| abstract |
A metabolic-demand pacemaker in which the standby rate is a function of minute volume. Electrodes are placed in a blood vessel in the vicinity of the patient's pleural cavity, a known current field is established in the blood, and the impedance in the field is measured. The impedance is a function of the pleural pressure which, in turn, is a function of the patient's minute volume. The system also includes a mechanism for calibrating the standby rate to equal the nominal standby rate for a minute volume which equals a long-term average value, with the standby rate being changed in accordance with the deviation of the minute volume from the long-term average value. |