© 2006 American Thoracic Society
Why Partial Liquid Ventilation Did Not Fulfill Its PromiseFrom the Authors:We thank Drs. Degraeuwe and Zimmermann for their interest and comments regarding our recent article on partial liquid ventilation (PLV) (1). We agree with their view on the need to publish negative trials, but we disagree with their position that PLV was too hastily extrapolated from total liquid ventilation (TLV) and that our study design was poor. As Drs. Degraeuwe and Zimmermann indicate, dozens of animal studies using PLV were published before we began our trial, and to the best of our knowledge TLV has never been used in humans. In addition, almost 200 patients in published and unpublished reports received PLV before the start of the study (2, 3).
Our study was begun in 1998 and designed the year before—preceding all of the lung-protective ventilation randomized controlled trials (RCTs). Our study design took into account the animal and human data available at the time, including encouraging subgroup data from a phase II trial (3), which created enthusiasm for performing the study we performed. Although our patients were generally younger, the mortality of patients in all three of our groups (15 to 26%) was equivalent to or lower than those observed in a number of lung protective ventilation RCTs (4–6), especially when one considers the fact that our patients had more severe lung dysfunction than the majority of patients in these trials. This is particularly true of the ARDSnet studies (4, 5), which only required a PaO2/FIO2 < 300 regardless of positive end-expiratory pressure (PEEP) and FIO2 for enrollment. Our patients required an initial PaO2/FIO2 < 200 mm Hg. After meeting this oxygenation criterion, all patients had to have a PaO2/FIO2 < 300 mm Hg on a PEEP PLV or TLV may not be the most efficacious way of providing perfluorocarbon-assisted ventilation. The use of a single small dose (< 5 ml/kg) to facilitate initial lung recruitment or aerosolized or vaporized perfluorocarbon may result in better patient outcomes. However, data regarding these approaches were not available at the time of our study design (1997). Although we believe PLV as performed in our study does not have a future, we do feel that research in perfluorocarbon-assisted ventilation should continue.
Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada FOOTNOTES Conflict of Interest Statement: R.M.K. received a $65,000 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 in the field of mechanical ventilation (> $10,000/yr, but < $50,000/yr). He chaired a DSMB for Leo Pharma in relation to a surfactant trial (> $ 10,000/yr and < $50,000/yr). He was on the Alliance Advisory Board for the trial presented in this publication, but received no financial compensation for this. REFERENCES
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13 cm H2O and FIO2