Patent ID: 6868346
Filing Date: 2005-03-15
Classification: A61N

Abstract:
1. A minute ventilation sensing device, comprising: excitation current electrodes for imposing a current field in the thoracic cavity; an exciter for supplying excitation current between the excitation current electrodes; voltage sense electrodes for generating an impedance signal corresponding to a potential difference between two points in the thoracic cavity when the excitation current is applied; sampling circuitry for sampling the impedance signal; circuitry for filtering the impedance signal samples into a ventilation band to thereby generate a ventilation signal, wherein the filtering circuitry includes a high pass filter with a variable pole frequency for removing a DC component from the impedance signal samples; circuitry for calculating a signal variation parameter from a set of impedance signal samples; circuitry for adjusting a frequency response of the high pass filter to compensate for changes in the calculated signal variation parameter; and, circuitry for deriving a signal proportional to minute ventilation from the ventilation signal.