Recruitment manoeuvres as a ventilation strategy for adults with acute respiratory failure due to lung injury

Background: Acute respiratory failure is a common condition amongst adults admitted to intensive care units (ICUs) worldwide. Although respiratory failure has many causes, it may be due to a condition known as acute respiratory distress syndrome (ARDS). This term describes a condition in which both of the lungs have become injured and inflamed from one of various causes, and they do not work as they normally would to provide oxygen to and remove carbon dioxide from the body. This leads to a reduced amount of oxygen in the blood. Patients may require connection to a ventilator (breathing machine) to support their breathing. This therapy is known as mechanical ventilation. Supportive care with mechanical ventilation is an important pillar of standard treatment for patients with ARDS.

Although it may be life-saving, mechanical ventilation may further contribute to lung injury by expanding and collapsing the lungs or overstretching lung tissue. To minimize damage to injured lungs, smaller volumes of air at lower pressures have been used in conjunction with a positive opening pressure at the end of expiration (PEEP). This ventilation strategy has been shown to shorten the time that patients require mechanical ventilation while improving survival; it has been adopted as standard care for patients with ARDS who are in intensive care.

Along with this strategy, additional ventilation techniques have been developed. One such technique is known as a recruitment manoeuvre; when combined with higher PEEP, it is called the open lung ventilation strategy. A recruitment manoeuvre uses sustained deep breaths to assist in the recruitment - or re-opening - of collapsed lung units. This may increase the number of lung units available for breathing and may improve patient outcomes. Effects of recruitment manoeuvres have not been well established.

Search date: Evidence is current to August 2016.

Study characteristics: We included 10 trials in this review, which included a total of 1658 participants with acute respiratory distress syndrome.

Key results: Low-quality evidence suggests that recruitment manoeuvres improve ICU survival but not 28-day or hospital survival. Recruitment manoeuvres have no effect on the risk of air leakage from the lungs.

Quality of the evidence: We found the evidence for most outcomes to be of low to moderate quality, primarily because of the design of included trials. Many trials used the recruitment manoeuvre in conjunction with other ventilation techniques or strategies, and this might have influenced outcomes. Caution should be applied when conclusions are drawn about the effectiveness of the recruitment manoeuvre alone.

Authors' conclusions: 

We identified significant clinical heterogeneity in the 10 included trials. Results are based upon the findings of several (five) trials that included an "open lung ventilation strategy", whereby the intervention group differed from the control group in aspects other than the recruitment manoeuvre (including co-interventions such as higher PEEP, different modes of ventilation and higher plateau pressure), making interpretation of the results difficult. A ventilation strategy that included recruitment manoeuvres in participants with ARDS reduced intensive care unit mortality without increasing the risk of barotrauma but had no effect on 28-day and hospital mortality. We downgraded the quality of the evidence to low, as most of the included trials provided co-interventions as part of an open lung ventilation strategy, and this might have influenced results of the outcome.

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Background: 

Recruitment manoeuvres involve transient elevations in airway pressure applied during mechanical ventilation to open (‘recruit’) collapsed lung units and increase the number of alveoli participating in tidal ventilation. Recruitment manoeuvres are often used to treat patients in intensive care who have acute respiratory distress syndrome (ARDS), but the effect of this treatment on clinical outcomes has not been well established. This systematic review is an update of a Cochrane review originally published in 2009.

Objectives: 

Our primary objective was to determine the effects of recruitment manoeuvres on mortality in adults with acute respiratory distress syndrome.

Our secondary objective was to determine, in the same population, the effects of recruitment manoeuvres on oxygenation and adverse events (e.g. rate of barotrauma).

Search strategy: 

For this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OVID), Embase (OVID), the Cumulative Index to Nursing and Allied Health Literature (CINAHL, EBSCO), Latin American and Caribbean Health Sciences (LILACS) and the International Standard Randomized Controlled Trial Number (ISRCTN) registry from inception to August 2016.

Selection criteria: 

We included randomized controlled trials (RCTs) of adults who were mechanically ventilated that compared recruitment manoeuvres versus standard care for patients given a diagnosis of ARDS.

Data collection and analysis: 

Two review authors independently assessed trial quality and extracted data. We contacted study authors for additional information.

Main results: 

Ten trials met the inclusion criteria for this review (n = 1658 participants). We found five trials to be at low risk of bias and five to be at moderate risk of bias. Six of the trials included recruitment manoeuvres as part of an open lung ventilation strategy that was different from control ventilation in aspects other than the recruitment manoeuvre (such as mode of ventilation, higher positive end-expiratory pressure (PEEP) titration and lower tidal volume or plateau pressure). Six studies reported mortality outcomes. Pooled data from five trials (1370 participants) showed a reduction in intensive care unit (ICU) mortality (risk ratio (RR) 0.83, 95% confidence interval (CI) 0.72 to 0.97, P = 0.02, low-quality evidence), pooled data from five trials (1450 participants) showed no difference in 28-day mortality (RR 0.86, 95% CI 0.74 to 1.01, P = 0.06, low-quality evidence) and pooled data from four trials (1313 participants) showed no difference in in-hospital mortality (RR 0.88, 95% CI 0.77 to 1.01, P = 0.07, low-quality evidence). Data revealed no differences in risk of barotrauma (RR 1.09, 95% CI 0.78 to 1.53, P = 0.60, seven studies, 1508 participants, moderate-quality evidence).

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