Microcirculatory Pulse Wave Velocity: A Novel Method Utilizing Near-Infrared Spectroscopy

Abstract

Pulse wave velocity (PWV) is a gold standard assessment for arterial stiffness, which is a well-known marker for cardiovascular diseases. Specifically, PWV is the measurement of the velocity of blood pulse waves traveling across a segment of the arterial network. Although PWV assessment is well-characterized in the conduit arteries with tonometry techniques (TT), PWV to the microcirculation has not been well-studied due to the technical limitations of tonometry. PURPOSE: To measure PWV to the microcirculation using near-infrared spectroscopy (NIRS). METHODS: In 13 healthy-young subjects (23±3.8 years), pulse pressure waveforms were collected from the carotid and radial arteries (with topical force sensors) simultaneously with optical waveforms (measured with NIRS) on the medial forearm. To determine criterion validity, carotid-radial PWV (crPWV) was measured with a well validated TT after 10 minutes of supine rest and after recovery from an arterial occlusion, and the values were compared with a customized algorithm produced in MATLAB for wave detection. To assess construct validity, both macro (crPWV)- and micro (mPWV)- circulatory PWVs were measured before and after 5 minutes of arterial occlusion (250 mmHg). RESULTS: The customized algorithm demonstrated good criterion validity with TT and strongly correlated with TT values (r=0.99, p<0.01), and a t-test revealed no differences between the customized algorithm and TT (p=0.88). Regarding construct validity, the crPWV results aligned well with typical wave patterns reported in previous literature, and demonstrates values reach slower than baseline after 30 seconds of reperfusion (Δ -0.37±0.34 m/s, p=0.029), which represents a reaction to hyperemia. Furthermore, mPWV was slowest immediately after cuff release (Δ -0.63±0.48 m/s, p<0.01), which is well aligned with the vasodilatory response in the microcirculation to ischemia. These findings validate that the novel mPWV method assessed with NIRS measures the correct construct. CONCLUSIONS: Measuring PWV with NIRS represents a feasible assessment of microcirculatory PWV and may be useful for assessing microcirculatory dysfunction in clinical populations, such as individuals with peripheral vascular diseases. Supported by UNO GRACA Grant