Effects of Halothane, Enflurane and Isoflurane on Compliance and Resistance of the Total Respiratory System in Anesthetized Man / 대한마취과학회지

ABSTRACT

Bronchoconstrictions can occur by stimuli to the airway during anesthesia. Inhalational agents prevent or attenuate brochoconstriction and successfully inhibit reflexes of airway in asthmatic patients, and their mechanisms are well established. However, the effects of inhalational agents on the normal respiratory system is controversial. Therefore we studied the changes of compliance and resistance of the total respiratory system before and after administration of one of halothane, enflurane and isoflurane to unstimulated patients. We selected thirty adult patients without respiratory problems and excluded patients of receiving thoracic and abdomenal surgery because airway pressure might be changed by surgical manipulation. The patients without any premedication were ventilated with 50% oxygen by closed circuit ventilator(Physio-Flex(R)) after slow intravenous injection of thiopental sodium, fentanyl and vecuronium. We randomly allocated patients to one of three inhalational anesthetics( halothane, enflurane, isoflurane group). Then we intubated with I.D. 8 mm sized endotracheal tube for men and with I.D. 7 mm for women. Tidal volume and respiratory rates were maintained constantly during controlled ventilation and we increased concentration of inhalational agent by 0.5 MAC from zero to 1.5 MAC stepwise. At 10 minutes aft/er change of concentration of agent, we checked peak airway pressure, plateau airway pressure, mean airway pressure and end-tidal CO2 and then calculated compliance and resistance of the total respiratory system. We found that neither compliance nor resistance was changed by administration of or increasing concentration of halpthane, enflurane or isoflurane. The unstimulated normal airway in anesthetized patients was may be fully dilated, so that there was no more bronchodilatation after administration of inhalational agents.