Electrical impedance tomography assessment of lung homogeneity in infants undergoing inguinal hernia surgery; a prospective cohort study

Mechanical ventilation is often required to support respiratory function but it can cause lung injury. This risk is well understood in the Intensive Care Unit setting where mechanical ventilation is often required for long periods of time but the impact of short exposure to mechanical ventilation during anaesthesia is unknown. Some populations, in particular neonates and small infants, are at greater risk of this potential detrimental effect. One of the principal factors related to ventilator induced lung injury is the inhomogeneity of lung ventilation. To evaluate lung homogeneity, imaging techniques are usually used, although these are often invasive, intermittent and time consuming. Recently a new technology, called Electrical Impedance Tomography (EIT), has been developed. EIT is a non-invasive, radiation-free monitoring tool that allows real-time continuous imaging of ventilation at the bedside, measuring the impedance of the thorax through a belt placed around patient's chest. This study will use EIT to define the patterns of tidal ventilation within the chest in infants undergoing inguinal hernia surgery with three different anaesthetic types, two where they are spontaneously breathing, and one where they are having a general anaesthetic with mechanical ventilation. This study will determine whether mechanical ventilation during general anaesthesia increases the risk of lung inhomogeneity in neonates and small infants. We also hope to determine if there is a correlation between the degree of lung inhomogeneity and the three types of anaesthetic techniques. These results could improve our knowledge about the impact of mechanical ventilation on the neonatal lung and help us to find best management for neonatal ventilation during an anaesthetic, as well as optimal anaesthesia management for infants undergoing surgery.