32 then performs additional computation on the digitized pulse waveform u03b4p o to calculate an estimated intra arterial blood pressure waveform p i using a relationship such as the one shown in fig5 in the preferred embodiment measured brachial intra arterial blood pressure waveforms are used to estimate the pressure waveform at the subclavian root in the aorta p t0 t in this model p t0 t is related to a proximal and distal brachial pressure as shown in fig1 by the formulae p t0 t b b 1 p t3 t u2212 dt 1 b 1 p t3 t dt p t0 t b b 1 p t4 t u2212 dt u2212 u03b4t 1 b 1 p t4 t dt u03b4t the parameters to these formulae are determined using the apparatus described by the block diagram of fig2 in the preferred embodiment the measurement of signals from the proximal and distal suprasystolic cuffs is carried out according to the steps shown in fig2 first both cuffs are inflated to a suprasystolic pressure the intra arterial pressure waves within the brachial artery thus first impinge on the proximal cuff recordings of proximal cuff pressure oscillations and heart activity is made the proximal cuff is then deflated to a subdiastolic pressure allowing the intra arterial pressure waves to impinge on the distal cuff measurements of the distal cuff pressure oscillations and heart activity are made both cuffs are then fully deflated to prevent ischaemia the apparatus described is thus used to provide the following signals the proximal suprasystolic cuff provides a signal that is used to estimate the intra arterial pressure p t3 and the distal suprasystolic cuff provides a signal that is used to estimate the intra arterial pressure p t4 the heart activity sensor which is preferably a.