A narrative review of electrical impedance tomography in lung diseases with flow limitation and hyperinflation: methodologies and applications

Abstract

Electrical impedance tomography (EIT) is a functional radiation-free imaging technique that measures regional lung ventilation distribution by calculating the impedance changes in the corresponding regions. The aim of the present review was to summarize the current literature concerning the methodologies and applications of EIT in lung diseases with flow limitation and hyperinflation. PubMed was searched up to May 2020 to identify studies investigating the use of EIT in patients with asthma, bronchiectasis, bronchitis, bronchiolitis, chronic obstructive pulmonary disease, and cystic fibrosis. The extracted data included study design, EIT methodologies, interventions, validation and comparators, population characteristics, and key findings. Of the 44 included studies, seven were related to simulation, animal experimentation, or reconstruction algorithm development with evaluation on patients; 27 studies had the primary objective of validating EIT technique and measures including regional ventilation distribution, regional EITspirometry parameters, end-expiratory lung impedance, and regional time constants; and 10 studies had the primary objective of applying EIT to monitor the response to therapeutic interventions, including various ventilation supports, patient repositioning, and airway suctioning. In pediatric and adult patients, EIT has been successfully validated for assessing spatial and temporal ventilation distribution, measuring changes in lung volume and flow, and studying regional respiratory mechanics. EIT has also demonstrated potential as an alternative or supplement to well-established measurement modalities (e.g., conventional pulmonary function testing) to monitor the progression of obstructive lung diseases, although the existing literature lacks prediction values as references and lacks clinical outcome evidence.

Mucosa-interfacing electronics

“…For instance, measuring changes in vaginal mucus impedance and uterine contractile electrical activity in pregnant women can be used to predict delivery time and identify abnormal labour conditions 14 . Similarly, pulmonary mucosal impedance directly reflects pulmonary function and can be used to monitor diseases such as pneumonia and asthma 15 . The slow-wave potential, a rhythmic electrophysiological event in the gastrointestinal (GI) tract, is highly correlated to gastric functions 16 , 17 .…”

Pulmonary rehabilitation ameliorates regional lung function in chronic obstructive pulmonary disease: a prospective single-arm clinical trial

“…The short training period may be the reason why there was no significant difference between FEV 1 /FVC and SVC. (12). The use of EIT is useful for clinicians to observe changes in regional lung function over a period of time to quantify pulmonary disease progression, which may be beneficial to patients with COPD with their heterogeneous pattern of structural and functional lung damage (26).…”

“…Spirometry plays an important role in evaluating the treatment of COPD, but it is derived from the measurement taken at the mouth, so it can only provide the global, average lung function information of patients (11). Since many lung diseases, including COPD, are characterized by regionally dissimilar evolution of the underlying morphological and pathophysiological lung changes, it is essential to assess regional lung function in those patients, which cannot be achieved by conventional detection equipment (12).…”

Unshrinking the baby lung to calm the VILI vortex

“…However, several studies have demonstrated that the injured lung has a far more heterogeneous distribution of parenchymal mechanical properties. Techniques that may be used to further assess such intraparenchymal heterogeneity include electrical impedance tomography [ 39 , 41 ], computed tomographic image registration [ 42 , 43 ] and oscillometric measurements of respiratory impedance [ 44 ]. How any of these approaches may be used to further refine the ventilation modality will of course require further investigation.…”