Influence of different types of stressors on the waveform of the peripheral arterial pulse in humans

Changes of elastic properties of central arteries during acute static exercise and lower body negative pressure

The aim of this investigation was to determine the acute effects of isometric fatiguing handgrip (IFHG) and lower body negative pressure (LBNP) on indices of central arterial stiffness. Thirteen subjects were studied. Renal blood velocity (Duplex Ultrasound) and blood pressure (Finapres) were monitored during IFHG and LBNP at -30 and -50 mmHg. Radial pulse-wave forms were recorded by applanation tonometry. Central aortic waveforms and other hemodynamic parameters were assessed using the Sphygmocor software. Renal vascular resistance index (RVRI; mean BP/renal blood velocity) was used as index of sympathetic nervous system (SNS) engagement. RVRI increased during both IFHG and LBNP indicating that SNS was engaged; however, BP increased only during the IFHG. Pulse-wave analysis showed that during the IFHG protocol the transit time of the pulse wave decreased and the peripheral pulse pressure/nonaugmented central pulse pressure ratio increased from baseline. Both of these measurements suggest an increase in central large artery stiffness. During LBNP no changes in the indices of central stiffness were noted, in spite of a similar level of sympathetic system engagement. Heart rate increased during both protocols, whereas augmentation index increased during the IFHG protocol and decreased during the LBNP. Our major conclusion was that blood pressure rather than sympathetic activity seems to play the major role in modulating the elastic properties of the central arteries. The decrease in augmentation index during the LBNP protocol can be attributed to the increased heart rate, given that there is a negative correlation between these two parameters.

Pulse wave analysis on fingertip arterial pressure: effects of age, gender and stressors on reflected waves and their relation to brachial and femoral artery blood flow

OBJECTIVES

Analysis of the contour of the arterial pressure pulse (pulse wave analysis; PWA) adds information about arterial stiffness etc., beyond that obtained from absolute pressures. Peripheral pulses normally show an anterograde systolic peak and two reflected peaks: one in systole and one in diastole. The amplitudes and timings of these were estimated from finger pressure recordings in three study groups. We studied the usefulness of continuous digital pressures for PWA.

METHODS

First, PWA from intra-arterial (brachial) and non-invasive finger pressure recordings was compared. Secondly, stress-induced (mental arithmetics and cold pressor test) changes in pressure pulse reflection were compared with blood flow changes in brachial and femoral arteries (ultrasound). Thirdly, the influence of age and gender on digital pulse pressures was investigated at rest and during exercise.

RESULTS AND CONCLUSION

Pulse wave analysis results from brachial and digital pressures correlated strongly. Stress induced changes in systolic reflection were associated with changes in brachial artery flow patterns, whereas diastolic reflection was associated with femoral artery flow changes. At rest, age increased systolic reflection without affecting diastolic reflection. Exercise increased systolic reflection and reduced diastolic reflection more in older subjects (>40 years) than in younger (<40 years). In conclusion, PWA from continuous, digital pressure recordings is a convenient technique to study the arterial function at rest and during exposure to stressors in broad populations. The two reflected waves are differently regulated, which may indicate different anatomical origin.