Computer analysis of reflex control and organization: respiratory sinus arrhythmia.

Respiratory sinus arrhythmia in waking man is described by differential equations which relate thorax circumference acceleration to instantaneous heart rate. Consequent experiments show that the arrhythmia is initiated by stretch receptors within the thorax rather than by hemodynamic or central factors, and that it is due mainly to superimposed biphasic inspiratory heart rate transients of about 15 seconds' duration. Analysis of respiration heart rate reflex provides a new quantitative physiological tool.