Perfluorochemical (PFC) Evaporation from the Lungs: Effect of Body Temperature

Abstract 1835 Poster Session I, Saturday, 5/1 (poster 45)

The benefit of partial liquid ventilation PLV^SM has been shown in a variety of respiratory diseases in animal and human studies. Although the amount of PFC in the lungs should be kept stable during PLV, PFC is lost due to evaporative loss (E_L) which depends on ventilation strategy, positioning, and PFC vapor pressure (P_V). Since P_V rises exponentially with temperature, we hypothesized that PFC E_L profile over time is dependent upon temperature. To quantify the effect of temperature on E_L, 17 ml/kg of perflubron (LiquiVent®) was instilled endotracheally into anesthetized, juvenile rabbits (N = 8; wt= 1.76 ± 0.18 SE kg) over 5-10 minutes after the animals were stabilized at 27°C (core temperature, T_C) for the hypothermic group and 37°CT_C for the normothermic group. The ventilation strategy was to keep the minute ventilation at 300 ml/kg/min and position (supine) constant. Gas exchange and acid base balance were maintained in a physiologic range. T_C was measured with a thermodilution catheter placed I.V. The content of PFC in the expired gas was measured with a previously described thermal detector device and the E_L was calculated. Radiographic images were taken at 4 hrs of PLV. E_L (ml/kg/hr) of PFC (mean ± SE): (Table)

Table 1 No caption available

As shown, there was a significant (p<0.01) interaction between loss rate and T_C, with lower loss of PFC in the hypothermic group. There was approximately a 2 fold decrease in E_L between groups, residual lung PFC was 11.4 ml. (normothermia) and 14.5 ml (hypothermia), and E_L of PFC decreased an average of 0.1 ml/kg/hr per 1°C of T_C. There were distinct differences in radiographic images at 4 hrs showing significantly more PFC in the low T_C group. We conclude that E_L is dependent on body temperature and, in addition to ventilation strategy and positioning, this factor should be considered in supplemental dosing schemes, particularly, for hypothermic or hyperthermic applications of PLV.

[Funded in part by Alliance Pharmaceutical Corporation]