Role of ventilation strategy on perfluorochemical evaporation from the lungs

To study the effect of ventilation strategy on perfluorochemical (PFC) elimination profile (evaporative loss profile; EL), 6 ml/kg of perflubron were instilled into anesthetized normal rabbits. The strategy was to maintain minute ventilation (Ve, in ml/min) in three groups: VeL (low-range Ve, 208 ± 2), VeM (midrange Ve, 250 ± 9), and VeH (high-range Ve, 293 ± 1) over 4 h. In three other groups, respiratory rate (RR, breaths/min) was controlled at 20, 30, or 50 with a constant Ve and adjusted tidal volume. PFC content in the expired gas was measured, and EL was calculated. There was a significant Ve- and time-dependent effect on EL. Initially, percent PFC saturation and loss rate decreased in the VeH > VeM > VeL groups, but by 3 h the lower percent PFC saturation resulted in a loss rate such that VeH < VeM < VeL at 4 h. For the groups at constant Ve, there was a significant time effect on EL but no RR effect. In conclusion, EL profile is dependent on Ve with little effect of the RR-tidal volume combination. Thus measurement of EL and Ve should be considered for the replacement dosing schemes during partial liquid ventilation.