It is not well understood how different ventilation modes affect the regional distribution of ventilation, particularly within the injured lung.OBJECTIVES
We compared respiratory mechanics, lung aeration and regional specific ventilation (OBJECTIVES
) 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.DESIGN
Randomised experimental study.ANIMALS AND INTERVENTIONS
New 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 MEASURES
Airway 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.RESULTS
Lung 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.CONCLUSION
A 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.