Linear and non-linear effects in the beat-by-beat variability of sympathetic discharge in decerebrate cats

Heart rate variability and efferent sympathetic discharge are studied in decerebrate and artificially ventilated cats on a beat-by-beat basis. While spectral analysis evidenced the usual low frequency and high frequency rhythms, further analysis at times demonstrated the presence of non-linear effects between the low frequency waves in sympathetic discharge and the high frequency pattern of ventilation. Poincaré´ maps, e.g. of sympathetic discharge vs. ventilation, are proposed for the detection of these phenomena.