Effects of Varying Concentrations of Enflurane on Respiratory System Mechanics in Cats

Shin, Ji Yeon; Lee, Byung Wook; Jung, Wol Sun; Kim, Jong Uk; Park, Pyung Hwan; Lee, Dong Myung

Abstract

BACKGROUND: Flow interruption technique has been used to measure respiratory system mechanics, and its prominent advantage is to partitionate the respiratory system resistance into airway and tissue component. In this study, we investigated the effects of varing concentrations of enflurane on respiratory system mechanics using flow interruption technique.
METHODS
Six cats, weighing 3.0~3.6 kg were used. Pentobarbital sodium was injected intraperitonially and endotracheal intubation was followed. Intermittent mandatory ventilation was applied with Siemens Servo 900C ventilator. The inspiratory flow rate, tidal volume, and respiratory rate were fixed, and normocarbia (PaCO2; 30~35 mmHg) was maintained throughout the experiment. The changes in the pressure and volume were recorded with Bicore CP100 pulmonary monitor at control, 0.5, 1, 1.5, and 2 MAC of enflurane. The data were transfered to a PC and analyzed by Anadat processing software. Respiratory system, airway and tissue viscoelastic resistances, and dynamic and static compliances were calculated.
RESULTS
Respiratory system resistances decreased up to 1 MAC of enflurane compared to the control value (p<0.05), but there were no significant differences in the values of resistance among 1, 1.5, 2 MAC of enflurane. There were no significant differences in tissue viscoelastic resistances, and dynamic and static compliances with varying concentrations of enflurane.
CONCLUSIONS
Enflurane significantly reduces the respiratory system resistance mainly by decreasing airway resistance. Tissue viscoelastic resistance and respiratory system compliances are not influenced by changes in concentration of enflurane.