RESUMO
We aimed to validate a new method for measuring arterial pulsewave transit time and pulsewave velocity (a measure of arterial elasticity), based on the principle of photoplethysmography (PPG), and to compare transcutaneous values with those obtained by intra-arterial measurements. Three validation experiments are described. (a) PPG pulse wave delay times (defined as the time interval between the ECG R wave and the foot of the arterial pulse wave measured at the wrist or ankle) were compared to values obtained simultaneously from an established methodology (Doppler ultrasound). (b) Aortic pulsewave delay times in 17 subjects obtained non-invasively by the PPG method were compared with those obtained from the intra-arterial pressure wave. (c) Repeatability measurements of PWV on the same subjects were carried out over two timescales (minutes and hours) in the arm, the leg and the trunk. The Doppler and PPG delay times correlated well, as did intra-arterial and transcutaneous values. Repeatability at short timescales was good (coefficients of variation (CV) < 6% for all measurement sites) and, at the longer timescale, was satisfactory (CVs in the aorta, the arm and leg were 6.3, 13.1 and 16.0, respectively). The PWV values agreed well with others in the literature. We conclude that the PPG technique provides a complement to existing methods for the non-invasive measurement of arterial compliance. Its simplicity and ease of use make it suitable for large-scale epidemiological studies.
