Felipe Saddy Gisele P. Oliveira Cristiane S. N. B. Garcia Liliane M. Nardelli Andreia F. Rzezinski Debora S. Ornellas Marcelo M. Morales Vera L. Capelozzi Paolo Pelosi Patricia R. M. Rocco Assisted ventilation modes reduce the expression of lung inflammatory and fibrogenic mediators in a model of mild acute lung injury Received: 1 October 2009 Accepted: 6 December 2009 Published online: 24 March 2010 Ó Copyright jointly held by Springer and ESICM 2010 Electronic supplementary material The online version of this article (doi:10.1007/s00134-010-1808-6) contains supplementary material, which is available to authorized users. F. Saddy Á G. P. Oliveira Á C. S. N. B. Garcia Á L. M. Nardelli Á A. F. Rzezinski Á D. S. Ornellas Á P. R. M. Rocco ( ) ) Laboratory of Pulmonary Investigation, Carlos Chagas Filho Institute of Biophysics-C.C.S., Federal University of Rio de Janeiro, Rio de Janeiro, Brazil e-mail: prmrocco@biof.ufrj.br Tel.: ?55-2125626530 Fax: ?55-21-22808193 F. Saddy Ventilatory Care Unit Copa D‘Or Hospital, Rio de Janeiro, Brazil F. Saddy Intensive Care Unit Pro Cardiaco Hospital, Rio de Janeiro, Brazil D. S. Ornellas Á M. M. Morales Laboratory of Cellular and Molecular Physiology, Carlos Chagas Filho Institute of Biophysics-C.C.S., Federal University of Rio de Janeiro, Rio de Janeiro, Brazil V. L. Capelozzi Department of Pathology, University of Sa ˜o Paulo, Sa ˜o Paulo, Brazil P. Pelosi Department of Ambient, Health and Safety, University of Insubria, Varese, Italy Abstract Purpose: The goal of the study was to compare the effects of different assisted ventilation modes with pressure controlled ventilation (PCV) on lung histology, arterial blood gases, inflammatory and fibro- genic mediators in experimental acute lung injury (ALI). Methods: Para- quat-induced ALI rats were studied. At 24 h, animals were anaesthetised and further randomized as follows (n = 6/group): (1) pressure controlled ventilation mode (PCV) with tidal volume (V T ) = 6 ml/kg and inspira- tory to expiratory ratio (I:E) = 1:2; (2) three assisted ventilation modes: (a) assist-pressure controlled ventila- tion (APCV1:2) with I:E = 1:2, (b) APCV1:1 with I:E = 1:1; and (c) biphasic positive airway pressure and pressure support ventilation (Bi- Vent ? PSV), and (3) spontaneous breathing without PEEP in air. PCV, APCV1:1, and APCV1:2 were set with P insp = 10 cmH 2 O and PEEP = 5 cmH 2 O. BiVent ? PSV was set with two levels of CPAP [inspiratory pressure (P High = 10 cmH 2 O) and positive end-expiratory pressure (P Low = 5 cmH 2 O)] and inspiratory/ expiratory times: T High = 0.3 s and T Low = 0.3 s. PSV was set as fol- lows: 2 cmH 2 O above P High and 7 cmH 2 O above P Low . All rats were mechanically ventilated in air and PEEP = 5 cmH 2 O for 1 h. Results: Assisted ventilation modes led to better functional improvement and less lung injury compared to PCV. APCV1:1 and BiVent ? PSV pre- sented similar oxygenation levels, which were higher than in APCV1:2. Bivent ? PSV led to less alveolar epithelium injury and lower expres- sion of tumour necrosis factor-a, interleukin-6, and type III procolla- gen. Conclusions: In this experimental ALI model, assisted ventilation modes presented greater beneficial effects on respiratory function and a reduction in lung injury compared to PCV. Among assisted ventilation modes, Bi-Vent ? PSV demonstrated better functional results with less lung damage and expression of inflamma- tory mediators. Keywords Acute lung injury Á Ventilator-associated lung injury Á Cytokines Á Type III procollagen Intensive Care Med (2010) 36:1417–1426 DOI 10.1007/s00134-010-1808-6 EXPERIMENTAL