Background

During spontaneous breathing trial, low-pressure support is thought to compensate for endotracheal tube resistance, but it actually should provide overassistance. Automatic tube compensation is an option available in the ventilator to compensate for flow-resistance of endotracheal tube. Its effects on patient effort have been poorly investigated. We aimed to compare the effects of low-pressure support and automatic tube compensation during spontaneous breathing trial on breathing power and lung ventilation distribution.

Results

We performed a randomized crossover study in 20 patients ready to wean. Each patient received both methods for 30 min separated by baseline ventilation: pressure support 0 cmH₂O and automatic tube compensation 100% in one period and pressure support 7 cmH₂O without automatic tube compensation in the other period, a 4 cmH₂O positive end-expiratory pressure being applied in each. Same ventilator brand (Evita XL, Draeger, Germany) was used. Breathing power was assessed from Campbell diagram with esophageal pressure, airway pressure, flow and volume recorded by a data logger. Lung ventilation distribution was assessed by using electrical impedance tomography (Pulmovista, Draeger, Germany). During the last 2 min of low-pressure support and automatic compensation period breathing power and lung ventilation distribution were measured on each breath. Breathing power generated by the patient’s respiratory muscles was 7.2 (4.4–9.6) and 9.7 (5.7–21.9) J/min in low-pressure support and automatic tube compensation periods, respectively (P = 0.011). Lung ventilation distribution was not different between the two methods.

Conclusions

We found that ATC was associated with higher breathing power than low PS during SBT without altering the distribution of lung ventilation.

中文翻译：

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断奶自发呼吸试验中的低压支持与自动管补偿。

背景

在自发呼吸试验中，低压支持被认为可以补偿气管插管阻力，但实际上应该提供过度辅助。呼吸机中提供了自动管道补偿选项，以补偿气管导管的流阻。其对患者努力的影响尚未得到很好的研究。我们旨在比较自发性呼吸试验中低压支持和自动管补偿对呼吸功率和肺通气分布的影响。

结果

我们对准备断奶的20例患者进行了一项随机交叉研究。每位患者均接受两种方法进行30分钟的基线通气分隔：一个时期内压力支持0 cmH ₂ O和自动导管补偿100％，另一时期内不进行自动导管补偿的压力支持7 cmH ₂ O，另一时期为4 cmH ₂在每个呼吸机上都施加一个正的呼气末压。使用相同的呼吸机品牌（Evita XL，德国德拉格）。根据坎贝尔图，通过数据记录仪记录的食管压力，气道压力，流量和体积评估呼吸功率。肺通气分布通过电阻抗断层扫描（Pulmovista，德拉格，德国）进行评估。在低压支持和自动补偿期间的最后2分钟内，对每次呼吸测量呼吸功率和肺通气量分布。在低压支撑和自动管补偿期间，患者呼吸肌产生的呼吸力分别为7.2（4.4–9.6）和9.7（5.7–21.9）J / min（P  = 0.011）。两种方法之间的肺通气分布无差异。

结论

我们发现，在SBT期间，ATC与低PS相比具有更高的呼吸能力，而不会改变肺通气的分布。