On modelling respiratory arrhythmia of heart rate

Abstract

Respiratory sinus arrhythmia of heart rate (RSA) is a confounding factor in the measurement of short-term heart rate changes. A cybernetic modelling of the influence of respiration on heart rate was developed and implemented in an analogue-computer simulation of RSA, which is suitable for real-time correction of heart rate measurements in psychophysiological experiments. Since purely linear dynamic models provide a poor match to the physiological heart rate response, its dependence on the direction of breathing ("rein control"), described by Martin Clynes (1961, 1969), was modelled in a non-linear model with a rectifier stage, by superposition of two linear models. This non-linearity made it possible to achieve a particularly accurate simulation, allowing parameter adaptation to the individual subject. Phasic reactions of heart rate, such as its orienting response or other evoked heart rate responses, can thereby be investigated more accurately. The adjusted heart rate signal could further be used as a real-time measure of stress relaxation, e.g. during systematic desensitization. We further developed a non-invasive technique for an exact measurement of breathing volume, by which clients were impeded as little as possible for comfortable use in, e.g., a psychotherapeutic setting. The theoretical principles of RSA extraction and system-theoretical modeling are presented and discussed. — Clynes M (1961). Unidirectional rate sensitivity: A biocybernetic law of reflex and humoral systems as physiologic channels of control and communication. Ann. N. Y. Acad. Sci. 92, 946 - 969. — Clynes M (1969). Cybernetic implications of rein control in perceptual and conceptual organization. Ann. N. Y. Acad. Sci. 156(2), 629 - 670.