Effect of single versus multiple dosing on perfluorochemical distribution and elimination during partial liquid ventilation

The objective of this study was to quantitate perfluorochemical (PFC) elimi nation kinetics during partial liquid ventilation (PLV) following an initia l fill with or without hourly dosing. Young New Zealand rabbits were studie d in two groups: Gr I (n = 6), PLV with a single dose of PFC liquid (perflu bron: LiquiVent(R), Alliance Pharmaceutical corp.); and Gr II (n = 5), PLV with PFC liquid and multiple hourly dosing. All rabbits were studied for 4 h, following initial instillation of a volume of PFC liquid equal to the me asured gas functional residual capacity. Animals were ventilated at a const ant breathing frequency (30 br/min), tidal volume (9.3 +/- 0.3 SE mL/kg), p ositive end expiratory pressure (4 cm H2O), and inspiratory time (0.30 s). PFC saturation of mixed expired gas (PFC-Sat) was assessed with a thermal c onductivity analyzer, and PFC elimination was calculated from PFC-Sat, minu te ventilation, and temperature of the expired gas. In GR II, PFC was suppl emented hourly at a volume determined by PFC elimination calculations. The results demonstrated a decrease in PFC-sat and PFC loss with time, inde pendent of group (P < 0.05). In addition, with hourly supplementation (GR I I), PFC-Sat and PFC elimination over time was significantly (P < 0.05) grea ter than in animals (GR i) which did not receive additional doses. These da ta demonstrate that the PFC elimination rate is not constant and is related to the amount of PFC in the respiratory system. This may have occurred due to distributional differences of ventilation and PFC liquid between the si ngle and multiple dosing groups. These findings also suggest that evaluatio n of PFC concentrations in expired gas may be a clinically useful index of intrapulmonary PFC distribution during PLV, and that maintained elevation o f expired gas PFC saturation may guide optimal PFC dosing intervals and dis tribution to maximize protection against barotrauma. Pediatr Pulmonol, 1999 ; 27:410-418. (C) 1999 Wiley-Liss, Inc.