Association Between Use of Lung-Protective Ventilation With Lower Tidal Volumes and Clinical Outcomes Among Patients Without Acute Respiratory Distress Syndrome A Meta-analysis Protective Ventilation and Lower Tidal Volumes

Serpa Neto A, Cardoso S, Manetta J, et al. — Wed, 24 Oct 2012 00:00:00 GMT

Context

Lung-protective mechanical ventilation with the use of lower tidal volumes has been found to improve outcomes of patients with acute respiratory distress syndrome (ARDS). It has been suggested that use of lower tidal volumes also benefits patients who do not have ARDS.

Objective

To determine whether use of lower tidal volumes is associated with improved outcomes of patients receiving ventilation who do not have ARDS.

Data Sources

MEDLINE, CINAHL, Web of Science, and Cochrane Central Register of Controlled Trials up to August 2012.

Study Selection

Eligible studies evaluated use of lower vs higher tidal volumes in patients without ARDS at onset of mechanical ventilation and reported lung injury development, overall mortality, pulmonary infection, atelectasis, and biochemical alterations.

Data Extraction

Three reviewers extracted data on study characteristics, methods, and outcomes. Disagreement was resolved by consensus.

Data Synthesis

Twenty articles (2822 participants) were included. Meta-analysis using a fixed-effects model showed a decrease in lung injury development (risk ratio [RR], 0.33; 95% CI, 0.23 to 0.47; I², 0%; number needed to treat [NNT], 11), and mortality (RR, 0.64; 95% CI, 0.46 to 0.89; I², 0%; NNT, 23) in patients receiving ventilation with lower tidal volumes. The results of lung injury development were similar when stratified by the type of study (randomized vs nonrandomized) and were significant only in randomized trials for pulmonary infection and only in nonrandomized trials for mortality. Meta-analysis using a random-effects model showed, in protective ventilation groups, a lower incidence of pulmonary infection (RR, 0.45; 95% CI, 0.22 to 0.92; I², 32%; NNT, 26), lower mean (SD) hospital length of stay (6.91 [2.36] vs 8.87 [2.93] days, respectively; standardized mean difference [SMD], 0.51; 95% CI, 0.20 to 0.82; I², 75%), higher mean (SD) PaCO₂ levels (41.05 [3.79] vs 37.90 [4.19] mm Hg, respectively; SMD, −0.51; 95% CI, −0.70 to −0.32; I², 54%), and lower mean (SD) pH values (7.37 [0.03] vs 7.40 [0.04], respectively; SMD, 1.16; 95% CI, 0.31 to 2.02; I², 96%) but similar mean (SD) ratios of PaO₂ to fraction of inspired oxygen (304.40 [65.7] vs 312.97 [68.13], respectively; SMD, 0.11; 95% CI, −0.06 to 0.27; I², 60%). Tidal volume gradients between the 2 groups did not influence significantly the final results.

Conclusions

Among patients without ARDS, protective ventilation with lower tidal volumes was associated with better clinical outcomes. Some of the limitations of the meta-analysis were the mixed setting of mechanical ventilation (intensive care unit or operating room) and the duration of mechanical ventilation.

Low Tidal Volumes for All?

Ferguson ND. — Wed, 24 Oct 2012 00:00:00 GMT

Clinicians are continually striving to improve the quality of care in medicine. In the intensive care unit (ICU) environment, the focus on quality has been on avoidance of iatrogenic complications. Mechanical ventilation provides a specific example; treatment goals have changed remarkably in the last 20 years—from maintaining “normal” blood gas values to supporting acceptable gas exchange while avoiding or minimizing ventilator-induced lung injury. Previously, ventilator-induced lung injury was only recognized when overt barotrauma such as pneumothorax occurred. Today, however, a more insidious form of ventilator-induced lung injury is recognized, one that arises through cyclic alveolar over-distension (volutrauma) and other mechanisms and can produce local and systemic inflammatory reactions leading to multiorgan failure and death. The National Heart, Lung, and Blood Institute Acute Respiratory Distress Syndrome Network clinical trial demonstrated that the use of low tidal volumes in patients with established acute respiratory distress syndrome (ARDS) results in a considerable reduction in mortality. Until now, the focus of lung-protective ventilation has remained on treatment of ARDS.

JAMA: Acute Lung Injury/Acute Respiratory Failure Topic Collection

Association Between Use of Lung-Protective Ventilation With Lower Tidal Volumes and Clinical Outcomes Among Patients Without Acute Respiratory Distress Syndrome A Meta-analysis Protective Ventilation and Lower Tidal Volumes

Low Tidal Volumes for All?