Greenough A, Dimitriou G, Prendergast M, Milner A D
King's College School of Medicine and Dentistry, Dept of Child Health, Bessemer Road, London, UK SE5 9PJ.
Cochrane Database Syst Rev. 2008 Jan 23(1):CD000456. doi: 10.1002/14651858.CD000456.pub3.
During synchronized mechanical ventilation, positive airway pressure and spontaneous inspiration coincide. If synchronous ventilation is provoked, adequate gas exchange should be achieved at lower peak airway pressures, potentially reducing baro/volutrauma, air leak and bronchopulmonary dysplasia. Synchronous ventilation can potentially be achieved by manipulation of rate and inspiratory time during conventional ventilation and employment of patient triggered ventilation.
To compare the efficacy of: (i) synchronized mechanical ventilation, delivered as high frequency positive pressure ventilation (HFPPV) or patient triggered ventilation - assist control ventilation (ACV) or synchronous intermittent mandatory ventilation (SIMV)) with conventional ventilation (CMV) (ii) different types of triggered ventilation (ACV, SIMV, pressure regulated volume control ventilation (PRVCV) and SIMV plus pressure support (PS) SEARCH STRATEGY: Searches from 1985-2007 of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2007),Oxford Database of Perinatal Trials, MEDLINE, previous reviews, abstracts and symposia proceedings; hand searches of journals in the English language and contact with expert informants.
Randomised or quasi-randomised clinical trials comparing synchronized ventilation delivered as high frequency positive pressure ventilation (HFPPV) or triggered ventilation (ACV/SIMV) to conventional mechanical ventilation (CMV) in neonates. Randomised trials comparing different triggered ventilation modes (ACV, SIMV, SIMV plus PS and PRVCV) in neonates.
Data regarding clinical outcomes including mortality, air leaks (pneumothorax or pulmonary interstitial emphysema (PIE)), severe intraventricular haemorrhage (grades 3 and 4), bronchopulmonary dysplasia (BPD) (oxygen dependency beyond 28 days), moderate/severe BPD (oxygen/respiratory support dependency beyond 36 weeks postmenstrual age (PMA) and duration of weaning/ventilation. Four comparisons were made: (i) HFPPV vs. CMV; (ii) ACV/SIMV vs. CMV; (iii) ACV vs. SIMV or PRVCV vs. SIMV (iv) SIMV plus PS vs. SIMV. Data analysis was conducted using relative risk for categorical outcomes, weighted mean difference for outcomes measured on a continuous scale.
Fourteen studies were eligible for inclusion. The meta-analysis demonstrates that HFPPV compared to CMV was associated with a reduction in the risk of air leak (typical relative risk for pneumothorax was 0.69, 95% CI 0.51, 0.93). ACV/SIMV compared to CMV was associated with a shorter duration of ventilation (weighted mean difference -34.8 hours, 95% CI -62.1, -7.4). ACV compared to SIMV was associated with a trend to a shorter duration of weaning (weighted mean difference -42.4 hours, 95% CI -94.4, 9.6). Neither HFPPV nor triggered ventilation was associated with a significant reduction in the incidence of BPD. There was a non-significant trend towards a lower mortality rate using HFPPV vs. CMV and a non-significant trend towards a higher mortality rate using triggered ventilation vs. CMV. No disadvantage of HFPPV or triggered ventilation was noted regarding other outcomes. Since the last review, two new patient triggered modes have been included: pressure regulated volume control ventilation (PRVCV) and SIMV plus pressure support. Each of these methods of ventilation has only been tested in single randomised trials with no significant advantages in important outcomes.
AUTHORS' CONCLUSIONS: Compared to conventional ventilation, benefit is demonstrated for both HFPPV and triggered ventilation with regard to a reduction in air leak and a shorter duration of ventilation, respectively. In none of the trials was complex respiratory monitoring undertaken and thus it is not possible to conclude that the mechanism of producing those benefits is by provocation of synchronized ventilation. Further trials are needed to determine whether synchronized ventilation is associated with other benefits, but optimisation of trigger and ventilator design with respect to respiratory diagnosis is encouraged before embarking on further trials. It is essential newer forms of triggered ventilation are tested in adequately powered randomised trials with long-term outcomes before they are incorporated into routine clinical practice.
在同步机械通气过程中，气道正压与自主吸气同时发生。如果引发同步通气，在较低的气道峰压下应能实现充分的气体交换，这有可能减少气压伤/容积伤、气漏和支气管肺发育不良。在传统通气期间通过调整频率和吸气时间以及采用患者触发通气，有可能实现同步通气。
比较以下各项的疗效：(i) 作为高频正压通气（HFPPV）或患者触发通气 - 辅助控制通气（ACV）或同步间歇指令通气（SIMV）进行的同步机械通气与传统通气（CMV）；(ii) 不同类型的触发通气（ACV、SIMV、压力调节容量控制通气（PRVCV）和SIMV加压力支持（PS））。
检索1985 - 2007年考克兰系统评价数据库（CENTRAL，考克兰图书馆，2007年第2期）、牛津围产期试验数据库、MEDLINE、既往综述、摘要和研讨会论文集；手工检索英文期刊并与专家信息提供者联系。
将作为高频正压通气（HFPPV）或触发通气（ACV/SIMV）进行的同步通气与新生儿传统机械通气（CMV）进行比较的随机或半随机临床试验。比较新生儿不同触发通气模式（ACV、SIMV、SIMV加PS和PRVCV）的随机试验。
关于临床结局的数据，包括死亡率、气漏（气胸或肺间质气肿（PIE））、重度脑室内出血（3级和4级）、支气管肺发育不良（BPD）（28天以上的氧依赖）、中度/重度BPD（月经后年龄（PMA）36周后氧/呼吸支持依赖）以及撤机/通气时间。进行了四项比较：(i) HFPPV与CMV；(ii) ACV/SIMV与CMV；(iii) ACV与SIMV或PRVCV与SIMV；(iv) SIMV加PS与SIMV。使用分类结局的相对风险、连续量表测量结局的加权平均差进行数据分析。
14项研究符合纳入标准。荟萃分析表明，与CMV相比，HFPPV与气漏风险降低相关（气胸的典型相对风险为0.69，95%可信区间0.51，0.93）。与CMV相比，ACV/SIMV与通气时间缩短相关（加权平均差 -34.8小时，95%可信区间 -62.1， -7.4）。与SIMV相比，ACV与撤机时间缩短趋势相关（加权平均差 -42.4小时，95%可信区间 -94.4，9.6）。HFPPV和触发通气均与BPD发生率显著降低无关。使用HFPPV与CMV相比死亡率有非显著降低趋势，使用触发通气与CMV相比死亡率有非显著升高趋势。关于其他结局，未发现HFPPV或触发通气有不利影响。自上次综述以来，纳入了两种新的患者触发模式：压力调节容量控制通气（PRVCV）和SIMV加压力支持。这些通气方法中的每一种仅在单个随机试验中进行了测试，在重要结局方面没有显著优势。
与传统通气相比，HFPPV和触发通气分别在减少气漏和缩短通气时间方面显示出益处。在任何试验中均未进行复杂的呼吸监测，因此无法得出产生这些益处的机制是通过引发同步通气的结论。需要进一步试验以确定同步通气是否与其他益处相关，但在开展进一步试验之前，鼓励在呼吸诊断方面优化触发和呼吸机设计。在将新型触发通气形式纳入常规临床实践之前，必须在有足够样本量且有长期结局的随机试验中对其进行测试。
