Respiration monitoring equipment - uses phase variation of trans-thoracic signal to identify respiratory activity

摘要

The appts. uses two electrodes in the thorax to measure the impedance across the thorax. This is used as an indication of the respiratory action occurring in either a human or animal patient. In order to avoid sensitivity to variations in the mean impedance a high frequency signal is introduced and the modulation of phase, not amplitude of the resultant current is monitored. Each respiration is identified by differentiating the respiratory curve obtained after demodulation of the phase of the signal, and only counting the changes in the curve when the consecutive variations of the signal exceed a threshold value. This process is intended to eliminate counts due to the cardiac activity. The identification of respiration by the patient is followed by an integration process to indicate the patient's mean respiratory frequency.