A functional total liquid ventilator should be simple in design to minimize operating errors and have a low priming volume to minimize the amount of perfluorocarbon needed. Closed system circuits using a membrane oxygenator have partially met these requirements but have high resistance to perfluorocarbon flow and high priming volume. To further this goal, a single piston prototype ventilator with a low priming volume and a new high-efficiency hollow-fiber oxygenator in a circuit with a check valve flow control system was developed.
Prospective, controlled animal laboratory study.
Research facility at a university medical center.
Seven anesthetized, paralyzed, normal New Zealand rabbits
The prototype oxygenator, consisting of cross-wound silicone hollow fibers with a surface area of 1.5 m2 with a priming volume of 190 mL, was tested in a bench-top model followed by an in vivo rabbit model. Total liquid ventilation was performed for 3 hrs with 20 mL·kg−1 initial fill volume, 17.5–20 mL·kg−1 tidal volume, respiratory rate of 5 breaths/min, inspiratory/expiratory ratio 1:2, and countercurrent sweep gas of 100% oxygen.
Bench top experiments demonstrated 66–81% elimination of Co2 and 0.64–0.76 mL·min−1 loss of perfluorocarbon across the fibers. No significant changes in Paco2 and Pao2 were observed. Dynamic airway pressures were in a safe range in which ventilator lung injury or airway closure was unlikely (3.6 ± 0.5 and −7.8 ± 0.3 cm H2O, respectively, for mean peak inspiratory pressure and mean end expiratory pressure). No leakage of perfluorocarbon was noted in the new silicone fiber gas exchange device. Estimated in vivo perfluorocarbon loss from the device was 1.2 mL·min−1.
These data demonstrate the ability of this novel single-piston, nonporous hollow silicone fiber oxygenator to adequately support gas exchange, allowing successful performance of total liquid ventilation.
From the Department of Surgery (ST, EK, DOB, RHB, RBH) and Biomedical Engineering Department (JLB), University of Michigan, Ann Arbor, MI; and the Department of Electronic and Computer Engineering (AF), Tokyo Denki University, Hatoyama, Japan.
Support, in part, by grant R01 HL64373 from the National Institutes of Health.