Monitoring of Lung Ventilation Through Electrical Impedance Tomography During Pediatric Surgery

Anesthesia for surgery is associated with the development of atelectasis and hypoventilation that may persist postoperatively, exposing patients to postoperative pulmonary complications. The main cause is the loss of muscle tone, especially of the diaphragm, which is affected by the pressure exerted by the abdominal viscera, resulting in elevation and compression of alveoli and small airways in the posterior lung regions, leading to collapse and atelectasis, as well as redistribution of ventilation. These variations are even more pronounced in pediatric patients, who have significantly greater chest wall compliance and markedly lower functional residual capacity compared to adults, making them physiologically predisposed to derecruitment during anesthesia. These phenomena are well recognized, but their magnitude and causes are relatively poorly documented due to the scarcity of means capable of precise assessment. EIT is an extremely useful tool as it allows real-time monitoring of changes in the topographic distribution of ventilation in a completely non-invasive manner, highlighting atelectasis and redistribution of aeration. EIT is an imaging technique used in both pediatric and adult patients, analyzing tissue resistivity properties against low-intensity currents applied to the chest via electrodes placed at the IV-VI intercostal spaces. Scans are generated from the collected potential differences and known excitation currents using weighted back-projection into a matrix of pixels. Each pixel represents the instantaneous relative local impedance change compared to a baseline, caused by the presence of a larger or smaller volume of air. This allows for real-time and precise reconstruction of lung air distribution for each breath using dedicated software. In adults, its application in the operating room allows monitoring of lung ventilation distribution during anesthesia, mechanical ventilation, and surgical procedures capable of altering it (such as pneumoperitoneum), optimizing ventilatory settings to avoid atelectasis and derecruitment. Studies in the pediatric field have shown great promise but are significantly limited, mostly conducted in extreme age groups (premature and neonatal) and almost exclusively during spontaneous breathing and without sedation. Pediatric patients undergo a series of respiratory system modifications from birth to adolescence due to lung and alveolar growth, ossification of the rib cage, and muscle tone increase, making the generalization of parameters and findings impossible. Children undergo a series of respiratory system modifications from birth to adolescence due to lung and alveolar growth, ossification of the rib cage, and increased muscle tone, making it impossible to generalize physiological parameters and findings that can vary significantly across different age groups (neonate, infant, preschool-age child, child, adolescent).

Given the scarcity of studies aimed at assessing the effect of anesthesia and surgical technique on the distribution of lung ventilation in pediatric patients undergoing surgery, with the exclusion of thoracic surgery, the present prospective observational study would shed the light on ventilation practice in pediatric anesthesia for surgery. This study wold fill the actual gap allowing the evaluation, through EIT of the distribution of lung ventilation across the different phases of anesthesia for pediatric surgery. These insights could contribute to improve clinical practice and research in the management of ventilation in pediatric patients undergoing anesthesia for surgery.