Effects of two stepwise lung recruitment strategies on respiratory function and haemodynamics in anaesthetised pigs: A randomised crossover study.

BackgroundLung recruitment manoeuvres and positive end-expiratory pressure (PEEP) can improve lung function during general anaesthesia. Different recruitment manoeuvre strategies have been described in large international trials: in the protective ventilation using high vs. low PEEP (PROVHILO) strategy, tidal volume (VT) was increased during volume-controlled ventilation; in the individualised peri-operative open-lung approach vs. standard protective ventilation in abdominal surgery (iPROVE) strategy, PEEP was increased during pressure-controlled ventilation.ObjectivesTo compare the effects of the PROVHILO strategy and the iPROVE strategy on respiratory and haemodynamic variables.DesignRandomised crossover study.SettingUniversity hospital research facility.AnimalsA total of 20 juvenile anaesthetised pigs.InterventionsAnimals were assigned randomly to one of two sequences: PROVHILO strategy followed by iPROVE strategy or vice-versa (n = 10/sequence). In the PROVHILO strategy, VT was increased stepwise by 4 ml kg-1 at a fixed PEEP of 12 cmH2O until a plateau pressure of 30 to 35 cmH2O was reached. In the iPROVE strategy, at fixed driving pressure of 20 cmH2O, PEEP was increased up to 20 cmH2O followed by PEEP titration according to the lowest elastance of the respiratory system (ERS).Main outcome measuresWe assessed regional transpulmonary pressure (Ptrans), respiratory system mechanics, gas exchange and haemodynamics, as well as the centre of ventilation (CoV) by electrical impedance tomography.ResultsDuring recruitment manoeuvres with the PROVHILO strategy compared with the iPROV strategy, dorsal Ptrans was lower at end-inspiration (16.3 ± 2.7 vs. 18.6 ± 3.1 cmH2O, P = 0.001) and end-expiration (4.8 ± 2.6 vs. 8.8 ± 3.4 cmH2O, P  ConclusionIn anaesthetised pigs, the iPROVE strategy compared with the PROVHILO strategy increased dorsal Ptrans at the cost of lower MAP during recruitment manoeuvres, and decreased ERS thereafter, without consistent improvement of oxygenation or shift of the CoV.Trial registrationThis study was registered and approved by the Landesdirektion Dresden, Germany (DD24-5131/338/28).