Clinical review: the implications of experimental and clinical studies of recruitment maneuvers in acute lung injury

Aggressive alveolar recruitment in ARDS: More shadows than lights

Alveolar recruitment in acute respiratory distress syndrome (ARDS) is defined as the penetration of gas into previously unventilated areas or poorly ventilated areas. Alveolar recruitment during recruitment maneuvering (RM) depends on the duration of the maneuver, the recruitable lung tissue, and the balance between the recruitment of collapsed areas and over-insufflation of the ventilated areas. Alveolar recruitment is estimated using computed tomography of the lung and, at the patient bedside, through assessment of the recruited volume using pressure-volume curves and assessing lung morphology with pulmonary ultrasound and/or impedance tomography. The scientific evidence on RM in patients with ARDS remains subject to controversy. Randomized studies on ARDS have shown no benefit or have even reflected an increase in mortality. The routine use of RM is therefore not recommended.

Recruitment manoeuvres for adults with acute respiratory distress syndrome receiving mechanical ventilation

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 METHODS

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).

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.

Efficacy of Alveolar Recruitment Maneuvers in Patients With Complicated Thoracic Trauma

The objective of this study was to measure the efficacy of biphasic positive airway pressure (BIPAP) and synchronized intermittent mandatory ventilation (SIMV) with alveolar recruitment maneuvers (ARMs) in patients with acute lung injury (ALI) and concomitant pneumothorax. Seventy-four patients with ALI and concomitant pneumothorax secondary to blunt thoracic injury were studied. All patients fulfilled criteria for the first stage of acute respiratory distress syndrome, which consisted of acute onset dyspnea, isolated rales, an extravascular lung water index >7 mL/kg, and an oxygenation index <300 mm Hg in the absence of left-ventricular dysfunction. After evacuation of the pneumothorax, ARMs were performed using BIPAP or SIMV 3 to 5 times a day with a peak pressure of 33.4 ± 0.2 cm H2O and a positive end-expiratory pressure of 16.1 ± 0.2 cm H2O. The use of BIPAP in patients with ALI and concomitant pneumothorax reduced the time to resolution of the air leak allowing application of earlier ARMs. ARMs with peak pressures of 35 to 40 cm H2O effectively improved oxygenation and biomechanical properties of the lungs and did not cause pneumothorax relapse. In conclusion, BIPAP allowed for spontaneous ventilation during the breathing cycle and limited Ppeak. Its use was associated with more rapid sealing of air leaks with the ability to conduct earlier ARMs. The use of BIPAP compared with SIMV improved outcome in the presence of complex thoracic trauma.

Changes of splanchnic perfusion after applying positive end expiratory pressure in patients with acute respiratory distress syndrome

Background:

Positive end-expiratory pressure (PEEP) improves oxygenation and can prevent ventilator- induced lung injury in patients with acute respiratory distress syndrome (ARDS). Nevertheless, PEEP can also induce detrimental effects by its influence on the cardiovascular system. The purpose of this study was to assess the effects of PEEP on gastric mucosal perfusion while applying a protective ventilatory strategy in patients with ARDS.

Materials and Methods:

Thirty-two patients were included in the study. A pressure–volume curve was traced and ideal PEEP, defined as lower inflection point + 2cmH₂O, was determined. Gastric tonometry was measured continuously (Tonocap). After baseline measurements, 10, 15 and 20cmH₂O PEEP and ideal PEEP were applied for 30 min each. By the end of each period, hemodynamics, CO₂ gap (gastric minus arterial partial pressures), and ventilatory measurements were taken.

Results:

PEEP had no effect on CO₂ gap (median [range], baseline: 18 [2–30] mmHg; PEEP 10: 18 [0–40] mmHg; PEEP 15: 17 [0–39] mmHg; PEEP 20: 16 [4–39] mmHg; ideal PEEP: 19 [9–39] mmHg; P = 0.19). Cardiac index also remained unchanged (baseline: 4.7 [2.6–6.2] l min⁻¹ m⁻²; PEEP 10: 4.4 [2.5–7] l min⁻¹ m⁻²; PEEP 15: 4.4 [2.2–6.8] l min⁻¹ m⁻²; PEEP 20: 4.8 [2.4–6.3] l min⁻¹ m⁻²; ideal PEEP: 4.9 [2.4–6.3] l min⁻¹ m⁻²; P = 0.09).

Conclusion:

PEEP of 10–20 cmH₂O does not affect splanchnic perfusion and is hemodynamically well tolerated in most patients with ARDS, including those receiving inotropic supports.

