova followed by Bonferroni test. p < 0.05 was considered significant.

Results

Cardiac index (CI) and mean arterial pressure (MAP) were lower in all PEEP treatments at 5 minutes when compared with ZEEP. CI persisted lower throughout the 4 hours only in PEEPmaxC_rs+4 with the lowest CI at 5 minutes (2.15 ± 0.70 versus 3.45 ± 0.94 L minute^–1 m^–2). At 180 and 240 minutes, MAP was lower in PEEPmaxC_rs+4 than in PEEPmaxC_rs, with the lowest value at 180 minutes (58 ± 7 versus 67 ± 7 mmHg). Oxygen delivery index (DO₂I) was lower in PEEPmaxC_rs+4 than in ZEEP at 5, 60, 120 and 180 minutes. Venous admixture was not different among treatments.

Conclusion and clinical relevance

The use of PEEP caused a transient decrease in MAP and CI in lung-healthy dogs anesthetized with isoflurane, which improved after 60 minutes of ventilation in all levels of PEEP except PEEPmaxC_rs+4. A clinically significant improvement in arterial oxygenation and DO₂I was not observed with PEEPmaxC_rs and PEEPmaxC_rs+2 in comparison with ZEEP, whereas PEEPmaxC_rs+4 decreased DO₂I.

中文翻译：

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具有四个呼气末正压水平的异氟醚麻醉、机械通气比格犬的心血管功能、肺气体交换和组织氧合

目标

比较四种呼气末压力水平的肺气体交换、组织氧合和心血管影响：无呼气末正压 (ZEEP)、最大呼吸系统顺应性的呼气末正压 (PEEP) (PEEPmax C _rs )、PEEPmax C _rs  + 2 cmH ₂ O (PEEPmax C _rs+2 )、PEEPmax C _rs  + 4 cmH ₂ O (PEEPmax C _rs+4 )，在异氟醚麻醉的狗中。

学习规划

前瞻性随机交叉研究。

动物

共有 7 只健康的雄性 Beagle 犬，年龄 1 岁，体重 10.2 ± 0.7 kg（平均值 ± 标准差）。

方法

给狗服用乙酰丙嗪，用丙泊酚诱导麻醉，用异氟醚维持麻醉。用 ZEEP、PEEPmax C _rs、PEEPmax C _rs+2或 PEEPmax C _rs+4控制通气 4 小时。在通气5、60、120、180和 240 分钟时评估心血管、肺气体交换和组织氧合数据，并使用混合模型方差分析和 Bonferroni 测试进行比较。p < 0.05 被认为是显着的。

结果

与 ZEEP 相比，所有 PEEP 治疗 5 分钟时的心脏指数 (CI) 和平均动脉压 (MAP) 均较低。仅在 PEEPmax C _rs+4中 CI 在 4 小时内持续较低，在 5 分钟时 CI 最低（2.15 ± 0.70对3.45 ± 0.94 L·min ^–1 m ^–2）。在 180 分钟和 240 分钟时，PEEPmax C _rs+4的 MAP 低于PEEPmax C _rs，最低值在 180 分钟（58 ± 7对67 ± 7 mmHg）。在 5、60、120 和 180 分钟时， PEEPmax C _rs+4的氧气输送指数 (DO ₂ I) 低于 ZEEP 。静脉混合物在治疗之间没有差异。

结论和临床相关性

在用异氟醚麻醉的肺健康犬中，使用 PEEP 会导致 MAP 和 CI 短暂降低，通气 60 分钟后，除 PEEPmax C _rs+4外，所有 PEEP 水平的通气 60 分钟后均有所改善。与 ZEEP 相比，PEEPmax C _rs和 PEEPmax C _rs+2未观察到动脉氧合和 DO ₂ I 的临床显着改善，而 PEEPmax C _rs+4降低了 DO ₂ I。