Lung Function Monitoring During Hypoxemia Episodes

This is an observational study evaluating changes in lung volume during hypoxemia episodes (HEs or desaturation episodes) in spontaneously breathing very preterm infants. We postulate that HEs can be differentiated into distinct subtypes based on alterations in lung volume. Additionally, the severity and duration of HEs correlates with the degree of changes in lung volumes. Therefore, we are performing an observational study in very preterm infants with spontaneous HEs and classifying these episodes into different subtypes of Apnea, forced exhalation, mixed, and unclassified subtypes according to changes in lung volume. Lung volume will be measured non-invasively using electrical impedance tomography (EIT) device (Sentec Inc, RI, USA). In brief, the device consists of a soft belt with 32 embedded electrodes which is placed around the chest of the infant and applies a weak alternating current and measures returning voltage. The measured returning voltage is dependent on the electrical conductivity of the underlying tissue. The reconstruction algorithm creates an image of regional impedance distribution in real time. These data are then used to compute lung volume parameters at different phases of respiratory cycle providing end expiratory lung impedance reflective of EELV, tidal impedance reflective of tidal volume, and regional distribution of ventilation. The changes in lung volume parameters will be used to differentiate HEs into different subtypes and correlated with degree and severity of HEs. In addition, we will also measure cerebral tissue oxygen saturation (CrSO2) to monitor changes in tissue oxygenation with hypoxemia episodes and changes in lung volume.