Electrical impedance tomography identifies a distinct change in regional phase angle delay pattern in ventilation filling immediately prior to a spontaneous pneumothorax

Abstract

Pneumothoraxes are common in preterm infants and are a major cause of morbidity. Early detection and treatment of pneumothoraxes are vital to minimize further respiratory compromise. Electrical impedance tomography (EIT) has been suggested as a method of rapidly detecting pneumothoraxes at the bedside. Our objective was to define the EIT-derived regional phase angle differences in filling characteristics before and during spontaneous pneumothoraxes in preterm lambs. Preterm lambs (124–127-day gestation) were ventilated with high-frequency oscillatory ventilation for 120 min. EIT data and cardiorespiratory parameters were monitored continuously and recorded for 3 min every 15 min. Six animals spontaneously developed a pneumothorax within a gravity-nondependent quadrant of the lung and were included for this analysis. Changes in end-expiratory lung impedance (EELI), ventilation, and phase angle delay were calculated in the four lung quadrants at the onset of the pneumothorax and 15 and 30 min prior. At the onset of the pneumothorax, all animals showed a clear increase in EELI in the affected lung quadrant. Fifteen and thirty minutes before the pneumothorax there was a significant phase angle delay between the nondependent and dependent lung. At 1 min before pneumothorax this phase angle delay was isolated just to the affected quadrant (nondependent). These findings are the first description of the events within the lung at initiation of a pneumothorax, demonstrating distinct predictive changes in air-filling characteristics before the occurrence of pneumothorax. This suggests that EIT may be able to accurately identify the onset of a pneumothorax. NEW & NOTEWORTHY In this article we describe for the first time predictive changes in electrical impedance tomography-based regional filling characteristics of the lung before the onset of a one-sided pneumothorax in six preterm lambs ventilated with high-frequency oscillatory ventilation. This can give clinicians bedside information to change treatment of preterm infants and prevent pneumothorax as life-threatening event from happening.