Noninvasive Assessment of the Digital Volume Pulse

Abstract

Abstract-The digital volume pulse can be recorded simply and noninvasively by photoplethysmography. The objective of the present study was to determine whether a generalized transfer function can be used to relate the digital volume pulse to the peripheral pressure pulse and, hence, to determine whether both volume and pressure pulse waveforms are influenced by the same mechanism. The digital volume pulse was recorded by photoplethysmography in 60 subjects (10 women, aged 24 to 80 years), including 20 subjects with previously diagnosed hypertension. Simultaneous recordings of the peripheral radial pulse and digital artery pulse were obtained by applanation tonometry and a servocontrolled pressure cuff (Finapres), respectively. In 20 normotensive subjects, measurements were obtained after the administration of nitroglycerin (NTG, 500 g sublingually). Transfer functions obtained by Fourier analysis of the waveforms were similar in normotensive and hypertensive subjects. In normotensive subjects, transfer functions were similar before and after NTG. By use of a single generalized transfer function for all subjects, the radial and digital artery pressure waveforms could be predicted from the volume pulse with an average root mean square error of 4.4Ϯ2.0 and 4.3Ϯ1.9 mm Hg (meanϮSD) for radial and digital artery waveforms, respectively, similar to the error between the 2 pressure waveforms (4.4Ϯ1.4 mm Hg). The peripheral pressure pulse is related to the digital volume pulse by a transfer function, which is not influenced by effects of hypertension or NTG. Effects of NTG on the volume pulse and pressure pulse are likely to be determined by a similar mechanism. (Hypertension. 2000;36:952-956.)Key Words: plethysmography Ⅲ hypertension, essential Ⅲ pulse Ⅲ nitroglycerin Ⅲ tonometry A digital volume pulse (DVP) can be obtained by measuring infrared light transmission through the finger (photoplethysmography). 1-3 The pioneering work of Takazawa et al 4 has shown that the DVP resembles the carotid pressure wave and varies, as does the carotid pressure wave, with vasodilator and vasoconstrictor drugs. Analysis of this pulse waveform has been used to characterize the effects of aging and of vasodilator drugs on the circulation. 4 However, the physical characteristics that determine the volume pulse waveform are not fully understood. By contrast, the peripheral pressure pulse derived from the radial or digital artery has been subject to much analysis by O'Rourke and colleagues, 5-7 who have established that the peripheral pressure pulse is influenced by pressure wave reflection mainly from the lower body and by pressure wave velocity. Transmission along the upper limb also influences the radial or digital artery pressure pulse (P rad and P dig , respectively), but this influence remains approximately constant across subjects and during the administration of systemically acting vasodilator drugs. 8 Thus, changes in the peripheral pressure pulse are determined mainly by changes in pressure wave reflection within the trunk and lo...

Comparison of photoplethysmographic and arterial tonometry-derived indices of arterial stiffness

“…It has been stated that the DVP obtained by photoplethysmography and pressure pulse waveforms assessed by tonometry have a complex relation that is not fully understood. 24 In this study, active smoking and BMI were factors independently associated with the SI, whereas arterial hypertension and cholesterol level were the independent determinants of the aortic AIx.…”

Assessment of aortic stiffness by local and regional methods

“…26,27 Currently, the most popular method for evaluating arterial stiffness is obtained by estimating the pulse transit time between the carotid and femoral arteries using the tonometric technique. 8,19 This technique gives a reliable index of the regional AoStiff, 28,29 but represents only an estimate of the local AoStiff because it is a summation of the individual biomechanical properties of different arterial walls (that is, carotid, aorta, iliac and femoral arteries) located between the two recording sites.…”

Comparative study of methodologies for pulse wave velocity estimation

“…This device estimates the SI by analyzing the photoplethysmographic waves (digital volume pulse) acquired on the fingertip of the subject. 23 The determining form of SI is shown in Figure 2. All statistical analyses were performed using the NCSS Statistical software.…”

“…[18][19][20][21][22] A surrogate of PWV, the stiffness index (SI), has also been proposed by assessing capillary consequences of arterial stiffness using photoplethysmography, although some studies have showed a feeble correlation between SI and carotid-femoral PWV (PWV cÀf ). [23][24][25] The calculation of propagation time can be measured by various means, including analyzing the foot of the pulse wave, the points of maximum upslope or peak-to-peak time.…”