Equivalent circuit model for finding the optimum frequency range for the detection of heart failure using microwave systems

A circuit model is used to estimate the useful frequency bands that can be used in a microwave system designed for heart failure detection. That detection is realized by monitoring the accumulation of fluids in lungs (pulmonary edema) that is associated with heart failure. The circuit model is derived from the electrical properties of human tissues in the torso area. To include the effect of the variation in the electrical properties of human lungs due to respiration, the model considers the two normal situations of human lungs (inflated and deflated). It is shown that the attenuation of the signal increases significantly with frequency as expected in any lossy medium. However, using a suitable coupling medium reduces the attenuation and makes it almost constant across the frequency band from 0.5 GHz to around 1 GHz. The attenuation increases rapidly beyond that band. The results presented in this initial work suggest that the band from 0.5 GHz to 1 GHz is suitable for the detection of heart failure, especially when using a proper coupling medium.