© 2006 American Thoracic Society
Pressure Increase Due to Hydrostatic Pressure of PerfluorocarbonFrom the Authors:We thank Roemer and colleagues for their interest and comments with respect to our recent publication (1) on partial liquid ventilation (PLV). Although we agree with their estimate of the hydrostatic pressure when the airway pressure is zero and the lung filled to the level of the carina with perflubron, we must disagree with their estimates when airway pressures are greater than zero.
Once positive airway pressure is applied, the perflubron moves distally and peripherally in the lung. In many patients, advancing a suction catheter into the airway and suctioning when PEEP One must also keep in mind that the mortality of the PLV group filled to FRC trended lower than the group in which perflubron was added to 1/2 FRC (19% versus 26%). If the analysis by Roemer and coworkers was correct, lung injury and mortality should have been greater with the FRC fill than the 1/2 FRC fill. Of course, we do not know whether another ventilatory strategy for the perflubron group would have changed the results, but the approach we used to provide PLV was based on the results of numerous animal studies demonstrating benefit from PLV (2–4), and the subgroup analysis of a phase II PLV trial (5). There are still many questions surrounding the general issue of perfluorocarbon-assisted ventilation; however, our data demonstrate that PLV is unlikely to be of benefit in the management of ARDS.
Massachusetts General Hospital, Boston, Massachusetts
University of Toronto, Toronto, Ontario, Canada FOOTNOTES Conflict of Interest Statement: R.M.K. received a $65,000 research grant from Alliance Pharmaceuticals in 1999 to support studies of partial liquid ventilation in animal models. A.S.S. has been a paid consultant to Maquet (> $10k/yr) in the field of mechanical ventilation, and chaired a DSMB for Leo Pharma in relation to a surfactant trial (> $10k/yr). REFERENCES
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13 cm H2O yielded no perflubron, even though perflubron could be easily suctioned from the level of the carina or the pharynx prior to applying PEEP. This impact of positive pressure on the peripheral distribution of the perflubron is even more pronounced at end-inspiration, and the peripheral distribution of perflubron with positive pressure can be easily visualized in an animal model with an exposed lung. Thus, it is incorrect to simply add the impact of a static column of fluid exposed to atmospheric pressure to the dynamic pressure applied during PLV. Unfortunately, we are unaware of any data that would allow us to quantify the actual alveolar pressure during PLV.