Objective

To evaluate the influence of reservoir bag types, volumes and previous use on the peak pressures (Pmax) and the times to develop 30 cmH₂O pressure (P30) within a nonrebreathing system with a closed adjustable pressure-limiting (APL) valve.

Study design

In vitro study using three-way factorial design with repeated measure on one factor.

Subjects

A total of 75 new anesthesia reservoir bags (five types, three volumes, five bags from each type × volume). The bag types were reusable latex (RL), disposable latex (DL) and three disposable neoprene (DN-1, DN-2 and DN-3).

Methods

Each bag was tested three times (treatments): new, after prestretching and 1 week later. The bags were attached to a Bain system and anesthesia machine with closed APL valve and patient port with O₂ flow 2 L minute^–1 until Pmax was reached. The Pmax and time to reach P30 values were determined from recorded pressure traces. General linear mixed model analysis was used to examine the effects of bag type, volume and treatment. One-sided 95% upper prediction limits of Pmax were calculated to test the null hypothesis that predicted Pmax of new bags would be ≥ 50 cmH₂O for each factor combination.

Results

RL bags were the least and DN-3 bags were the most compliant. Prestretching increased compliance in all bag types. Smaller bags of RL, DL and DN-1 were less compliant than larger ones. The predicted Pmax values were < 50 cmH₂O only for DN-3 bags after prestretching. The time to reach P30 was critically low when using 0.5 L bags (median 17 seconds).

Conclusions and clinical relevance

To minimize the risk of barotrauma, highly compliant reservoir bags (e.g. DN-3) are recommended and reusable bags should be avoided. Bags should be prestretched before first use, 0.5 L bags should be avoided and fresh gas flow minimized.

中文翻译：

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作为非再呼吸系统中气道压力限制装置的储液袋的量化

客观的

评估储液袋类型、容量和先前使用对峰值压力 (Pmax) 的影响以及在具有关闭的可调限压 (APL) 阀的非重复呼吸系统中产生 30 cmH ₂ O 压力 (P30) 的时间。

学习规划

使用三因素析因设计对一个因素进行重复测量的体外研究。

科目

新增麻醉储液袋共75个（五款三卷，每款五袋×体积）。袋子类型是可重复使用的乳胶（RL）、一次性乳胶（DL）和三种一次性氯丁橡胶（DN-1、DN-2 和 DN-3）。

方法

每个袋子都测试了 3 次（处理）：新的、预拉伸后和 1 周后。将袋子连接到贝恩系统和麻醉机上，该麻醉机具有关闭的 APL 阀和患者端口，O ₂流量为 2 L min ^–1，直到达到 Pmax。Pmax 和达到 P30 值的时间由记录的压力轨迹确定。使用一般线性混合模型分析来检查袋子类型、体积和处理的影响。计算了 Pmax 的单边 95% 预测上限以检验每个因素组合的新袋子的预测 Pmax ≥ 50 cmH ₂ O的无效假设。

结果

RL 袋子的合规性最低，DN-3 袋子的合规性最高。预拉伸增加了所有袋子类型的顺应性。较小的 RL、DL 和 DN-1 袋比大袋的合规性较差。仅对于预拉伸后的 DN-3 袋子，预测的 Pmax 值 < 50 cmH ₂ O。使用 0.5 L 袋子时，达到 P30 的时间非常短（中位数为 17 秒）。

结论和临床相关性

为尽量减少气压伤的风险，建议使用高度顺应性的储液袋（例如 DN-3），并应避免使用可重复使用的储液袋。首次使用前应预拉伸袋子，应避免使用 0.5 L 袋子，并尽量减少新鲜气体流量。