From the Department of Physics, University of Helsinki (LP, SS), Helsinki University Central Hospital, Helsinki, Finland (LP, SS), Université de Picardie Jules Verne, Inserm U1105 and Paediatric Lung Function Laboratory, CHU Amiens, Amiens, France (SB, LB), Anesthesiological Investigation Unit, University of Geneva, Geneva, Switzerland (IM, GA, CD), Biomedical Beamline-ID17, European Synchrotron Radiation Facility, Grenoble, France (LB), Department of Medical Physics and Informatics, University of Szeged, Szeged, Hungary (FP), Geneva Children's Hospital, University Hospitals of Geneva and Geneva University, Geneva, Switzerland (WH)
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BACKGROUNDIt is not well understood how different ventilation modes affect the regional distribution of ventilation, particularly within the injured lung.OBJECTIVESWe compared respiratory mechanics, lung aeration and regional specific ventilation () distributions in healthy and surfactant-depleted rabbits ventilated with pressure-regulated volume control (PRVC) mode with a decelerating inspiratory flow or with volume control (VC) mode.DESIGNRandomised experimental study.ANIMALS AND INTERVENTIONSNew Zealand white rabbits (n = 8) were anaesthetised, paralysed and mechanically ventilated either with VC or PRVC mode (tidal volume: 7 ml kg−1; rate: 40 min−1; positive end-expiratory pressure (PEEP): 3 cmH2O), at baseline and after lung injury induced by lung lavage.MAIN OUTCOME MEASURESAirway resistance (Raw), respiratory tissue damping (G) and elastance (H) were measured by low-frequency forced oscillations. Synchrotron radiation computed tomography during stable xenon wash-in was used to measure regional lung aeration and specific ventilation and the relative fraction of nonaerated, trapped, normally, poorly and hyperinflated lung regions.RESULTSLung lavage significantly elevated peak inspiratory pressure (PIP) (P < 0.001). PIP was lower on PRVC compared with VC mode (−12.7 ± 1.7%, P < 0.001). No significant differences in respiratory mechanics, regional ventilation distribution, strain or blood oxygenation could be detected between the two ventilation modes.CONCLUSIONA decelerating flow pattern (PRVC) resulted in equivalent regional ventilation distribution, respiratory mechanics and gas exchange, in both normal and mechanically heterogeneous lungs with, however, a significantly lower peak pressure. Our data suggest that the lower PIP on PRVC ventilation was because of the decelerating flow pattern rather than the ventilation distribution.