Abstract: For detecting tachyarrhythmia of the heart, the partial pressure of gases physically dissolved in the blood is measured, preferably the partial oxygen pressure pO.sub.2, and a fast variation and/or a variation of the measured partial pressure pO.sub.2 that exceeds a prescribed degree is utilized as a criterion for the detection of a tachyarrhythmia. An apparatus for treating tachyarrhythmia of the heart operating according to the above method includes a sensor for identifying the partial pressure of gases dissolved in the blood, an evaluation unit supplied with the sensor output for recognizing rapid changes of the partial pressure or changes of the partial pressure that exceed a prescribed degree, the output of the evaluation unit being connected to circuitry for triggering the tachyarrhythmia treatment.

Abstract: A method and apparatus for calculating a parameter for a physiological function wherein, given a measurement signal influenced by more than one physiological function parameter, signal components of the measurement signal arising from a parameter not of interest are filtered out such that a period duration inversely proportional to the respective current frequency of the parameter not of interest is continuously identified and a mean value of the measurement signal is continuously formed over the identified period duration.