Removing Clinical Motion Artifacts During Ventilation Monitoring With Electrical Impedance Tomography: Introduction of Methodology and Validation With Simulation and Patient Data

Abstract

ObjectiveElectrical impedance tomography (EIT) is a bedside tool for lung ventilation and perfusion assessment. However, the ability for long-term monitoring diminished due to interferences from clinical interventions and motion artifacts. The purpose of this study is to investigate the feasibility of the discrete wavelet transform (DWT) to detect and remove the common types of motion artifacts in thoracic EIT.MethodsBaseline drifting, step-like and spike-like interferences were simulated to mimic three common types of motion artifacts. The discrete wavelet decomposition was employed to characterize those motion artifacts in different frequency levels with different wavelet coefficients, and those motion artifacts were then attenuated by suppressing the relevant wavelet coefficients. Further validation was conducted in two patients when motion artifacts were introduced through pulsating mattress and deliberate body movements. The db8 wavelet was used to decompose the contaminated signals into several sublevels.ResultsIn the simulation study, it was shown that, after being processed by DWT, the signal consistency improved by 92.98% for baseline drifting, 97.83% for the step-like artifact, and 62.83% for the spike-like artifact; the signal similarity improved by 77.49% for baseline drifting, 73.47% for the step-like artifact, and 2.35% for the spike-like artifact. Results from patient data demonstrated the EIT image errors decreased by 89.24% (baseline drifting), 88.45% (step-like artifact), and 97.80% (spike-like artifact), respectively; the data correlations between EIT images without artifacts and the processed were all > 0.95.ConclusionThis study found that DWT is a universal and effective tool to detect and remove these motion artifacts.

The influence of reference electrode in electrical impedance tomography

“…Previous studies attempted to remove the motion artifacts using advance data processing algorithms (e.g. [10]). Time-difference image reconstruction may reduce the requirement of knowing the exact contact impedance of each electrode.…”

Benefits of secretion clearance with high frequency percussive ventilation in tracheostomized critically ill patients: a pilot study

“…Noteworthy, the EIT belt was never moved or removed from the patient and its position checked before every single recording, to assure the recording quality [7,16,17]. In addition, pulsating air suspension mattress was switched off during the study protocol to minimize possible electrical interferences, baseline drifting, step-like and/or spike-like signal [18,19].…”

A quick survey of EEG signal noise removal methods

“…This causes the change in impedance of the electrodes which causes disturbance. This also happens when the patient is lying on electrode and continuously inhaling and exhaling [13].…”

“…These artifacts occur when the impedance between the skin and the electrode change due to natural phenomena of the body [13].…”