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Previous Volume 336:660 February 27, 1997 Number 9 Next

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To the Editor: Leach et al. report (Sept. 12 issue)¹ that partial liquid ventilation with perfluorocarbons in premature infants may be an effective therapy for severe respiratory distress syndrome. Their conclusion that such treatment prevented oxygen toxicity, reduced the incidence of barotrauma due to improved dynamic compliance, and improved ventilation — each of which is a highly desirable goal of therapy in neonates with this often fatal syndrome — may not be supported by the results.

Each neonate was reintubated at entry into the study, but the authors do not mention the size of the new tube and whether retained occlusive secretions were present. Improved air flow from either an unobstructed or enlarged lumen could have accounted for the increase in dynamic compliance as well as the improved ventilation.

More important is the issue of improved oxygenation. To the clinician, perhaps the measure of oxygenation that best guides the tapering of potentially toxic levels of inspired oxygen is the arterial oxygen content. This value is dependent on the percentage of oxygen saturation of hemoglobin, which accounts for nearly 99 percent of the oxygen carriage in blood. The reader cannot determine the effect of partial liquid ventilation on the percentage of oxygen saturation of hemoglobin despite the fact that this value is usually reported with the partial pressure of arterial oxygen during blood gas analysis. One would hope the improvement in oxygenation was as beneficial as the improvements in compliance and ventilation.

Jeffrey E. Salon, M.D.
1240 Westhill Dr.
Columbus, OH 43213-2623

References

1. Leach CL, Greenspan JS, Rubenstein SD, et al. Partial liquid ventilation with perflubron in premature infants with severe respiratory distress syndrome. N Engl J Med 1996;335:761-767. [Free Full Text]

To the Editor: We appreciate the opportunity to clarify several points. The patients were reintubated with the same-size endotracheal tube, and it was after this that base-line values for gas exchange and lung mechanics were obtained. The protocol was designed to permit direct comparison of pulmonary function during gas ventilation with that during partial liquid ventilation.

Oxygen saturation is one indicator of oxygenation. The ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen has also been used as an indicator of the severity of lung dysfunction. We chose to report data on the partial pressure of arterial oxygen and fraction of inspired oxygen to enable the reader to assess lung function using that ratio. Moreover, the success of this intervention can be gauged by the ability of the investigators to reduce the level of supplemental oxygen from 100 percent to less than 60 percent while documenting improved partial pressure of arterial oxygen at the same time.

Our disclosure statement should have stated that Drs. Fuhrman, Shaffer, and Wolfson are inventors; patents related to their inventions, filed by several universities, are currently licensed by Alliance Pharmaceutical Corporation, which manufactures LiquiVent, the perflubron used in our study.

Corinne L. Leach, M.D., Ph.D.
Bradley P. Fuhrman, M.D.
Children's Hospital of Buffalo
Buffalo, NY 14222

Thomas H. Shaffer, Ph.D.
Temple University
Philadelphia, PA 19140

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