A Multi-Resolution Approach to the Assessment of Pleural Effusion in a Pig Model Using Multi-Frequency Transthoracic Bioimpedance

Pleural effusion (PE) affects millions of people and is caused by a wide variety of underlying diseases. The excess of fluid in the pleural cavity leads to shortness of breath and increased risk for infections that require timely interventions. Yet, existing clinical assessments lack the temporal resolution for continuous monitoring of PE and associated respiratory symptoms. Novel wearable technologies capable of measuring multi-frequency transthoracic bioimpedance (BioZ) continuously hold promise for PE monitoring. In this study, we evaluated the feasibility of monitoring a bilateral PE in a pig model using continuous multi-frequency transthoracic BioZ obtained with a previously-validated wearable device. A novel multi-resolution approach yielded strong and significant correlations to the infused PE at the DClbaseline, respiratory windows, and breath-by-breath resolutions. A total of 1.65 L of saline was infused bilaterally, first left then right, in steps of 275 mL. The low-frequency DC resistance yielded the strongest correlation to the PE size (R<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>=O.99, −14%/L, p<O.OOI), followed by the high-frequency resistance, low-to-high-frequency resistance ratio, and features extracted at the respiratory resolution. This wearable-based approach holds promise for enabling the simultaneous quantification of fluid surrogates and respiratory markers for the continuous and convenient monitoring of PE in clinical settings using transthoracic BioZ.