Synchronized gas and partial liquid ventilation in lung-injured animals: Improved gas exchange with decreased effort

We hypothesized that partial liquid ventilation (PLV) with perflubron in sp ontaneously breathing lung-injured animals would increase respiratory workl oad compared to animals treated with gas Ventilation (GV), and that a fully synchronized mode, assist-control ventilation (AC), would reduce the pigle ts' effort when compared to intermittent mandatory ventilation (IMV) or syn chronized IMV (SIMV) during both GV and PLV. Newborn piglets with saline la vage-induced lung injury were randomized to sequential 30-min periods of IM V --> SIMV --> AC (n = 5), or AC --> SIMV --> IMV (n = 5) during GV followe d by PLV. Pulmonary mechanics measurements and an esophageal patient effort index (PEI, defined as the product of the area below baseline of the esoph ageal pressure-time curve and respiratory rate [RR]) were determined to est imate the patient's nonmechanical work of breathing, using a computer-assis ted lung mechanics analyzer. GV to PLV comparisons showed no change in PEI (IMV, 57.8 vs. 49.7; SIMV, 52 .3 vs. 46.8; AC, 15.7 vs. 13.7 cm H2O . s/min); intermode comparisons showe d significantly decreased PEI in AC vs. IMV and SIMV during GV, and in AC v s. SIMV (AC vs. IMV, P = 0.06) during PLV. AC consistently resulted in the highest minute ventilation, lowest total respiratory rate, most physiologic pH, and least tidal volume variability. These observations suggest that synchronization with AC during GV and PLV m ay have substantial physiologic benefits. (C) 1999 Wiley-Liss, Inc.