Objective: To study the effect of a sustained inflation (SI) maneuver on the regional distribution of gas and perfluorocarbon (PFC) during partial liquid ventilation (PLV) in normal pigs using computerized densitometry.
Study design: Observational study.
Setting: Animal research laboratory.
Participants: Three healthy anaesthetized pigs.
Interventions: Partial liquid ventilation, lung recruitment, CT densitometry.
Methodology: Lungs were filled with PFC to "liquid functional residual capacity (FRC)" (35-41 ml/kg) and CT images were recorded at a series of predetermined airway pressure levels (0, 20, 30, 40 cm H2O) both before and after SI to an airway pressure of 40 cm H2O for 30 sec. Anterior, middle, and posterior regions from upper (apical lung) to lower (basal lung) CT slices were analyzed at each pressure level for Hounsfield units to describe the relative distribution of gas and PFC before and after SI. Using an occlusion technique true gas volume above FRC was determined at each pressure level, before and after SI, and a pressure-volume (gas) envelope determined for each animal.
Results: At low airway pressures (<20 cm H2O) gas was distributed predominantly to the anterior (non-dependent) part of the lung and PFC predominantly to the posterior (dependent) lung. Gas and liquid were more uniformly distributed throughout the lung at airway pressures >20 cm H2O. Generation of a pressure-volume (gas) envelope for each animal demonstrated an increase in total gas volume above FRC at each pressure level following recruitment of the lung with SI. However, marked regional differences were evident with the greatest effects of SI seen at higher airway pressures in posterior and basal regions.
Conclusion: The healthy PFC filled lung demonstrates an increase in total gas volume following SI. CT densitometry suggests marked heterogeneity of gas/PFC distribution between different regions of lung and heterogeneity of response to SI.
2007 Wiley-Liss, Inc.