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Acute respiratory distress syndrome CARDS) is a general term used for severe acute respiratory failure or parenchymal lung damage, which occurs progressively and has a diverse etiology. ARDS is characterized by a ratio of Pao2 to fraction of inspired oxygen (FIo2) of less than 200, evidence on chest radiographs of bilateral infiltrates, and pulmonary artery capillary pressure of 18 mm Hg or less.'2 In the United States, approximately 250000 to 400000 cases of ARDS are reported annually.' Despite numerous advances in healthcare and technology, mortality due to ARDS has remained relatively constant at 40% to 60% since 1967.2 Management of ARDS remains primarily supportive because currently no specific therapy is available.1-4
Submerged survival-another term for liquid ventilation or gas exchange via an artificial liquid medium-has been of major interest to many researchers for more than 3 decades. The liquid media and methods have been improved since Kylstra and his colleagues initially experimented with hyperbarically oxygenated salt solutions in the early 1960s. Kylstra et als discovered that liquid ventilation under controlled environments resulted in few adverse sequelae. However, the methods used to resuscitate subjects treated with liquid ventilation and administration techniques warrant further study.
Currently, the liquid medium most favored by researchers is a member of the family of fluorocarbons first synthetically produced as part of the Manhattan Project during World War II. Formerly, liquid perfluorochemicals were developed and used as inert media for harvesting uranium isomers used in the atomic bomb.
Perflubron (LiquiVent, Alliance Pharmaceutical Corp, San Diego, Calif), a liquid perfluorochemical, fulfilled the requirements for a medium with favorable medicinal properties for treating acute lung injury and ARDS. Perflubron looks like crystal-clear spring water and is odorless and colorless. However, it has an oily texture, is twice as dense (1.9 g/mL) as water, and evaporates more quickly than water does (vapor pressure = 11 mm Hg at 37degC).
Unlike the situation with the salt solutions used by Kylstra et al, at atmospheric pressures, oxygen and carbon dioxide are highly soluble in perflubron.8 Treatment with perflubron is similar to, but more physiologically effective than, positive end-expiratory pressure (PEEP). Perflubron reaches and reinflates areas of atelectasis and consolidation, which are commonly in the dependent regions of the lungs.9 In clinical trials, the PEEP-like effect of...