title: Pressure safety range of barotrauma with lung recruitment manoeuvres: a randomised experimental study in a healthy animal model.
abstract: BACKGROUND
  Recruitment manoeuvres aim at reversing atelectasis during general anaesthesia but are associated with potential risks such as barotrauma.
  
  
  OBJECTIVE
  To explore the range of pressures that can be used safely to fully recruit the lung without causing barotrauma in an ex-vivo healthy lung rabbit model.
  
  
  METHODS
  Prospective, randomised, experimental study.
  
  
  METHODS
  Experimental Unit, La Paz University Hospital, Madrid, Spain.
  
  
  METHODS
  Fourteen healthy young New Zealand rabbits of 12 weeks of age.
  
  
  METHODS
  Animals were euthanised, the thorax and both pleural spaces were opened and the animals were allocated randomly into one of two groups submitted to two distinct recruitment manoeuvre strategies: PEEP-20 group, in which positive end-expiratory pressure (PEEP) was increased in 5-cmH2O steps from 0 to 20 cmH2O and PEEP-50 group, in which PEEP was increased in 5-cmH2O steps from 0 to 50 cmH2O. In both groups, a driving pressure of 15 cmH2O was maintained until maximal PEEP and its corresponding maximal inspiratory pressures (MIPs) were reached. From there on, driving pressure was progressively increased in 5-cmH2O steps until detectable barotrauma occurred. Two macroscopic conditions were defined: anatomically open lung and barotrauma.
  
  
  METHODS
  We measured open lung and barotrauma MIP, PEEP and driving pressure obtained using each strategy. A pressure safety range, defined as the difference between barotrauma MIP and anatomically open lung MIP, was also determined in both groups.
  
  
  RESULTS
  Open lung MIP was similar in both groups: 23.6 ± 3.8 and 23.3 ± 4.1 cmH2O in the PEEP-50 and PEEP-20 groups, respectively (P = 0.91). However, barotrauma MIP in the PEEP-50 group was higher (65.7 ± 3.4 cmH2O) than in the PEEP-20 group (56.7 ± 5 0.2 cmH2O) (P = 0.003) resulting in a safety range of pressures of respectively 33.3 ± 8.7 and 42.1 ± 3.9 cmH2O (P = 0.035).
  
  
  CONCLUSIONS
  In this ex-vivo model, we found a substantial difference between recruitment and barotrauma pressures using both recruitment strategies. However, a higher margin of safety was obtained when a higher PEEP and lower driving pressure strategy was used for recruiting the lung.
authors.affiliation: Anaesthesiology and Critical Care Department, Puerta de Hierro University Hospital, Madrid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: García-Fernández
authors.forename: Susana
authors.initials: S
authors.lastname: Canfrán
authors.forename: Ignacio A Gómez
authors.initials: IA
authors.lastname: de Segura
authors.forename: Fernando
authors.initials: F
authors.lastname: Suarez-Sipmann
authors.forename: Delia
authors.initials: D
authors.lastname: Aguado
authors.forename: Göran
authors.initials: G
authors.lastname: Hedenstierna
mesh_terms: D000818:Animals; D001469:Barotrauma / Q000628:therapy*; D005260:Female; D023421:Models, Animal; D011175:Positive-Pressure Respiration; D011312:Pressure; D011446:Prospective Studies; D001261:Pulmonary Atelectasis / Q000517:prevention & control*; D011817:Rabbits