The effect of induction of anesthesia and intubation on end-expiratory lung level and regional ventilation distribution in cardiac children

Background: During the induction of anesthesia, changes in functional residual capacity and ventilation distribution (VD) occur. Although these physiological changes are well investigated in adults, little data are available in infants and children. Aim: To describe continuous changes in lung physiology during the induction of anesthesia in infants and children using electrical impedance tomography (EIT). Methods: Lung mechanics and volume changes in 38 infants and children undergoing elective cardiac surgery were assessed using EIT before, during, and after the induction of anesthesia. End-expiratory level (EEL as an equivalent to FRC) and VD were measured with EIT and referenced to a period of spontaneous breathing prior to induction. Results: EEL changed significantly during induction with the lowest during the intubation phase and normalized with the application of positive end-expiratory pressures (PEEP) after induction. Ventilation prior to induction was preferentially distributed toward the dependent lung, whereas after induction, the nondependent lung was better ventilated. PEEP during mechanical ventilation did not improve ventilation inhomogeneity. Conclusion: Lung volume and mechanics deteriorate significantly during the induction of anesthesia and remain altered during mechanical ventilation.