Department of Anesthesiology, Section for Surgical Intensive Care, Kantonsspital Luzern, Spitalstrasse, Luzern, Switzerland.
Crit Care. 2009;13(1):R4. doi: 10.1186/cc7693. Epub 2009 Jan 23.
The effect of expiratory endotracheal tube (ETT) resistance on dynamic lung inflation is unknown. We hypothesized that ETT resistance causes dynamic lung hyperinflation by impeding lung emptying. We further hypothesized that compensation for expiratory ETT resistance by automatic tube compensation (ATC) attenuates dynamic lung hyperinflation.
A ventilator equipped with the original ATC mode and operating in a pressure-targeted mode was connected to a physical lung model that consists of four equally sized glass bottles filled with copper wool. Inspiratory pressure, peak expiratory flow, trapped lung volume and intrinsic positive end-expiratory pressure (PEEP) were assessed at combinations of four inner ETT diameters (7.0, 7.5, 8.0 and 8.5 mm), four respiratory rates (15, 20, 25 and 30/minute), three inspiratory pressures (3.0, 4.5 and 6.0 cmH2O) and four lung compliances (113, 86, 58 and 28 ml/cmH2O). Intrinsic PEEP was measured at the end of an expiratory hold manoeuvre.
At a given test lung compliance, inspiratory pressure and ETT size, increasing respiratory rates from 15 to 30/minutes had the following effects: inspiratory tidal volume and peak expiratory flow were decreased by means of 25% (range 0% to 51%) and 11% (8% to 12%), respectively; and trapped lung volume and intrinsic PEEP were increased by means of 25% (0% to 51%) and 26% (5% to 45%), respectively (all P < 0.025). At otherwise identical baseline conditions, introduction of expiratory ATC significantly attenuated (P < 0.025), by approximately 50%, the respiratory rate-dependent decreases in inspiratory tidal volume and the increases in trapped lung volume and intrinsic PEEP.
In a lung model of pressure-targeted ventilation, expiratory ETT resistance caused dynamic lung hyperinflation during increases in respiratory rates, thereby reducing inspiratory tidal volume. Expiratory ATC attenuated these adverse effects.
呼气气管内导管（ETT）阻力对动态肺充气的影响尚不清楚。我们假设 ETT 阻力通过阻碍肺排空导致动态肺过度充气。我们进一步假设自动管补偿（ATC）补偿呼气 ETT 阻力会减轻动态肺过度充气。
配备原始 ATC 模式的呼吸机连接到由四个装满铜毛的等大小玻璃瓶组成的物理肺模型。在四个内 ETT 直径（7.0、7.5、8.0 和 8.5 毫米）、四个呼吸频率（15、20、25 和 30 次/分钟）、三个吸气压力（3.0、4.5 和 6.0 cmH2O）和四个肺顺应性（113、86、58 和 28 ml/cmH2O）的组合下评估吸气压力、呼气峰流量、被困肺容积和内在呼气末正压（PEEP）。在呼气保持操作结束时测量内在 PEEP。
在给定的测试肺顺应性、吸气压力和 ETT 大小下，将呼吸频率从 15 次/分钟增加到 30 次/分钟会产生以下影响：吸气潮气量和呼气峰流量分别减少 25%（0%至 51%）和 11%（8%至 12%）；被困肺容积和内在 PEEP 分别增加 25%（0%至 51%）和 26%（5%至 45%）（均 P <0.025）。在其他相同的基线条件下，引入呼气 ATC 显著减轻（P <0.025），大约 50%，与呼吸频率相关的吸气潮气量降低和被困肺容积和内在 PEEP 增加。
在压力目标通气的肺模型中，呼气 ETT 阻力在呼吸频率增加时导致动态肺过度充气，从而降低吸气潮气量。呼气 ATC 减轻了这些不利影响。
