Introduction: Chest wall in children is more compliant, slow twitch muscle fibers are less than adults and the alveolus are smaller in size and lesser in number. Airways are more expandable and smaller in diameter. In the other hand the inhalational anesthetics can cause respiratory depression and rapid shallow ventilation. These changes can cause microatelectasia, low respiratory system compliance and increase in work of breathing. Controlled ventilation probably will prevent these events. This study is going to compare behaviors of respiratory system under inhalational anesthesia.Materials and Methods: In a clinical trial, 60 pediatric patients between 6 months to 6 years of age, ASA I & II, who were candidates of elective surgery on extremities and lower abdomen, entered to study. Patients were randomly allocated in two groups of spontaneous and controlled ventilation. In the first group inhalational and in the second group intravenous inductions were performed. Both groups were given halothane (0.8-1 %) in a 50% mixture of N2O and O2 for maintenance of anesthesia. HR, RR, BP, SPO2 and T before induction and all of these plus EVT and peak and plateau APs, 5 minutes after induction and every 15 minutes thereafter were measured and dynamic and static compliance were calculated by using measured data. Data was analyzed by ANOVA, T student and Chi square tests.Results: Patients in spontaneous ventilation group had significantly more RR and EtCO2 and less awakening time (p<0.05).Total mean of HR, SBP, DBP, SPO2, T, PIP, PltIP, dynamic and static compliance after induction of anesthesia had no statistical differences between the two groups.
Conclusion: There are no constant significant differences between the two groups in respiratory system compliance, airway pressures and T and this study can not prove the development of significant changes in respiratory system indices between the two groups. Thus micro atelectasis (if developed) is not clinically important during less than one hour surgeries.