A robust and novel electrical impedance metric of pulmonary function in ALS patients

Abstract

Objective: Pulmonary function tests (PFTs) are important for assessing respiratory function in amyotrophic lateral sclerosis (ALS) patients. However, weakness of oral and glottal closure, due to concomitant bulbar dysfunction, may result in unreliable PFT values stemming from leakage of air around the breathing tube and through the glottis. In this study, we assessed whether standard thoracic electrical impedance tomography (EIT) could serve as a surrogate measure for PFTs. Approach: Thoracic EIT was performed simultaneously with standard PFTs on seven ALS patients without clinical bulbar weakness (six men and one woman, mean age of 63 years) and ten healthy volunteers (seven men and three women, mean age of 57 years). A raw impedance metric along with more standard EIT measures were computed and correlated with the normalized forced vital capacity (FVC). Additionally, test/re-test metrics and EIT images were analyzed. Main results: The impedance metric was found to be robust and sensitive to lung activity. We also identified qualitative EIT differences between healthy volunteers and ALS patients, with the ALS images showing greater heterogeneity. Significant correlations with FVC were found for both impedance and EIT metrics in ALS patients (r2 = 0.89) and for the impedance metric only in healthy volunteers (r2 = 0.49). Significance: This suggests that EIT, using our novel impedance metric, has the potential to serve as an alternative technology to standard PFTs for assessing pulmonary function in patients with ALS, offering new metrics of disease status for those with bulbar weakness.

Regional ventilation distribution in healthy lungs: can reference values be established for electrical impedance tomography parameters?

“…The resulting voltages and reconstructed regional impedance values reflect the volume changes of air and blood in the lung tissue (2). Chest EIT applications cover a broad field of clinical practice (3), including the treatment of acute respiratory distress syndrome (ARDS) (4), coronavirus disease 2019 (5)(6)(7), and acute exacerbation of chronic obstructive pulmonary disease under mechanical ventilation (8,9), as well as pulmonary function testing for patients with asthma, cystic fibrosis, and chronic obstructive pulmonary disease (10)(11)(12)(13).…”

Rapid patient-specific FEM meshes from 3D smart-phone based scans

“…EIT images were produced of tidal breathing (differencing the average maximum inhale minus the maximum exhale) from recordings of 30 s of tidal breathing from each subject. The same impedance noise filtering described in Munir et al ( 2020 ) was used here. EIT images were produced by a one-step Gauss–Newton approach with standard Tikhonov regularization and normalized voltage data.…”