Alveolar recruitment maneuvers in acute lung injury/acute respiratory distress syndrome

Mechanical ventilation can worsen lung damage in acute lung injury and acute respiratory distress syndrome. The use of low tidal volumes is one of the strategies that has been shown to reduce lung injury and improve outcomes in this situation. However, low tidal volumes may lead to alveolar derecruitment and worsening of hypoxia. Recruitment maneuvers along with positive end-expiratory pressure may help to prevent derecruitment. Although recruitment maneuvers have been shown to improve oxygenation, improved clinical outcomes have not been demonstrated. The optimal recruitment strategy and the type of patients who might benefit are also unclear. This review summarizes the impact of recruitment maneuvers on lung mechanics and physiology, techniques of application, and the clinical situations in which they may be useful.

A recruitment maneuver increases oxygenation after intubation of hypoxemic intensive care unit patients: a randomized controlled study

Introduction

Tracheal intubation and anaesthesia promotes lung collapse and hypoxemia. In acute lung injury patients, recruitment maneuvers (RMs) increase lung volume and oxygenation, and decrease atelectasis. The aim of this study was to evaluate the efficacy and safety of RMs performed immediately after intubation.

Methods

This randomized controlled study was conducted in two 16-bed medical-surgical intensive care units within the same university hospital. Consecutive patients requiring intubation for acute hypoxemic respiratory failure were included. Patients were randomized to undergo a RM immediately (within 2 minutes) after intubation, consisting of a continuous positive airway pressure (CPAP) of 40 cmH₂O over 30 seconds (RM group), or not (control group). Blood gases were sampled and blood samples taken for culture before, within 2 minutes, 5 minutes, and 30 minutes after intubation. Haemodynamic and respiratory parameters were continuously recorded throughout the study. Positive end expiratory pressure (PEEP) was set at 5 cmH₂O throughout.

Results

The control (n = 20) and RM (n = 20) groups were similar in terms of age, disease severity, diagnosis at time of admission, and PaO₂ obtained under 10-15 L/min oxygen flow immediately before (81 ± 15 vs 83 ± 35 mmHg, P = 0.9), and within 2 minutes after, intubation under 100% FiO₂ (81 ± 15 vs 83 ± 35 mmHg, P = 0.9). Five minutes after intubation, PaO₂ obtained under 100% FiO₂ was significantly higher in the RM group compared with the control group (93 ± 36 vs 236 ± 117 mmHg, P = 0.008). The difference remained significant at 30 minutes with 110 ± 39 and 180 ± 79 mmHg, respectively, for the control and RM groups. No significant difference in haemodynamic conditions was observed between groups at any time. Following tracheal intubation, 15 patients had positive blood cultures, showing microorganisms shared with tracheal aspirates, with no significant difference in the incidence of culture positivity between groups.

Conclusions

Recruitment maneuver following intubation in hypoxemic patients improved short-term oxygenation, and was not associated with increased adverse effects.

Trial registration

NCT01014299

Recruitment manoeuvres for adults with acute lung injury receiving mechanical ventilation

BACKGROUND

Recruitment manoeuvres are often used to treat patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) but the effect of this treatment on clinical outcomes has not been well established.

OBJECTIVES

The objective of this review was to examine recruitment manoeuvres compared to standard care as therapy for adults with acute lung injury in order to quantify the effects on patient outcomes (mortality, length of ventilation, and other relevant outcomes).

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, Issue 2); MEDLINE (January 1966 to May 2008); EMBASE (January 1980 to May 2008); LILACS (1982 to May 2008); CINAHL (1982 to May 2008); and Current Controlled Trials (www.controlled-trials.com).

SELECTION CRITERIA

We included randomized controlled trials of adults who were mechanically ventilated comparing recruitment manoeuvres to standard care for those patients diagnosed with ALI or ARDS.

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

Seven trials met the inclusion criteria for this review (the total number of included participants was 1170). All trials included a recruitment manoeuvre as part of the treatment strategy for patients on mechanical ventilation for ARDS or ALI. However, two of the trials included a package of ventilation that was different from the control ventilation in aspects other than the recruitment manoeuvre. The intervention group showed no significant difference on 28-day mortality (RR 0.73, 95% CI 0.46 to 1.17, P = 0.2). Similarly there was no statistical difference for risk of barotrauma (RR 0.50, 95% CI 0.07 to 3.52, P = 0.5) or blood pressure (MD 0.9 mm Hg, 95% CI -4.28 to 6.08, P = 0.73). Recruitment manoeuvres significantly increased oxygenation above baseline levels for a short period of time in four of the five studies that measured oxygenation. There were insufficient data on length of ventilation or hospital stay to pool results.

