A novel non-invasive, non-conductive method for measuring respiration

We present a novel method for measuring dynamic changes in thoracic parameters due to breathing based on the coupling of two UHF antennas. The phase shift between the antennas as well as the resonance frequency of the coupled antenna pair change with the air volume in a lung phantom. For evaluation, we built a dynamic 3D printed phantom encasing two compartments separated by an elastic diaphragm. By filling this artificial lung with air the effective permittivity in the compartment changes resulting in a detectable phase and frequency shift. We use a vector network analyzer to show that there is a strong linear dependency between the volume of air in the artificial lung and the frequency at which the S21 parameter peaks (R2=0.98). Related to this, we observe a phase shift when looking at a single frequency close to the resonance frequency of the system. This shift is also linearly dependent on the volume of air in the lung (R2=0.998). The presented method is a promising candidate to overcome some of the most important technical burdens of measuring respiratory parameters and might be used as trigger for patient ventilator synchronization in infants and neonates.