Effects of paralysis on lung mechanics and gas exchange during partial liquid ventilation

We hypothesized that paralysis during partial liquid ventilation (PLV) would not alter oxygenation due to the stabilizing effect PLV has on end-expiratory lung volume (EELV). We studied 8 newborn piglets (1.16±0.22 kg) with saline lavage-induced lung injury (PO2<80 torr, >30% reduction in compliance). Ventilator parameters included the following: FIO2 of 1.0; assist/control back-up rate of 30 breaths/min; positive end-expiratory pressure of 4 cm H2O; peak inspiratory pressure to achieve 15 mL/kg tidal volume; inspiratory time adequate for end-expiratory flow to return to zero. Perflubron (LiquiVent™) was administered until a meniscus was visible in the endotracheal tube. Measurements of compliance (Cdyn), resistance (Raw), minute ventilation (V_E), change in end-expiratory lung volume (ΔEELV), arterial/alveolar oxygen ratio (a/A), oxygenation index (OI), and mean and peak airway pressures (MAP, PIP) were recorded for one hour before and after paralysis under conditions of matched ventilatory support. Rate during paralysis was set as the mean spontaneous respiratory rate during spontaneous breathing. Data analysis used paired t-tests with significance set at p<0.05. PLV PLV-paralysis p value a/A 0.23±0.10 0.22±0.12 NS OI 10.9±6.9 13.2±9.2 NS V_E (L/kg/min) 1.37±0.31 1.39±0.31 NS Cdyn (mL/cmH₂0/kg) 1.00±0.16 1.04±0.46 NS PIP (cmH₂0) 30±1 34±2 0.01 Raw (cmH₂0/L/s) 152±11 195±11 0.003 ΔEELV (mL/kg) - -6.35±6.3 0.03 Conclusions: In this model, paralysis during PLV leads to increased Raw and decreased end expiratory lung volume without hemodynamic compromise or changes in oxygenation. Increased PIP is needed to maintain V_E. (LiquiVent™ provided by Alliance Pharmaceutical Corp.).