title: Higher levels of spontaneous breathing induce lung recruitment and reduce global stress/strain in experimental lung injury.
abstract: BACKGROUND
  Spontaneous breathing (SB) in the early phase of the acute respiratory distress syndrome is controversial. Biphasic positive airway pressure/airway pressure release ventilation (BIPAP/APRV) is commonly used, but the level of SB necessary to maximize potential beneficial effects is unknown.
  
  
  METHODS
  Experimental acute respiratory distress syndrome was induced by saline lung lavage in anesthetized and mechanically ventilated pigs (n = 12). By using a Latin square and crossover design, animals were ventilated with BIPAP/APRV at four different levels of SB in total minute ventilation (60 min each): (1) 0% (BIPAP/APRV0%); (2) greater than 0 to 30% (BIPAP/APRV>0-30%); (3) greater than 30 to 60% (BIPAP/APRV>30-60%); and (4) greater than 60% (BIPAP/APRV>60%). Gas exchange, hemodynamics, and respiratory variables were measured. Lung aeration was assessed by high-resolution computed tomography. The distribution of perfusion was marked with Ga-labeled microspheres and evaluated by positron emission tomography.
  
  
  RESULTS
  The authors found that higher levels of SB during BIPAP/APRV (1) improved oxygenation; (2) decreased mean transpulmonary pressure (stress) despite increased inspiratory effort; (3) reduced nonaerated lung tissue, with minimal changes in the distribution of perfusion, resulting in decreased low aeration/perfusion zones; and (4) decreased global strain (mean ± SD) (BIPAP/APRV0%: 1.39 ± 0.08; BIPAP/APRV0-30%: 1.33 ± 0.03; BIPAP/APRV30-60%: 1.27 ± 0.06; BIPAP/APRV>60%: 1.25 ± 0.04, P < 0.05 all vs. BIPAP/APRV0%, and BIPAP/APRV>60% vs. BIPAP/APRV0-30%).
  
  
  CONCLUSIONS
  In a saline lung lavage model of experimental acute respiratory distress syndrome in pigs, levels of SB during BIPAP/APRV higher than currently recommended for clinical practice, that is, 10 to 30%, improve oxygenation by increasing aeration in dependent lung zones without relevant redistribution of perfusion. In presence of lung recruitment, higher levels of SB reduce global stress and strain despite an increase in inspiratory effort.
authors.affiliation: From the Pulmonary Engineering Group, Department of Anesthesiology and Intensive Care Medicine, University Hospital Dresden, Technische Universität Dresden, Dresden, Germany (A.G., A.B., N.C., A.B., S.Z., C.U., P.M.S., T.K., and M.G.d.A.); Department of Electric Engineering, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil (A.B.); Institute of Informatics and Biometry, Dresden, Germany (B.W.); Institute of Nuclear Medicine, University Hospital Dresden, Dresden, Germany (G.W., M.A., and J.K.); and IRCCS San Martino Hospital, Department of Surgical Sciences and Integrated Diagnostics, University of Genoa, Genoa, Italy (P.P.).
authors.forename: Andreas
authors.initials: A
authors.lastname: Güldner
authors.forename: Anja
authors.initials: A
authors.lastname: Braune
authors.forename: Nadja
authors.initials: N
authors.lastname: Carvalho
authors.forename: Alessandro
authors.initials: A
authors.lastname: Beda
authors.forename: Stefan
authors.initials: S
authors.lastname: Zeidler
authors.forename: Bärbel
authors.initials: B
authors.lastname: Wiedemann
authors.forename: Gerd
authors.initials: G
authors.lastname: Wunderlich
authors.forename: Michael
authors.initials: M
authors.lastname: Andreeff
authors.forename: Christopher
authors.initials: C
authors.lastname: Uhlig
authors.forename: Peter M
authors.initials: PM
authors.lastname: Spieth
authors.forename: Thea
authors.initials: T
authors.lastname: Koch
authors.forename: Paolo
authors.initials: P
authors.lastname: Pelosi
authors.forename: Jörg
authors.initials: J
authors.lastname: Kotzerke
authors.forename: Marcelo Gama
authors.initials: MG
authors.lastname: de Abreu
mesh_terms: D000818:Animals; D018592:Cross-Over Studies; D004195:Disease Models, Animal; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology; D055370:Lung Injury / Q000503:physiopathology*; D049268:Positron-Emission Tomography / Q000379:methods; D012119:Respiration; D012128:Respiratory Distress Syndrome / Q000503:physiopathology*; D015656:Respiratory Mechanics / Q000502:physiology*; D013552:Swine; D014057:Tomography, X-Ray Computed / Q000379:methods