Thoracic Bioimpedance as a Basis for Pacing Controla

Periodic variations of the thoracic bioimpedance due to breathing and heartbeating carry confidential information that is used for pacing rate control in rate-adaptive pacemakers. The respiratory parameters--the respiration rate and tidal volume--are detected from the filtered breathing signal component (0.1 to 1.0 Hz), and are used for fuzzy feed-forward adaptive control of the pacing rate to meet the needs of the organism. The cardiac parameters--the actual heart rate and stroke volume--are measured from the heartbeating signal component (1.0 to 3.0 Hz) and are proposed for feedback correction of the feed-forward control to meet the heart's ability. The problems of electrical bioimpedance measurement and design of the rate-adaptive pacemaker, wherein the intracardiac impedance is used as the main information source for pacing control, are discussed in this paper.