PRESSURE-CYCLED VERSUS VOLUME-CYCLED VENTILATION IN LIQUID-VENTILATEDNEONATAL PIGLET LUNGS

Background/Purpose: If the goal of partial liquid ventilation (PLV) wi th perfluorocarbons in the management of respiratory failure is to imp rove dynamic lung compliance (C-dyn) and pulmonary vascular resistance (PVR) while sustaining O-2 delivery, the optimal ventilatory manageme nt is unclear. The authors asked if volume-cycled or pressure-limited ventilation had different effects on PVR, cardiac index (CI), and C-dy n in uninjured and injured neonatal piglet lungs. Methods: Anesthetize d piglets (6 to 8 kg) were ventilated after tracheostomy. C-dyn was me asured by in-line Fleisch pneumotach/PC data acquisition terminal. The rmodilution instrumentation allowed determination of both CI and PVR. Volume-control or pressure-limited ventilation was established in unin jured or injured (surfactant deficiency induced by saline ravage at 18 mL/kg) animals. After a stable 30-minute baseline, animals were assig ned randomly to one of four groups: group I (n = 9), uninjured animals plus volume-cycled ventilation (intermittent mandatory ventilation [I MV], 10 bpm; tidal volume [TV], 15 mL/kg, positive end-expiratory pres sure [PEEP], 5 cm H2O; FIO2, 1.0; and PLV for 150 minutes); group II ( n = 9), uninjured animals plus pressure-limited ventilation (IMV, 10 b pm; peak inspiratory pressure (PIP), 25 cm H2O, PEEP, 5 cm H2O, FIO2 1 .0; and PLV for 150 minutes); group III (n = 7), injured animals plus volume-cycled ventilation (IMV, 10 bpm; TV, 15 mL/kg; PEEP, 5 cm H2O; FIO2, 1.0 for 30 minutes, followed by saline injury for 30 minutes, fo llowed by PLV rescue for 120 minutes); group IV (n = 7), injured anima ls plus pressure-limited ventilation (IMV, 10 bpm; PIP, 25 cm H2O; PEE P, 5 cm H2O; FIO2, 1.0 for 30 minutes, followed by saline injury, and PLV rescue). Comparison within and between groups was accomplished by repeated measures analysis of variance (ANOVA) with Tukey correction. Results: There was no significant difference between volume-cycled or pressure-limited ventilation in healthy lungs; however, in the setting of lung injury, dynamic compliance was 1.44 +/- 0.15 after 180 minute s in the volume-cycled group and 0.91 +/- 0.10 in the pressure-limited group after the same interval (mL/cm H2O - kg +/- SEM). Similarly, PV R was 100 +/- 6 in the volume-cycled group and 145 +/- 12 in the press ure-limited group after 180 minutes of lung injury (mm Hg/L/ kg . min +/- SEM). Cardiac index declined significantly in all groups independe nt of ventilatory mode. Conclusions: These results suggest that in the setting of lung injury, C-dyn and PVR improved significantly when vol ume-cycled, compared with pressure-limited ventilation was used. Altho ugh no difference existed between ventilatory modes in healthy lungs, pressure-limited ventilation, when combined with PLV in injured lungs, had adverse effects on lung compliance and pulmonary vascular resista nce. Volume-cycled ventilation may optimize the ability of perfluoroca rbon to recruit collapsed or atelectatic lung regions. J Pediatr Surg 33:1158-1162. Copyright (C) 7998 by W.B. Saunders Company.