AUTHORS' CONCLUSIONS

There is not evidence to make conclusions on whether recruitment manoeuvres reduce mortality or length of ventilation in patients with ALI or ARDS.

Effects of frequency and inspiratory plateau pressure during recruitment manoeuvres on lung and distal organs in acute lung injury

PURPOSE

To evaluate the effects of frequency and inspiratory plateau pressure (Pplat) during recruitment manoeuvres (RMs) on lung and distal organs in acute lung injury (ALI).

METHODS

We studied paraquat-induced ALI rats. At 24 h, rats were anesthetized and RMs were applied using continuous positive airway pressure (CPAP, 40 cmH(2)O/40 s) or three-different sigh strategies: (a) 180 sighs/h and Pplat = 40 cmH(2)O (S180/40), (b) 10 sighs/h and Pplat = 40 cmH(2)O (S10/40), and (c) 10 sighs/h and Pplat = 20 cmH(2)O (S10/20).

RESULTS

S180/40 yielded alveolar hyperinflation and increased lung and kidney epithelial cell apoptosis as well as type III procollagen (PCIII) mRNA expression. S10/40 resulted in a reduction in epithelial cell apoptosis and PCIII expression. Static elastance and alveolar collapse were higher in S10/20 than S10/40.

CONCLUSIONS

The reduction in sigh frequency led to a protective effect on lung and distal organs, while the combination with reduced Pplat worsened lung mechanics and histology.

[Hemodynamic variability caused by pressure-volume plotting and alveolar recruitment maneuvers in patients with adult respiratory distress syndrome]

OBJECTIVES

The plotting of pressure-volume curves and the performance of alveolar recruitment maneuvers are common practices in the care of patients with adult respiratory distress syndrome (ARDS), even though potentially harmful hemodynamic effects are associated with sustaining a high intrathoracic pressure. Our aim was to analyze hemodynamic and ventilatory changes related to these 2 maneuvers and to assess the short-term effectiveness of recruitment.

PATIENTS AND METHODS

The patients had ARDS and were being monitored with a catheter connected to a PiCCO system. All measurements were taken in sinus rhythm and with adequate vascular filling. Values recorded during plotting of the quasistatic pressure-volume curve and the recruitment maneuver (sustained airway pressure of 40 cm H2O) were the cardiac index, mean arterial pressure, heart rate, systolic volume index, and oxygen saturation (SpO2). Blood gas measurements were recorded before the maneuvers and 15 minutes afterwards.

RESULTS

All parameters decreased significantly in the 14 patients studied. The mean (SD) maximum decreases, from which all patients recovered within 2 minutes, were as follows: cardiac index, 26% (16%); mean arterial pressure, 6% (6%); heart rate, 4% (5%), systolic volume index, 21% (15%); and SpO2, 3% (3%). Significant increases in PaO2 (7% [6%]) and the ratio of PaO2 to the fraction of inspired oxygen were recorded after the recruitment maneuver (P=.016 and P=.014, respectively), but the changes were not clinically significant.

CONCLUSIONS

The hemodynamic disturbances associated with the alveolar recruitment maneuver based on sustaining a high end-expiratory pressure and the minor improvement in oxygenation achieved as a result suggest that the routine use of that maneuver in ARDS patients is of questionable value.

Hochfrequenz-Oszillations-Ventilation

The concept of lung protective ventilation strategies is based on the limitation of the inspiratory pressure and the reduction of the tidal volume, in order to minimize the extent of breathing cycle-dependent damaging mechanisms from mechanical ventilation. This concept is coupled with various procedures for optimization of the end-expiratory lung volume in acute lung failure in order to improve the compromized oxygenation. In this situation high-frequency oscillatory ventilation (HFOV) has achieved a renaissance. Theoretically this procedure offers advantages which differentiates it from conventional ventilation procedures. The system allows the use of a constant higher mean airway pressure, a reduction of the peak pressure and the use of a tidal volume in the dead-space area. Very little data exist with respect to the application of this procedure in adult patients. For the clinical use of HFOV as a secondary procedure in adult patients suffering from acute lung failure it could be demonstrated that it is a safe and effective method of treatment. The effect of HFVO on the morbidity and mortality outcome, however, still needs to be characterized.

The Mapleson C circuit clears more secretions than the Laerdal circuit during manual hyperinflation in mechanically-ventilated patients: a randomised cross-over trial

QUESTION

What is the effect of the Mapleson C circuit compared with the Laerdal circuit in removing secretions and improving ventilation and gas exchange during manual hyperinflation?

DESIGN

Prospective, randomised, cross-over trial.

