Effect of lung-protective ventilation with lower tidal volumes on clinical outcomes among patients undergoing surgery: a meta-analysis of randomized controlled trials

Abstract

Background: In anesthetized patients undergoing surgery, the role of lung-protective ventilation with lower tidal volumes is unclear. We performed a meta-analysis of randomized controlled trials (RCTs) to evaluate the effect of this ventilation strategy on postoperative outcomes.

Methods: We searched electronic databases from inception through September 2014. We included RCTs that compared protective ventilation with lower tidal volumes and conventional ventilation with higher tidal volumes in anesthetized adults undergoing surgery. We pooled outcomes using a random-effects model. The primary outcome measures were lung injury and pulmonary infection.

Results: We included 19 trials (n=1348). Compared with patients in the control group, those who received lung-protective ventilation had a decreased risk of lung injury (risk ratio [RR] 0.36, 95% confidence interval [CI] 0.17 to 0.78; I2=0%) and pulmonary infection (RR 0.46, 95% CI 0.26 to 0.83; I2=8%), and higher levels of arterial partial pressure of carbon dioxide (standardized mean difference 0.47, 95% CI 0.18 to 0.75; I2=65%). No significant differences were observed between the patient groups in atelectasis, mortality, length of hospital stay, length of stay in the intensive care unit or the ratio of arterial partial pressure of oxygen to fraction of inspired oxygen.

Interpretation: Anesthetized patients who received ventilation with lower tidal volumes during surgery had a lower risk of lung injury and pulmonary infection than those given conventional ventilation with higher tidal volumes. Implementation of a lung-protective ventilation strategy with lower tidal volumes may lower the incidence of these outcomes.

Figure 1:

Selection of randomized controlled trials (RCTs) for the meta-analysis.

Figure 2:

Appraisal of risk of bias of the included trials using the Cochrane risk-of-bias tool. Low risk = bias, if present, is unlikely to alter the results seriously, unclear risk = bias raises some doubt about the results, high risk = bias may alter the results seriously.

Figure 3:

Effect of lung-protective ventilation with lower tidal volumes on lung injury and pulmonary infection among patients undergoing surgery. A risk ratio less than 1.0 indicates an effect in favour of lung-protective ventilation. CI = confidence interval, V_T = tidal volume.

Figure 4:

Effect of lung-protective ventilation with lower tidal volumes on atelectasis and mortality among patients undergoing surgery. A risk ratio less than 1.0 indicates an effect in favour of lung-protective ventilation. CI = confidence interval, V_T = tidal volume.

Figure 5:

Effect of lung-protective ventilation with lower tidal volumes on length of stay in hospital and in intensive care unit (ICU) among patients undergoing surgery. A standardized mean difference (SMD) less than zero indicates an effect in favour of lung-protective ventilation. CI = confidence interval, V_T = tidal volume.

Figure 6:

Effect of lung-protective ventilation with lower tidal volumes on the Pao₂/Fio₂ ratio (normal 400–500 mm Hg) and the Paco₂ level (normal 35–45 mm Hg) among patients undergoing surgery. A standardized mean difference (SMD) greater than zero indicates an effect in favour of lung-protective ventilation. CI = confidence interval, Fio₂ = fraction of inspired oxygen, Paco₂ = arterial partial pressure of carbon dioxide, Pao₂ = arterial partial pressure of oxygen, V_T = tidal volume.