Utility of electrical impedance tomography to measure neonatal pulmonary circulation changes: a lamb study

Electrical impedance tomography (EIT) has been proposed as a bedside method of measuring pulmonary blood patterns in neonates. However, EIT's use has been limited by technical issues including cardiac-motion artefact and ventilation masking the heartbeat-related signals (HRS). This study aims to determine EIT-derived pulmonary blood volume patterns in two distinct biological models.

The HRS were extracted from EIT recordings during Study A: 10 ml saline administered into the right atrium of apnoeic lambs (n = 6) with cardiac output, and during asystole. Study B: A sustained inflation (aeration without tidal ventilation) during the respiratory transition at birth in preterm lambs (n = 12).

Study A: There was a significant fall in HRS-impedance within lung regions upon administration of saline that was independent of cardiac output (p < 0.0001, Two-way repeated-measure ANOVA), which was not influenced by cardiac motion (p = 0.16), suggesting EIT can detect changes to pulmonary arterial bed blood volume. Study B: The amplitude of the HRS decreased linearly during aeration (R² = 0.062; linear regression) as a net result of decreased diastolic and increased systolic HRS.

EIT demonstrated expected pulmonary blood volume changes in the lung independent of cardiac motion, highlighting EIT's potential to measure ventilation and pulmonary circulation mismatch in neonates.

EIT may represent a future potential solution to the lack of non-invasive and radiation-free measurements of ventilation and pulmonary perfusion in neonates. Our study showed that EIT can detect changes in thoracic impedance that are independent of ventilation and heart motion within the chest and can delineate pulmonary vascular changes that occur at birth. This suggests EIT could be used to detect blood volume changes in the lungs of neonates in the immediate postnatal period.