PARTICIPANTS

Twenty patients from a tertiary-level intensive care unit who were being mechanically ventilated.

INTERVENTION

Manual hyperinflation in side-lying with both the Mapleson C or Laerdal circuit on the one day, one circuit in the morning and one in the afternoon, with a washout period of at least three hours between them.

OUTCOME MEASURES

Secretion clearance was measured as sputum weight, ventilation was measured as respiratory compliance and tidal volume, while gas exchange was measured as oxygenation and CO2 removal.

RESULTS

The Mapleson C circuit cleared 0.89 g (95% CI 0.80 to 1.15) more secretions than the Laerdal circuit (p < 0.02). There was no difference between the Mapleson C and the Laerdal circuits on respiratory compliance (p = 0.81), tidal volume (p = 0.45), oxygenation (p = 0.28), or CO2 removal (p = 0.17).

CONCLUSION

Although more secretions were cleared using the Mapleson C compared with the Laerdal circuit in this study, this had no consequence in terms of oxygenation and compliance only trended to improve. As the study was underpowered the clinical significance of these findings is not clear.

Lung mechanics at the bedside: make it simple

PURPOSE OF REVIEW

The aim of this review is to describe ventilator-patient interaction, employing the equation of motion and the curves obtained by the ventilator. Practitioners confronted with mechanically ventilated patients every day in intensive care units should be able to sort out from all data available from modern ventilators those relevant for choosing a correct ventilatory strategy for each patient.

RECENT FINDINGS

Early determination of patient-ventilator asynchrony, air-leaks and variation in respiratory parameters is important during mechanical ventilation. A correct evaluation of data, for patient safety and tailored ventilatory strategy becomes mandatory when non-invasive ventilation by helmet or mask is applied.

SUMMARY

The equation of motion is described and dynamic and static respiratory mechanics are analysed to highlight all those data that can influence decision-making in setting mechanical or assisted ventilation in invasively and non-invasively ventilated patients.

[Abdominal compartment syndrome: significance, diagnosis and treatment]

A pathological increase of intraabdominal pressure (IAP) is frequently observed in severely ill patients suffering from surgical diseases. This may lead to the abdominal compartment syndrome (ACS) which is characterized by an IAP >20 mmHg (>2.67 kPa) and failure of one or more organ systems. The mortality of ACS exceeds 60%. Knowledge concerning the sequelae of ACS is abundant, however, measurement of IAP is not routinely performed even if patients present with corresponding risk factors. This is probably due to a variable incidence of ACS and scepticism regarding the results of bladder pressure measurement. However, measurement of IAP can now be performed semi-automatically, continuously and in a standardized fashion. The therapy of ACS, i.e. decompression laparotomy and laparostomy, is undisputed. Since a heterogeneous group of patients can be affected, monitoring of IAP is indicated in patients needing intensive care. A consistent registration of IAP will improve knowledge and guidelines regarding the therapy of a pathologically increased IAP. Nevertheless, patients in whom ACS is suspected should be decompressed as soon as possible.

Lung recruitment in patients with the acute respiratory distress syndrome

BACKGROUND

In the acute respiratory distress syndrome (ARDS), positive end-expiratory pressure (PEEP) may decrease ventilator-induced lung injury by keeping lung regions open that otherwise would be collapsed. Since the effects of PEEP probably depend on the recruitability of lung tissue, we conducted a study to examine the relationship between the percentage of potentially recruitable lung, as indicated by computed tomography (CT), and the clinical and physiological effects of PEEP.

METHODS

Sixty-eight patients with acute lung injury or ARDS underwent whole-lung CT during breath-holding sessions at airway pressures of 5, 15, and 45 cm of water. The percentage of potentially recruitable lung was defined as the proportion of lung tissue in which aeration was restored at airway pressures between 5 and 45 cm of water.

RESULTS

The percentage of potentially recruitable lung varied widely in the population, accounting for a mean (+/-SD) of 13+/-11 percent of the lung weight, and was highly correlated with the percentage of lung tissue in which aeration was maintained after the application of PEEP (r2=0.72, P<0.001). On average, 24 percent of the lung could not be recruited. Patients with a higher percentage of potentially recruitable lung (greater than the median value of 9 percent) had greater total lung weights (P<0.001), poorer oxygenation (defined as a ratio of partial pressure of arterial oxygen to fraction of inspired oxygen) (P<0.001) and respiratory-system compliance (P=0.002), higher levels of dead space (P=0.002), and higher rates of death (P=0.02) than patients with a lower percentage of potentially recruitable lung. The combined physiological variables predicted, with a sensitivity of 71 percent and a specificity of 59 percent, whether a patient's proportion of potentially recruitable lung was higher or lower than the median.

