Evaluation of Parameters of Gas Exchange During Partial Liquid Ventilation in Normal Rabbit Lung

An, Chang Hyeok; Koh, Young Min; Park, Chong Wung; Suh, Gee Young; Koh, Won Jung; Lim, Sung Yong; Kim, Cheol Hong; Ahn, Young Mee; Chung, Man Pyo; Kim, Ho Joong; Kwon, Jung O

Abstract

BACKGROUND: The opitmal ventilator setting during partial liquid ventilation(PLV) is controversial. This study investigated the effects of various gas exchange parameters during PLV in normal rabbit lungs in order to aid in the development of an optimal ventilator setting during PLV.
METHODS
Seven New-Zealand white rabbits were ventilated in pressure-controlled mode with the following settings; tidal volume(VT) 8ml/kg, positive end-expiratory pressure(PEEP) 4cmH2O, inspiratory-to-expiratory ratio(I:E ratio) 1:2, fraction of inspired oxygen(F1O2) 1.0. The respiration rate(RR) was adjusted to keep PaCO2 between 35~45mmHg. The ventilator settings were changed every 30 min in the following sequence : (1) Baseline, as the basal ventilator setting, (2) Inverse ratio, I:E ratio 2:1, (3) high PEEP, adjust PEEP to achieve the same mean inspiratory pressure (MIP) as in the inverse ratio, (4) High VT, VT 15ml/kg, (5) high RR, the same minute ventilation(MV) as in the High VT. Subsequently, the same protocol was repeated after instilling 18ml/kg of perfluorodecalin for PLV. The parameters of gas exchange, lung mechanics, and hemodynamics were examined.
RESULTS
(1) The gas ventilation(GV) group showed no significant changes in the PaO2 at all phases. The PaCO2 was lower and the pH was higher at the high VT and high RR phases(p<0.05). No significant changes in the lung mechnics and hemodynamics parameters were observed. (2) The baseline PaO2 for the PLV was 312+/-113mmHg. This was significantly lower when decreased compared to the baseline PaO2 for GV which was 504+/-81mmHg(p=0.001). During PLV, the PaO2 was significantly higher at the high PEEP(452+/-38mmHg) and high VT(461+/-53mmHg) phases compared with the baseline phase. However, it did not change significantly during the inverse I:E ratio or the high RR phases. (3) The PaCO2 was significantly lower at high VT and RR phases for both the GV and PLV. During the PLV, PaCO2 were significantly higher compared to the GV (p<0.05). (4) There were no important or significant changes in of baseline and high RR phases lung mechanics and hemodynamics parameters during the PLV.
CONCLUSION
During PLV in the normal lung, adequate VT and PEEP are important for optimal oxygenation.