In this patent of invention there are described a method and an apparatus for obtaining information on the cardiovascular system beat by beat and continuously which are based exclusively on measurements between two limbs and effected with a pair of distal electrodes on each limb. The measurement is made by causing an alternating current to flow between one electrode of each limb and measuring the potential difference between the other two electrodes, one also on each limb. This potential difference has a low frequency component which is the electrocardiogram (or ECG) and another component having the frequency of the injected alternating current and from which the so-called impedance plethysmogram (IPG) is extracted. The cardiovascular information will be determined by measuring the time interval between any predefined characteristic element of the ECG and one of the IPG.
