title: A perfluorochemical loss/restoration (L/R) system for tidal liquid ventilation.
abstract: Tidal liquid ventilation is the transport of dissolved respiratory gases via volume exchange of perfluorochemical (PFC) liquid to and from the PFC-filled lung. All gas-liquid surface tension is eliminated, increasing compliance and providing lung protection due to lower inflation pressures. Tidal liquid ventilation is achieved by cycling fluid from a reservoir to and from the lung by a ventilator. Current approaches are microprocessor-based with feedback control. During inspiration, warmed oxygenated PFC liquid is pumped from a fluid reservoir/gas exchanger into the lung. PFC fluid is conserved by condensing (60-80% efficiency) vapor in the expired gas. A feedback-control system was developed to automatically replace PFC lost due to condenser inefficiency. This loss/restoration (L/R) system consists of a PFC-vapor thermal detector (+/- 2.5%), pneumatics, amplifiers, a gas flow detector (+/- 1%), a PFC pump (+/- 5%), and a controller. Gravimetric studies of perflubron loss from a flask due to evaporation were compared with experimental L/R results and found to be within +/- 1.4%. In addition, when L/R studies were conducted with a previously reported liquid ventilation system over a four-hour period, the L/R system maintained system perflubron volume to within +/- 1% of prime volume and 11.5% of replacement volume, and the difference between experimental PFC loss and that of the L/R system was 1.8 mL/hr. These studies suggest that the PFC L/R system may have significant economic (appropriate dosing for PFC loss) as well as physiologic (maintenance of PFC inventory in the lungs and liquid ventilator) impact on liquid ventilation procedures.
authors.affiliation: Drexel University School of Biomedical Engineering Science and Health Systems, Philadelphia, Pennsylvania, USA. rlibros@ccp.cc.pa.us
authors.forename: R
authors.initials: R
authors.lastname: Libros
authors.forename: C M
authors.initials: CM
authors.lastname: Philips
authors.forename: M R
authors.initials: MR
authors.lastname: Wolfson
authors.forename: T H
authors.initials: TH
authors.lastname: Shaffer
mesh_terms: D002138:Calibration; D004867:Equipment Design; D005466:Fluorocarbons / Q000032:analysis*; D021061:Liquid Ventilation / Q000295:instrumentation*
chemical_list: D005466:Fluorocarbons