Noninvasive measurement of vascular compliance by a photoplesythmographic technique

摘要

Abstract: We describe a simple and robust alternative to ultrasonic methods for the measurement of pulse propagation velocity (PWV) which detects the passage of the diameter wave as it passes two sites a known distance apart. Two probes each containing an infra-red emitting diode and a phototransistor are placed on the skin near to the vessel of interest. The energy returning to each probe depends on the amount of blood the beam has passed through, and this varies as the vessel pulsates. The output from each probe is displayed in real time on a portable PC. PWV is estimated beat-by-beat from the delay between the start of the systolic upswing in the signals from the two sites. In order to verify that our device measures changes in arterial diameter its signals were compared to those obtained simultaneously from an echo tracking pulsed ultrasound system. Transit time measurements from the two devices on the radial and femoral arteries in 6 subjects agreed closely. Additional validation experiments on 21 subjects undergoing cardiac catheterization have shown that transcutaneous measurements of PWV using the infra-red device agree well with intra-arterial measurements obtained with a cannula and pressure transducer. We conclude that the optical technique for measuring PWV is a useful addition to the methods available for determining blood vessel elasticity. Its simplicity and ease of use make it suitable for large scale measurements in the 'field.' Three such studies are currently in progress. !21