title: Recruitment maneuvers attenuate repeated derecruitment-associated lung injury.
abstract: OBJECTIVE
  Repeated derecruitments of previously recruited lungs can exacerbate lung injuries during mechanical ventilation. The aim of this study was to assess lung injury associated with repeated derecruitments and to assess whether this type of injury could be attenuated by recruitment maneuvers.
  
  
  METHODS
  Prospective, randomized, experimental animal study.
  
  
  METHODS
  University laboratory.
  
  
  METHODS
  New Zealand White rabbits.
  
  
  METHODS
  Twenty-one rabbits were ventilated in pressure-controlled mode with constant tidal volume (10 mL/kg). After lung injury was induced by repeated saline lavage, positive end-expiratory pressure (PEEP) at a lower inflection point was applied for 3 hrs. The control group (n = 7) received ventilation with the same PEEP for 3 hrs without derecruitments. In the derecruitment group (n = 7), derecruitment was repeatedly induced by intentional disconnection of the ventilatory circuit for 1 min every 10 mins for 3 hrs. In the recruitment maneuver group (n = 7), continuous positive airway pressure of 30 cm H2O was applied for 30 secs after each derecruitment.
  
  
  RESULTS
  After PEEP levels were increased to lower the inflection point value, Pao2 increased to >500 mm Hg in all groups. Increased Pao2 persisted at >450 mm Hg in the control and recruitment maneuver groups, whereas progressive declines in arterial oxygen levels were observed in the derecruitment group (median, 381.1 mm Hg [interquartile range, 350.1-466.7 mm Hg] at 2 hrs and 318.2 mm Hg [214.3-414.9 mm Hg] at 3 hrs, p < .05 compared with other groups). Histologically, there was significantly increased hyaline membrane formation in alveolar ducts in the derecruitment group compared with the control group (p = .005). Also, significantly more membranous and respiratory bronchiolar injuries were observed in the derecruitment group compared with the control and recruitment maneuver group (p < .005).
  
  
  CONCLUSIONS
  These findings suggest that repeated derecruitments could induce lung injuries during mechanical ventilation, and recruitment maneuvers may attenuate derecruitment-associated lung injuries.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Won-Jung
authors.initials: WJ
authors.lastname: Koh
authors.forename: Gee Young
authors.initials: GY
authors.lastname: Suh
authors.forename: Joungho
authors.initials: J
authors.lastname: Han
authors.forename: Shin-Hye
authors.initials: SH
authors.lastname: Lee
authors.forename: Eun Hae
authors.initials: EH
authors.lastname: Kang
authors.forename: Man Pyo
authors.initials: MP
authors.lastname: Chung
authors.forename: Hojoong
authors.initials: H
authors.lastname: Kim
authors.forename: O Jung
authors.initials: OJ
authors.lastname: Kwon
mesh_terms: D000818:Animals; D001794:Blood Pressure; D004195:Disease Models, Animal; D006339:Heart Rate; D008297:Male; D011175:Positive-Pressure Respiration / Q000009:adverse effects / Q000379:methods*; D011659:Pulmonary Gas Exchange; D011817:Rabbits; D012119:Respiration; D012128:Respiratory Distress Syndrome / Q000209:etiology* / Q000473:pathology