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Abstract

An implantable medical apparatus for stimulating a heart at a variable stimulation rate dependent on the respiratory rate, tidal volume, heart rate and stroke volume includes a measurement apparatus which measures impedance around the heart, a filter unit which splits the impedance signal into high-frequency and a low-frequency signal portions and two analyzers which respectively evaluate the signal portions and which emit the four parameter values as output signals. The product of respiratory rate times tidal volume is formed in a control apparatus. This product corresponds to respiratory minute volume, and the product of heart rate times stroke volume corresponds to cardiac output. Cardiac output is multiplied by a constant, and respiratory minute volume is subtracted from the product thus formed. The resulting different is equal to zero when blood oxygenation is optimum. The control apparatus controls the stimulation rate on the basis of the magnitude and sign of the difference.

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First Claim