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; E_L), 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: Ve_L (low-range Ve, 208 ± 2), Ve_M (midrange Ve, 250 ± 9), and Ve_H (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 E_L was calculated. There was a significant Ve- and time-dependent effect on E_L. Initially, percent PFC saturation and loss rate decreased in the Ve_H > Ve_M > Ve_L groups, but by 3 h the lower percent PFC saturation resulted in a loss rate such that Ve_H < Ve_M < Ve_L at 4 h. For the groups at constant Ve, there was a significant time effect on E_L but no RR effect. In conclusion, E_L profile is dependent on Ve with little effect of the RR-tidal volume combination. Thus measurement of E_L and Ve should be considered for the replacement dosing schemes during partial liquid ventilation.