导管阻力补偿与压力支持通气对机械通气患者自主呼吸试验的影响

Comparison of respiratory mechanics during spontaneous breathing trial between automatic tube compensation and pressure support ventilation

目的 观察导管阻力补偿技术（ATC）与压力支持通气（PSV）对接受机械通气支持的呼吸衰竭患者在自主呼吸试验（SBT）时通气参数的影响。方法 呼吸衰竭患者26例，均为接受气管插管及机械通气支持24h以上者，在治疗过程中病情稳定准备进行撤机试验。SBT时预置呼气末气道正压（PEEP）为75％～80％的内源性PEEP（PEEPi），启动ATC时根据气管插管直径将补偿比例分别设置为40％、80％和100％，应用PSV时的吸气压力支持（PS）水平分别设置为4，6，8和10cmH20。结果 患者在ATC补偿比例为40％和80％时的各通气参数无明显变化，当补偿比例达到100％时，潮气量（VT）明显增高[（480.0±62．7）mL]，而呼吸频率（RR）、吸气时间比（TI／Tlot）和浅快呼吸指数（RSBI）则显著降低（P均〈0．05）。PSV时随着PS水平的增高，VT逐渐增高，PS为10cmH2O时的VT与PS为4～6cmH20时相比存在显著差异（P〈0．05）；而此时的RR则降至（14．6±3．7）次／min。不同PS水平时的分钟通气量（MV）及吸气峰流速（PIFR）均无明显差异。PS为10cmH20时的RSBI最小，仅为（38．2±8．5）次·min^-1·L^-1。PS为8cmH2O时的RR、RSBI和TI／Tlot与ATC为100％时相近（P〉0．05）。当IX3≥6cmH2O时，患者的平均气道压（MAP）明显高于ATC时。结论 ATC技术与PSV一样通过提供一定的预置压力，以帮助患者克服人工气道所引起的阻力。当ATC补偿比例为100％时，患者的自主通气状况与较高水平PSV（8～10cmH2O）通气时相似，呼吸作功也相近，但气道压力却明显降低。应用ATC时患者的自主呼吸接近正常状态，有利于临床医师评价其SBT的结果。

Objective To investigate the effects of automatic tube compensation （ATC） and pressure support ventilation （PSV） during spontaneous breathing trial （SBT） used for mechanical ventilation weaning. Methods 26 patients （mean age 65 ± 7 years old） with acute respiratory failure after mechanical ventilation for at least 24 hours who were stable and ready for weaning were enrolled. All patients were intubated with tube diameter 7.5-8.0 nun, underwent a 30 min SBT with different level of ATC （40%, 80% and 100% ）, or PSV （4, 6, 8 and 10 cm H2O）. Positive end-expiratory pressure （PEEP） was set about 75%-80% of intrinsic PEEP （ PEEPi）. Results During ATC （ 100% ） breathing, tidal volume （VT） was higher than ATC （40%） and ATC （80%） breathing, whereas respiratory rate （RR）, duty cycle （TI/Tlot） and rapid shallow breathing index （RSBI） were much lower. When PS level increased to 10 cm H2O, patients＇ Vwwas also increased, but RR and RSBI were decreased to （ 14.6±.7） breaths/min and （38.2 ± 8.5） breaths·min^-1 · L^-1, respectively. No differences were found in minute ventilation （MV） and peak inspimtory flow rate （PIFR） at different PS levels. RR, RSBI and TI/Tlot during ATC （100%） breathing were not significant different from those at PSV of 8 cm H2O. As PS level≥6 cm H2O, the mean airway pressure （MAP） was markedly increased than that during ATC breathing. Conclusions In weaning from mechanical ventilation, patients＇ workload during SBT is reduced by ATC at a compensation level of 100%, which is equivalent to PSV of 8-10 em HzO, however, the airway pressure （Paw） was somewhat lower.