Effects of PEEP on the relationship between tidal volume and total impedance change measured via electrical impedance tomography (EIT)

Abstract

Electrical impedance tomography (EIT) is used in lung physiology monitoring. There is evidence that EIT is linearly associated with global tidal volume (VT) in clinically healthy patients where no positive end-expiratory pressure (PEEP) is applied. This linearity has not been challenged by altering lung conditions. The aim of this study was to determine the effect of PEEP on VT estimation, using EIT technology and spirometry, and observe the stability of the relationship under changing lung conditions. Twelve male castrated cattle (Steer), mean age 7.8 months (SD ± 1.7) were premedicated with xylazine followed by anaesthesia induction with ketamine and maintenance with halothane in oxygen via an endotracheal tube. An EIT belt was applied around the thorax at the level of the fifth intercostal space. Volume controlled ventilation was used. PEEP was increased in a stepwise manner from 0 to 5, 10 and 15 cmH 2 O. At each PEEP, the VT was increased stepwise from 5 to 10 and 15 mL kg −1. After a minute of stabilisation, total impedance change (VT EIT), using EIT and VT measured by a spirometer connected to a flow-partitioning device (VT Spiro) was recorded for the following minute before changing ventilator settings. Data was analysed using linear regression and multi variable analysis. There was a linear relationship between VT EIT and VT Spiro at all levels of PEEP with an R 2 of 0.71, 0.68, 0.63 and 0.63 at 0, 5, 10 and 15 cmH 2 O, respectively. The variance in VT EIT was best described by peak inspiratory pressure (PIP) and PEEP (adjusted R 2 0.82) while variance in VT Spiro was best described by PIP and airway deadspace (adjusted R 2 0.76). The relationship between VT EIT and VT Spiro remains linear with changes in tidal volume, and stable across altered lung conditions. This may have application for monitoring and assessment in vivo.

Assessment of Postnatal Pulmonary Adaption in Bovine Neonates Using Electric Impedance Tomography (EIT)

“…Ventilation was considerably greater in the central regions compared with the peripheral regions, and, in the right lung, the centrodorsal part always had the greatest ventilation. This finding was in agreement with EIT studies in other mammals [ 16 , 56 , 57 ].…”

“…Measurements using EIT in new-born human babies also determined greater ventilation in the right lung [ 54 , 55 ]. The phenomenon that the right lung is preferentially ventilated also in adult mammals has been observed in humans, horses, and steers [ 16 , 56 , 57 ].…”

“…Therefore, compared with the first measurement, the significant differences in ΔZVT from day 6 onward were most likely attributable to an increase in lung volume reflected also by the decrease in NSS and DSS. In young bulls, horses, and people, EIT and spirometry were used in combination, which allowed the calculation of the ventilation volumes with a high degree of accuracy [ 56 , 66 , 67 ]. We did not use spirometry and, therefore, could not determine absolute tidal volumes.…”

The Research Progress of Electrical Impedance Tomography for Lung Monitoring

“…For most people with ARDS, mechanical ventilation is a mature method to maintain normal breathing of patients, but unreasonable ventilator parameters may aggravate the lung condition and even cause serious lung injury (Prost et al, 2011). Therefore, the most common protective ventilation strategy is to reduce lung injury by setting a reasonable PEEP (positive end-expiratory pressure) value (Guerin, 2011;Brabant et al, 2019). As a noninvasive medical imaging technology, EIT can monitor the air distribution of mechanical ventilation in real time by imaging the cross section of thoracic cavity (Blankman and Gommers, 2012;Andiani et al, 2019).…”

A Point-Matching Method of Moment with Sparse Bayesian Learning Applied and Evaluated in Dynamic Lung Electrical Impedance Tomography

“…This makes EIT a useful tool for real-time lung function monitoring. Many studies have shown the importance of EIT for revealing vital signs related to ventilation properties, such as tidal volume (TV) [ 2 ], or pathological situations, such as acute respiratory distress syndrome (ARDS) [ 3 ].…”