Identifying Optimal Positive End Expiratory Pressure With Electrical Impedance Tomography Guidance in Severe Bronchopulmonary Dysplasia

Abstract

Background:

Heterogenous lung disease with regional atelectasis and hyperinflation in severe bronchopulmonary dysplasia (BPD) pose challenges in finding optimal PEEP. Current bedside data, including respiratory mechanics, flow volume loop,s and chest radiography, are non-specific to regional inflation. Electrical impedance tomography (EIT) is a noninvasive bedside tool that monitors regional lung ventilation and can augment assessment of lung mechanics. Electrodes are placed on the patient’s chest and impedance is measured when alternating electrical currents transmit across the thorax.

Methods:

This was a single-center, prospective case series. Evaluations were completed as permitted by the institutional review board (protocol 2020P003196). EIT data were collected with an impedance tomograph belt (Timpel, San Diego, CA). The belt was wrapped around subjects’ chest in non-restrictive manner along the T4 nipple line. A flow sensor was placed at the proximal airway in the ventilator circuit. Monitoring parameters included ventilator data, physiologic bedside data, and EIT parameters. Baseline measurements were taken prior to decreasing the PEEP. Alteration of PEEP by 2 cm H₂O occurred after a period of stability of EIT and clinical data. Downward PEEP titration ended when there was evidence of atelectasis or decreased pulse oximetry. When atelectasis, or loss of ventilation, was noted from EIT data, PEEP was increased by 2 cm H₂O.

Results:

Four EIT evaluations were completed for infants hospitalized in the Pediatric and Neonatal Intensive Care Units at Massachusetts General Hospital for Children. In three evaluations, regional lung overdistension was observed on baseline PEEP. Therefore, a cumulative reduction of PEEP by 33% (reduction of 4 cm H₂O per patient). Average supplemental oxygen requirements also decreased (mean 0.77 to 0.28). These changes were maintained for 7 months, 1.5 months, and 3 weeks, respectively. The final patient was experiencing worsening hypoxemic respiratory failure, yet EIT confirmed baseline PEEP was optimal, as overdistension was noted on increased PEEP.

Conclusions:

We have demonstrated the feasibility and safety of EIT-guided PEEP titration in preterm infants less than 6 months old with severe BPD. Data collected through these EIT evaluations triggered changes to clinical care that were not triggered by any other bedside or laboratory data. This study contributes to the growing evidence of validating neonatal applications of EIT.