Mouse model for sensitivity of fluid measurement with textile electrodes

Heart failure is a leading cause of morbidity and mortality, and fluid congestion complicates its management. Conventional home-monitoring methods, such as daily weight measurements, are insufficiently sensitive, while invasive techniques are impractical for routine use. This paper introduces a novel, non-invasive approach using textile-based dry electrodes for bio-impedance spectroscopy to detect subtle changes in thoracic fluid volume in a mouse model. Twenty-three mice underwent controlled fluid infusion into the thoracic cavity following a six-stage protocol. Bio-impedance data were collected over 256 frequencies ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>3</mml:mn> <mml:mo>-</mml:mo> <mml:mn>1000</mml:mn></mml:mrow> </mml:math> kHz) and analyzed to extract <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>R</mml:mi> <mml:mn>0</mml:mn></mml:msub> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>R</mml:mi> <mml:mi>∞</mml:mi></mml:msub> </mml:math> , from which total ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>V</mml:mi> <mml:mi>T</mml:mi></mml:msub> </mml:math> ), extra-cellular ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>V</mml:mi> <mml:mi>E</mml:mi></mml:msub> </mml:math> ), and intra-cellular ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>V</mml:mi> <mml:mi>I</mml:mi></mml:msub> </mml:math> ) fluid volumes were calculated and normalized to baseline. Statistical analyses included two-way ANOVA and multiple linear regression to correlate impedance measurements with animal length and weight. No statistically significant differences in normalized fluid volumes ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>V</mml:mi> <mml:mi>T</mml:mi></mml:msub> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>V</mml:mi> <mml:mi>E</mml:mi></mml:msub> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>V</mml:mi> <mml:mi>I</mml:mi></mml:msub> </mml:math> ) were observed across infusion stages ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>p</mml:mi> <mml:mo>></mml:mo> <mml:mn>0.05</mml:mn></mml:mrow> </mml:math> ), though there was an anecdotal increase in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>V</mml:mi> <mml:mi>T</mml:mi></mml:msub> </mml:math> ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Δ</mml:mi> <mml:msub><mml:mi>V</mml:mi> <mml:mi>T</mml:mi></mml:msub> <mml:mo>=</mml:mo> <mml:mn>1.16</mml:mn> <mml:mo>±</mml:mo> <mml:mn>1.79</mml:mn></mml:mrow> </mml:math> mL) and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>V</mml:mi> <mml:mi>I</mml:mi></mml:msub> </mml:math> ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Δ</mml:mi> <mml:msub><mml:mi>V</mml:mi> <mml:mi>I</mml:mi></mml:msub> <mml:mo>=</mml:mo> <mml:mn>1.80</mml:mn> <mml:mo>±</mml:mo> <mml:mn>2.91</mml:mn></mml:mrow> </mml:math> mL) after fluid infusion. Multiple linear regression revealed moderate correlations between impedance measurements and weight ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msup><mml:mi>r</mml:mi> <mml:mn>2</mml:mn></mml:msup> <mml:mo>=</mml:mo> <mml:mn>0.33</mml:mn></mml:mrow> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>p</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.035</mml:mn></mml:mrow> </mml:math> , RMSE <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>=</mml:mo> <mml:mn>19.34</mml:mn></mml:mrow> </mml:math> g) as well as length ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msup><mml:mi>r</mml:mi> <mml:mn>2</mml:mn></mml:msup> <mml:mo>=</mml:mo> <mml:mn>0.34</mml:mn></mml:mrow> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>p</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.0066</mml:mn></mml:mrow> </mml:math> , RMSE <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>=</mml:mo> <mml:mn>1.00</mml:mn></mml:mrow> </mml:math> cm). Additionally, a strong correlation was found between length and weight ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msup><mml:mi>r</mml:mi> <mml:mn>2</mml:mn></mml:msup> <mml:mo>=</mml:mo> <mml:mn>0.81</mml:mn></mml:mrow> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>p</mml:mi> <mml:mo>=</mml:mo> <mml:mn>5.65</mml:mn> <mml:mo>×</mml:mo> <mml:msup><mml:mn>10</mml:mn> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>8</mml:mn></mml:mrow> </mml:msup> </mml:mrow> </mml:math> ). The results indicate that textile-based dry electrodes can non-invasively measure thoracic fluid volume in mice, although the sensor's sensitivity to small changes is limited. Further refinement is needed to enhance sensitivity and determine sensitivity threshold. These findings support the continued development of textile-based bio-impedance sensors as a practical tool for non-invasive heart failure monitoring.