Patent ID: 8209011

Claim:
A minute ventilation sensing device, comprising: excitation current electrodes for imposing a current field in the thoracic cavity; an exciter for supplying excitation current as an excitation current waveform at a specified excitation frequency and amplitude between the excitation current electrodes; a plurality of selectable voltage sense electrodes for generating a voltage sense signal corresponding to a potential difference between two points in the thoracic cavity; sampling circuitry for sampling the voltage sense signal during the excitation waveform at a specified sampling rate that corresponds to the excitation frequency; circuitry for demodulating and filtering the voltage sense signal samples into a ventilation band to thereby generate a ventilation signal; circuitry for deriving a signal proportional to minute ventilation from the ventilation signal; circuitry for detecting noise when no excitation current is supplied by filtering the voltage sense signal when no excitation current is supplied into the ventilation band and for computing an average noise level; a switch matrix with the capability of switching between different voltage sense electrode configurations; circuitry for operating the switch matrix to sequentially test the average noise level of a plurality of voltage sense electrode configurations.