Effectiveness of Ultrasound-guided Lung Ventilation in Determining the Optimum Inspiratory Pressure in Pediatric Patients

Respiratory physiology is different in young children, especially in neonates and infants, from that of older children and adults. Neonates and infants have immature respiratory control, weak respiratory muscles, different airways, lung mechanics and higher basal metabolic oxygen requirements. Appreciating these distinctive respiratory characteristics in young children is necessary to formulate suitable anesthetic plans for the safe conduct of anesthesia as respiratory-related morbidity and mortality occur even in healthy children.

Atelectasis is a side effect of general anesthesia which can be found in all types of interventions and patients of all ages. The reported incidence of anesthesia-induced atelectasis in children varies from 12 to 42% in sedated and non-intubated patients and from 68 to 100% in children with general anesthesia with tracheal intubation or laryngeal mask.

Such lung collapse causes arterial blood oxygenation to decline during and after anesthesia. Although anesthesia-induced atelectasis resolves spontaneously in children with American Society of Anesthesiology's (ASA) physical status classification I to II after minor surgical procedures, this entity may persist in the postoperative period in high-risk children undergoing complex surgeries. In the latter population, atelectasis potentially increases the risk for ventilator-induced lung injury and could be associated with postoperative pulmonary complications.

Atelectasis and poorly ventilated lung areas appear during general anesthesia in adults as well as in children. It is of concern that collapsed lung tissue reduces lung compliance and causes venous admixture and arterial oxygenation impairment. Despite its high prevalence during anesthesia, bedside diagnosis of atelectasis remains challenging. Anesthesia-induced atelectasis is commonly small and thus mostly invisible on standard chest radiographs. In contrast, it can easily be diagnosed by tomographic imaging techniques such as computed tomography or magnetic resonance imaging (MRI). However, these latter are clinically impractical, expensive, time-consuming, and with harmful exposition to x-ray.

Sonography is a simple, non-invasive, and radiation-free methodology that has increased daily practice usage. Lung sonography (LUS) plays an important role in diagnosing pulmonary diseases in children, including obstructive and compressive atelectasis of different origins. Just as in adults, LUS could identify children needing a recruitment maneuver to re-expand their lungs and help optimize ventilator treatment during anesthesia. LUS could also identify critically ill children with a high risk for developing pulmonary complications due to residual atelectasis after surgery.

A prospective, randomized, double-blind study in the Second Affiliated Hospital and Yuying Children Hospital of Wenzhou Medical University showed that an inspiratory pressure of 12 cm H2O was sufficient to provide adequate ventilation with a lower occurrence of gastric insufflation during induction of general anesthesia in paralyzed Chinese children aged from 2 to 4 years old.

Many studies used LUS to determine the optimum positive end-expiratory pressure (PEEP), yet no previous studies used LUS to determine the best inspiratory pressure (IP) for pressure controlled ventilation. So, this study aimed to determine the appropriate level of inspiratory pressure sufficient to provide adequate pulmonary ventilation with the resolution of anesthesia-induced lung atelectasis using real-time ultrasonography in paralyzed children.