Fecha de publicación: 28/05/1998 Fuente: WIPO "beekeeper" Apparatus for measuring vagal tone is described which has a detector (10) which detects the QRS waveform of an ECG signal and which generates a pulse signal which is integrated by an integrator (11). The integrator output (11a) is passed, in parallel, to a high pass filter (12) and a low pass filter (13). The filter outputs are passed to respective Voltage Controlled Oscillators (VCO) (15, 16). The outputs of VCOs (15, 16) are combined in a phase comparator (17) which generates an output pulse train with the pulse period being proportional to the phase differences of the input signals. The phase comparator output signal is integrated and combined with a DC signal to remove any offset for constant heart rate. The combined signal is applied to a vagal tone gauge (20) which connects the output into a standard linear vagal tone scale. The apparatus has use in a variety of clinical applications particularly in diagnosing both human and animal autonomic dysfunction conditions.