Ventilation with lower tidal volumes versus traditional tidal volumes in adults for acute lung injury and acute respiratory distress syndrome.

BACKGROUND: Patients with acute respiratory distress syndrome and acute lung injury require mechanical ventilatory support. Acute respiratory distress syndrome and acute lung injury are further complicated by ventilator-induced lung injury. Lung-protective ventilation strategies may lead to improved survival.
OBJECTIVES: To assess the effects of ventilation with lower tidal volume on morbidity and mortality in patients aged 16 years or older affected by acute respiratory distress syndrome and acute lung injury. A secondary objective was to determine whether the comparison between low and conventional tidal volume was different if a plateau airway pressure of greater than 30 to 35 cm H20 was used. SEARCH STRATEGY: We searched The Cochrane Central Register of Controlled Trials (CENTRAL), The Cochrane Library issue 4, 2003; MEDLINE (1966 to October 2003); EMBASE and CINAHL (1982 to October 2003); intensive care journals and conference proceedings; databases of ongoing research, reference lists and 'grey literature'. SELECTION CRITERIA: Randomized trials comparing ventilation using either lower tidal volume or low airway driving pressure (plateau pressure 30 cm H(2)O or less), resulting in tidal volume of 7 ml/kg or less versus ventilation that uses Vt in the range of 10 to 15 ml/kg, in adults (aged 16 years or older). DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed trial quality and extracted data. Wherever appropriate, results were pooled. Fixed and random effects models were applied. MAIN
RESULTS: Five trials, involving 1202 patients, were eligible. Mortality at day 28 was significantly reduced by lung-protective ventilation: relative risk 0.74 (confidence interval 0.61 to 0.88), whereas beneficial effect on long-term mortality was uncertain: relative risk 0.84 (confidence interval 0.68 to 1.05). The comparison between low and conventional tidal volume was not significantly different if a plateau pressure less than or equal to 31 cm H2O in control group was used: relative risk 1.13 (confidence interval 0.88 to 1.45). There was insufficient evidence about morbidity and long term outcomes. REVIEWERS'
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.