Development and application of a double‐piston configured, total‐liquid ventilatory support device

Objective: Perfluorocarbon liquid ventilation has been shown to enhance pulmonary mechanics and gas exchange in the setting of respiratory failure. To optimize the total liquid ventilation process, we developed a volume‐limited, time‐cycled liquid ventilatory support, consisting of an electrically actuated, microprocessor‐controlled, double‐cylinder, piston pump with two separate limbs for active inspiration and expiration. Design: Prospective, controlled, animal laboratory study, involving sequential application of conventional gas ventilation, partial ventilation (PLV), and total liquid ventilation (TLV). Setting: Research facility at a university medical center. Subjects: A total of 12 normal adult New Zealand rabbits weighing 3.25 ± 0.1 kg. Interventions: Anesthestized rabbits were supported with gas ventilation for 30 mins (respiratory rate, 20 cycles/min; peak inspiratory pressure, 15 cm H2O; end‐expiratory pressure, 5 cm H2O), then PLV was established with perflubron (12 mL/kg). After 15 mins, TLV was instituted (tidal volume, 18 mL/kg; respiratory rate, 7 cycles/min; inspiratory/expiratory ratio, 1:2 cycles/min). After 4 hrs of TLV, PLV was re‐established. Measurements and Main Results: Of 12 animals, nine survived the 4‐hr TLV period. During TLV, mean values ± SEM were as follows: PaO2, 363 ± 30 torr; PaCO2, 39 ± 1.5 torr; pH, 7.39 ± 0.01; static peak inspiratory pressure, 13.2 ± 0.2 cm H2O; static end‐expiratory pressure, 5.5 ± 0.1 cm H2O. No significant changes were observed. When compared with gas ventilation and PLV, significant increases occurred in mean arterial pressure (62.4 ± 3.5 torr vs. 74.0 ± 1.2 torr) and central venous pressure (5.6 ± 0.7 cm H2O vs. 7.8 ± 0.2 cm H2O) (p < .05). Conclusions: Total liquid ventilation can be performed successfully utilizing piston pumps with active expiration. Considering the enhanced flow profiles, this device configuration provides advantages over others.