Recruitment maneuvers in acute respiratory distress syndrome: The safe way is the best way

Table 1 Recruitment maneuver methods and outcomes reported in the literature about clinical studies

Ref.	Population	Design	Interventions	Comparison	Outcome
Pelosi et al[17]	Patients with pulmonary and extrapulmonary ARDS	Observational study	3 sighs/min at Pplat 45 cm H2O, VT to maintain Pplat ≤ 35 cm H2O. PEEP level to keep the lung open	(1) 1 h of ventilator strategy; (2) 2 h of ventilator strategy; and (3) 1 h of ventilator strategy with three consecutive sighs/min at Plat 45 cm H2O	Sigh during protective ventilation improved lung recruitment
Borges et al[44]	Patients with early ARDS	Observational study	Stepwise maximum-recruitment strategy with sequential increments in Paw, in 5-cm H2O steps, until the detection of PaO2 + PaCO2 = 400 mmHg	No comparisons	Stepwise maximum recruitment reverted hypoxemia and fully recruited the lungs
Meade et al[29]	Patients with ARDS (PaO2/FiO2 ≤ 250 mmHg)	Randomized controlled trial	Low VT, Pplat ≤ 30 cm H2O or ≥ 40 cm H2O, and lower or higher PEEP levels according to PEEP/FiO2 table	(1) Ventilator strategy with Pplat ≤ 30 cm H2O, and conventional PEEP levels; (2) “open lung” approach with Pplat ≤ 40 cm H2O, RM, and higher PEEP levels	“Open-lung” approach improved oxygenation associated with lower use of rescue therapies
Hodgson et al[25]	Patients with early ARDS	Observational study	Staircase RM, Paw set to 15 cm H2O above the PEEP, which was increased in a stepwise manner to 20, 30 and then 40 cm H2O every 2 min, followed by PEEP titration	No comparisons	80% of early ARDS patients responded to staircase RM
Hodgson et al[27]	Patients with ARDS	Randomized controlled trial	Control ventilation strategy compared to staircase recruitment maneuver	(1) Control group: PCV, Pplat < 30 cm H2O, VT < 6 mL/kg. FiO2 adjusted to SaO2: 90% to 92%; and (2) Staircase RM: Paw adjusted to 15 cm H2O above PEEP level, which was increased in a stepwise manner to 20, 30 and 40 cm H2O every 2 min, and then reduced in steps of 2.5 from 25 to 15 cm H2O every 3 min until a decrease in SaO2≥ 1%	Staircase RM improved plasma cytokines, oxygenation and lung function over 7 d
Morán et al[26]	Patients with early ARDS	Observational study	Stepwise RM started from plateau pressure/PEEP of 40/25 cm H2O, 5 cm H2O of PEEP was sequentially increased until PaO2/FiO2 of 350 mmHg or plateau pressure/PEEP of 60/40 cm H2O	No comparisons	Stepwise RM improved oxygenation but caused hemodynamic instability and transient hypoxemia

Summary of the results of clinical and experimental studies comparing different recruitment maneuver (RM) methods, according to population, intervention, comparison, outcome criteria. ARDS: Acute respiratory distress syndrome; FiO₂: Inspiratory oxygen fraction; PaO₂: Arterial oxygen partial pressure; PaCO₂: Arterial carbon dioxide partial pressure; PCV: Pressure-controlled ventilation; PEEP: Positive end-expiratory pressure; Pplat: Plateau pressure; SaO₂: Arterial oxygen saturation; V_T: Tidal volume.

Table 2 Recruitment maneuver methods and outcomes reported in the literature about experimental studies

Ref.	Population	Design	Interventions	Comparison	Outcome
Rzezinski et al[23]	Animals with mild extrapulmonary lung injury	Randomized experimental study	Prolonged RM stepwise increase in PIP of 15-20-25 cm H2O above a PEEP of 15 cm H2O (maximal PIP = 40 cm H2O)	(1) Animals ventilated with VT = 6 mL/kg and PEEP = 5 cm H2O with no RMs; (2) Sustained inflation (40 cm H2O for 40 s); or (3) Stepwise increase in Paw of 15, 20, 25 cm H2O above a PEEP of 15 cm H2O (maximal PIP = 40 cm H2O), with interposed periods of Paw = 10 cm H2O above a PEEP = 15 cm H2O	Prolonged RM improved lung function, with less damage to alveolar epithelium, resulting in reduced pulmonary injury
Steimback et al[18]	Animals with extrapulmonary lung injury	Randomized experimental study	Sigh with different PIP and frequencies	(1) Animals ventilated with VT = 6 mL/kg and PEEP = 5 cm H2O with no RMs; (2) Sustained inflation (40 cm H2O for 40 s); (3) RM (180 sighs/h) and PIP (40 cm H2O) (S180/40); (4) RM (10 sighs/h) and PIP (40 cm H2O) (S10/40); and (5) RM (10 sighs/h) and PIP (20 cm H2O) (S10/20)	The reduction in sigh frequency led to a protective effect on the lung and distal organs
Silva et al[8]	Animals with pulmonary and extrapulmonary lung injury	Randomized experimental study	Stepwise RM (5 cm H2O/step, 8.5 s at each step during 51 s); Stepwise RM (5 cm H2O/step, 5 s at each step during 30 s)	(1) Sustained inflation (30 cm H2O for 30 s; (2) Stepwise PIP increase 30 cm H2O over 51 s (STEP-51); and (3) Stepwise PIP increase over 30 s with maximum PIP sustained for a further 30 s (STEP-30/30)	Stepwise RM prevented fibrogenesis and endothelial cell damage

Summary of the results of clinical and experimental studies comparing different recruitment maneuver (RM) methods, according to population, intervention, comparison, outcome criteria. PEEP: Positive end-expiratory pressure; PIP: Peak inspiratory pressure; V_T: Tidal volume.