Gowski D T, Delgado E, Miro A M, Tasota F J, Hoffman L A, Pinsky M R
Department of Anesthesiology, School of Medicine, University of Pittsburgh, USA.
Crit Care Med. 1997 Jan;25(1):145-52. doi: 10.1097/00003246-199701000-00027.
Pressure-control ventilation minimizes alveolar overdistention by limiting peak airway pressure, but a consequence of this pressure limitation may be a reduction in tidal volume with subsequent hypercarbia. Tracheal gas insufflation (TGI) can be used in combination with pressure-control ventilation to augment CO2 elimination. During pressure-control ventilation with continuous TGI, we observed that peak airway pressure increased above the set inspiratory pressure. Based on this observation, we investigated the ability of the pressure-control ventilator circuit to compensate for continuous TGI and the effect of insertion of a pressure relief valve to eliminate over-pressurization.
University research laboratory.
Using an artificial lung model, we studied the effects of continuous TGI with varying catheter flows (0, 2, 6, and 10 L/ min); ventilator frequencies (10 and 20 breaths/min); inspiratory duty cycles (0.33, 0.50, and 0.67); lung compliance (0.01, 0.02, and 0.04 L/cm H2O); and airway resistance (5, 20, and 50 cm H2O/L/sec) on: a) peak airway pressure; b) total inspiratory tidal volume; c) ventilator-derived tidal volume; and d) intrapulmonary pressure at end-exhalation (auto-PEEP). Tests were performed with and without a pressure relief valve whose threshold "pop-off" pressure was adjusted to match the set inspiratory pressure (35 cm H2O) for a total of 432 experimental conditions.
Our data demonstrate that pressure-control ventilation augmented with continuous TGI can increase peak airway pressure above set inspiratory pressure due to delivery of a higher than intended tidal volume. Predisposing conditions include catheter flow rates of 6 and 10 L/min, long inspiratory time, low compliance, and low resistance. With the pressure relief valve, peak airway pressure was maintained at the set inspiratory pressure and total inspiratory tidal volume remained constant.
A pressure relief valve is a necessary adjunct to maintain peak airway pressure at set inspiratory pressure and keep total inspiratory tidal volume constant when continuous TGI is administered in conjunction with pressure-control ventilation.
压力控制通气通过限制气道峰值压力使肺泡过度扩张最小化，但这种压力限制的一个后果可能是潮气量减少并随后出现高碳酸血症。气管内气体吹入（TGI）可与压力控制通气联合使用以增强二氧化碳清除。在持续TGI的压力控制通气期间，我们观察到气道峰值压力升高超过设定的吸气压力。基于这一观察结果，我们研究了压力控制通气回路补偿持续TGI的能力以及插入压力释放阀以消除过压的效果。
大学研究实验室。
使用人工肺模型，我们研究了不同导管流量（0、2、6和10升/分钟）、通气频率（10和20次/分钟）、吸气占空比（0.33、0.50和0.67）、肺顺应性（0.01、0.02和0.04升/厘米水柱）以及气道阻力（5、20和50厘米水柱/升/秒）的持续TGI对以下方面的影响：a）气道峰值压力；b）总吸气潮气量；c）呼吸机衍生潮气量；d）呼气末肺内压（内源性呼气末正压）。在有和没有压力释放阀的情况下进行测试，压力释放阀的阈值“起跳”压力调整为与设定的吸气压力（35厘米水柱）相匹配，总共432种实验条件。
我们的数据表明，由于输送的潮气量高于预期，持续TGI增强的压力控制通气可使气道峰值压力升高超过设定的吸气压力。诱发条件包括导管流速为6和10升/分钟、吸气时间长、顺应性低和阻力低。使用压力释放阀时，气道峰值压力维持在设定的吸气压力，总吸气潮气量保持恒定。
当持续TGI与压力控制通气联合使用时，压力释放阀是将气道峰值压力维持在设定吸气压力并使总吸气潮气量保持恒定的必要辅助装置。
