Petrucci N, Iacovelli W
Department of Anaesthesia and Intensive care, Azienda Ospedaliera Desenzano, Loc. Montecroce, Desenzano (BS), Italy.
Cochrane Database Syst Rev. 2003(3):CD003844. doi: 10.1002/14651858.CD003844.
Patients with acute respiratory distress syndrome (ARDS) and acute lung injury (ALI) require mechanical ventilatory support. ALI/ARDS is further complicated by ventilator-induced lung injury. Lung-protective ventilation strategies may lead to improved survival.
To assess the effects of ventilation with lower tidal volume (Vt) on morbidity and mortality in adults patients affected by ALI/ARDS. A secondary objective was to determine whether the comparison between low and conventional Vt is different if a plateau airway pressure of greater than 30 to 35 cm H20 was used.
We searched The Cochrane Central Register of Controlled Trials (CENTRAL), The Cochrane Library issue 3, 2002; MEDLINE (1966 to June 2002); EMBASE and CINAHL (1982 to June 2002); intensive care journals and conference proceedings; databases of ongoing research, reference lists and 'grey literature'.
Randomized trials comparing ventilation using lower Vt and/or low airway driving pressure (plateau pressure 30 cm H2O or less), resulting in Vt of 7 ml/kg or less versus ventilation that uses Vt in the range of 10 to 15 ml/kg, in adults (16 year-old or greater).
Two reviewers independently assessed trial quality and extracted data. Wherever appropriate, results were pooled. Fixed and random effects models were applied.
Five trials, involving 1202 patients, were eligible. The test for heterogeneity gave a P-value of 0.12. Ventilation with lower Vt was associated with a decreased mortality at the end of the follow up period for each trial: 216/605 (35.7%) versus 249/597 (41.7%), relative risk (RR) 0.85 (CI 0.74 to 0.98). The effect of the intervention was not statistically significant when a random effects model was used: RR 0.91 (CI 0.72 to 1.14). Mortality at day 28 was significantly reduced by lung-protective ventilation: RR 0.74 (CI 0.61 to 0.88). The comparison between low and conventional Vt was not significantly different if a plateau pressure less than or equal to 31 cm H2O in control group was used: RR 1.13 (CI 0.88 to 1.45). There was insufficient evidence about morbidity and long term outcomes.
REVIEWER'S CONCLUSIONS: Clinical heterogeneity, such as different lengths of follow up and higher plateau pressure in control arms in two trials make the interpretation of the combined results difficult. Mortality is significantly reduced at day 28 and the effects on long term mortality are uncertain, although the possibility of a clinically relevant benefit cannot be excluded. There is no evidence that low Vt ventilation is beneficial in patients where hypercapnia is potentially harmful.
急性呼吸窘迫综合征（ARDS）和急性肺损伤（ALI）患者需要机械通气支持。ALI/ARDS会因呼吸机诱导的肺损伤而进一步恶化。肺保护性通气策略可能会提高生存率。
评估低潮气量（Vt）通气对ALI/ARDS成年患者发病率和死亡率的影响。第二个目的是确定如果使用大于30至35 cm H₂O的平台气道压，低Vt与传统Vt之间的比较是否会有所不同。
我们检索了Cochrane对照试验中心注册库（CENTRAL）、2002年第3期《Cochrane图书馆》；MEDLINE（1966年至2002年6月）；EMBASE和CINAHL（1982年至2002年6月）；重症监护期刊和会议论文集；正在进行的研究数据库、参考文献列表和“灰色文献”。
比较使用较低Vt和/或低气道驱动压（平台压30 cm H₂O或更低）导致Vt为7 ml/kg或更低的通气与使用10至15 ml/kg范围内Vt的通气的随机试验，受试者为成年人（16岁及以上）。
两名评价员独立评估试验质量并提取数据。在适当情况下，合并结果。应用固定效应模型和随机效应模型。
五项试验符合要求，涉及1202名患者。异质性检验的P值为0.12。在每项试验的随访期末，较低Vt通气与死亡率降低相关：216/605（35.7%）对249/597（41.7%），相对危险度（RR）0.85（95%CI 0.74至0.98）。使用随机效应模型时，干预效果无统计学意义：RR 0.91（95%CI 0.72至1.14）。肺保护性通气显著降低了第28天的死亡率：RR 0.74（95%CI 0.61至0.88）。如果对照组的平台压小于或等于31 cm H₂O，低Vt与传统Vt之间的比较无显著差异：RR 1.13（95%CI 0.88至1.45）。关于发病率和长期结局的证据不足。
临床异质性，如两项试验中随访时间不同以及对照组平台压较高，使得对合并结果的解释困难。第28天死亡率显著降低，对长期死亡率的影响尚不确定，尽管不能排除具有临床意义的益处的可能性。没有证据表明低Vt通气对高碳酸血症可能有害的患者有益。