CONCLUSIONS

In ARDS, the percentage of potentially recruitable lung is extremely variable and is strongly associated with the response to PEEP.

Lung recruitment during mechanical positive pressure ventilation in the PICU: what can be learned from the literature?

A literature review was conducted to assess the evidence for recruitment manoeuvres used in conventional mechanical positive pressure ventilation. A total of 61 studies on recruitment manoeuvres were identified: 13 experimental, 31 ICU, 6 PICU and 12 anaesthesia studies. Recruitment appears to be a continuous process during inspiration and expiration and is determined by peak inspiratory pressure (PIP) and positive end expiratory pressure (PEEP). Single or repeated recruitment manoeuvres may result in a statistically significant increase in oxygenation; however, this is short lasting and clinically irrelevant, especially in late ARDS and pneumonia. Temporary PIP elevation may be effective but only after PEEP loss (for example disconnection and tracheal suctioning). Continuous PEEP elevation and prone positioning can increase P(a)O2 significantly. Adverse haemodynamic or barotrauma effects are reported in various studies. No data exist on the effect of recruitment manoeuvres on mortality, morbidity, length of stay or duration of mechanical ventilation. Although recruitment manoeuvres can improve oxygenation, they can potentially increase lung injury, which eventually determines outcome. Based on the presently available literature, prone position and sufficient PEEP as part of a lung protective ventilation strategy seem to be the safest and most effective recruitment manoeuvres. As paediatric physiology is essentially different from adult, paediatric studies are needed to determine the role of recruitment manoeuvres in the PICU.

Mechanical ventilation in acute respiratory failure: recruitment and high positive end-expiratory pressure are necessary

PURPOSE OF REVIEW

To review as best the critical care clinicians can recruit the acute respiratory distress syndrome (ARDS) lungs and keep the lungs opened, assuring homogeneous ventilation, and to present the experimental and clinical results of these mechanical ventilation strategies, along with possible improvements in patient outcome based on selected published medical literature from 1972 to 2004 (highlighting the period from June 2003 to June 2004 and recent results of the authors' group research).

RECENT FINDINGS

In the experimental setting, repeated derecruitments accentuate lung injury during mechanical ventilation, whereas open lung concept strategies can attenuate lung injury. In the clinical setting, recruitment maneuvers improve short-term oxygenation in ARDS patients. A recent prospective clinical trial showed that low versus intermediate positive end-expiratory pressure (PEEP) levels (8 vs 13 cm H2O) associated with low tidal ventilation had the same effect on ARDS patient survival. Nevertheless, both conventional and electrical impedance thoracic tomography studies indicate that stepwise PEEP recruitment maneuvers increase lung volume and the recruitment percentage of lung tissue, and higher levels of PEEP (18-26 cm H2O) are necessary to keep the ARDS lungs opened and assure a more homogeneous low tidal ventilation.

SUMMARY

Stepwise PEEP recruitment maneuvers can open collapsed ARDS lungs. Higher levels of PEEP are necessary to maintain the lungs open and assure homogenous ventilation in ARDS. In the near future, thoracic CT associated with high-performance monitoring of regional ventilation (electrical impedance tomography) may be used at the bedside to determine the optimal mechanical ventilation of ARDS patients.

Bench-to-bedside review: Recruitment and recruiting maneuvers

In patients with acute respiratory distress syndrome (ARDS), the lung comprises areas of aeration and areas of alveolar collapse, the latter producing intrapulmonary shunt and hypoxemia. The currently suggested strategy of ventilation with low lung volumes can aggravate lung collapse and potentially produce lung injury through shear stress at the interface between aerated and collapsed lung, and as a result of repetitive opening and closing of alveoli. An 'open lung strategy' focused on alveolar patency has therefore been recommended. While positive end-expiratory pressure prevents alveolar collapse, recruitment maneuvers can be used to achieve alveolar recruitment. Various recruitment maneuvers exist, including sustained inflation to high pressures, intermittent sighs, and stepwise increases in positive end-expiratory pressure or peak inspiratory pressure. In animal studies, recruitment maneuvers clearly reverse the derecruitment associated with low tidal volume ventilation, improve gas exchange, and reduce lung injury. Data regarding the use of recruitment maneuvers in patients with ARDS show mixed results, with increased efficacy in those with short duration of ARDS, good compliance of the chest wall, and in extrapulmonary ARDS. In this review we discuss the pathophysiologic basis for the use of recruitment maneuvers and recent evidence, as well as the practical application of the technique.