Blood flow monitoring during rhythm exercising is very
important for sports medicine and muscle dieases. Diffuse correlation
spectroscopy(DCS) is a relative new invasive way to monitor blood flow
but suffering from muscle fiber motion. In this study we focus on how to
remove exercise driven artifacts and obtain accurate estimates of the
increase in blood flow from exercise. Using a novel fast software correlator,
we measured blood flow in forearm flexor muscles of N=2 healthy adults
during handgrip exercise, at a sampling rate of 20 Hz. Combining the blood
flow and acceleration data, we resolved the motion artifact in the DCS
signal induced by muscle fiber motion, and isolated the blood flow
component of the signal from the motion artifact. The results show that
muscle fiber motion strongly affects the DCS signal, and if not accounted
for, will result in an overestimate of blood flow more than ~1000%. Our
measurements indicate rapid dilation of arterioles following exercise onset,
which enabled blood flow to increase to a plateau of ~200% in ~10s. The
blood flow also rapidly recovered to baseline following exercise in ~10s.
Finally, preliminary results on the dependence of blood flow from exercise
intensity changes will be discussed.
We investigate and assess the utility of a simple scheme for continuous absolute blood flow monitoring based on diffuse correlation spectroscopy (DCS). The scheme calibrates DCS using venous-occlusion diffuse optical spectroscopy (VO-DOS) measurements of arm muscle tissue at a single time-point. A calibration coefficient (γ) for the arm is determined, permitting conversion of DCS blood flow indices to absolute blood flow units, and a study of healthy adults (N=10) is carried out to ascertain the variability of γ. The average DCS calibration coefficient for the right (i.e., dominant) arm was γ=(1.24±0.15)×108 (mL·100 mL−1·min−1)/(cm2/s). However, variability can be significant and is apparent in our site-to-site and day-to-day repeated measurements. The peak hyperemic blood flow overshoot relative to baseline resting flow was also studied following arm-cuff ischemia; excellent agreement between VO-DOS and DCS was found (R2=0.95, slope=0.94±0.07, mean difference=−0.10±0.45). Finally, we show that incorporation of subject-specific absolute optical properties significantly improves blood flow calibration accuracy.