TITLE:
Measurement of the exercising blood flow during rhythmical muscle contractions assessed by Doppler ultrasound: Methodological considerations
AUTHORS:
Takuya Osada, Bengt Saltin, Stefan P. Mortensen, Goran Rådegran
KEYWORDS:
Exercising Blood Flow; Doppler Ultrasound; Muscle Contraction; Physiological Flow Variations
JOURNAL NAME:
Journal of Biomedical Science and Engineering,
Vol.5 No.12A,
December
31,
2012
ABSTRACT:
Given
the recent technological developments, ultra-sound Doppler can provide
valuable measurements of arterial blood flow with high temporal resolution. In a
clinical setting, measurements of hemodynamics is used to monitor, diagnose and
manage changes in blood velocity profile for cardiac valve disease, relatively
large vessel stenosis and other cardiovascular diseases. In health science and
preventive medicine for cardiovascular disease with exercise therapy,
evaluation of cardiac and vascular function is a useful indicator not only at
rest but also during exercise, leading to improved exercise tolerance as well
as physical activity. During exercise, the increase in oxygen uptake
(calculated as product of arterial blood flow to the exercising limb and the
arteriovenous oxygen difference) is directly proportional to the work
performed. The increased oxygen demand is met through a central mechanism, an
increase in cardiac output and blood pressure, as well as a peripheral
mechanism, an increase in vascular conductance and oxygen extraction (major
part in the whole exercising muscles) from the blood. Therefore, the determination
of the local blood flow dynamics (potential oxygen supply) feeding to rhythmic
muscle contractions can contribute to the understanding of the factors
limiting the work capacity including, for instance the muscle metabolism,
substance utilization and vasodilatation in the exercising muscle. Using non-invasive
measures of pulsed Doppler ultrasound the validity of evaluating blood
velocity/flow in the fore- arm or lower limb conduit artery feeding to the mus-
cle is demonstrated during rhythmic muscle exercise; however the exercising
blood velocity profile (fast Fourier transformation) due to muscle contractions
is
always seen as a physiological variability or fluctuations in the magnitude in blood velocity due to the spontaneous muscle
contraction and relaxation induced changes in force curve intensity.
Considering the above mentioned variation in blood velocity in relation to
muscle contractions may provide valuable information for evaluating the blood
flow dynamics during exercise. This review presents the methodological
concept that underlines the
methodological considerations for determining the exercising blood
velocity/flow in the limb conduit artery in relation
the exercise model of dynamic leg exercise assessed by pulsed Doppler
ultrasonography.