REAL-TIME MEASUREMENT OF PULSE-WAVE VELOCITY FROM ARTERIAL-PRESSURE WAVE-FORMS

Instrumentation for the real-time clinical measurement of pulse wave v elocity (PWV) from intra-arterial pressure waveforms is presented. The time delay between pressure waveforms (obtained from two intra- arter ial catheter-mounted transducers 5 cm apart) is calculated by a transp uter using multiple comparisons between discrete sections of the wavef orms. The method is validated by analysis of digital and analogue sign als with known time delays and is used to measure changes in PWV in th e right common iliac artery (RCIA) during infusions of acetylcholine ( 2.4, 24 and 240 mu g ml(-1)) in six healthy subjects. The system measu res the delay between digitally shifted triangular waveforms and press ure waveforms to a precision of about 50 mu s, and it is superior to m easurements performed by hand using a high-performance digital storage oscilloscope. When used to measure the effects of acetylcholine on th e RCIA, dose-dependent reductions in PWV are recorded (-8.5%, -11.6%, -14.5%). It is concluded that the instrumentation enables PWV to be me asured with high accuracy and precision in real time, if the pressure signals are of high fidelity and the relative amplification of the sig nals is carefully balanced.