Limb and skeletal muscle blood flow measurements at rest and during exercise in human subjects

Abstract

Abbreviations: ∆f, Doppler frequency shift that occurs as transmitted sound waves of a specific frequency f are reflected by erythrocytes; ICG, indo-cyanine green; NIRS, near i.r. spectroscopy; PET, positron emission tomography. The aim of the present review is to present techniques used for measuring blood flow in human subjects and advice as to when they may be applicable. Since blood flow is required to estimate substrate fluxes, energy turnover and metabolic rate of skeletal muscle, accurate measurements of blood flow are of extreme importance. Several techniques have therefore been developed to enable estimates to be made of the arterial inflow to, venous outflow from, or local blood flow within the muscle. Regional measurements have been performed using electromagnetic flow meters, plethysmography, indicator methods (e.g. thermodilution and indo-cyanine green dye infusion), ultrasound Doppler, and magnetic resonance velocity imaging. Local estimates have been made using 133 Xe clearance, microdialysis, near i.r. spectroscopy, positron emission tomography and laser Doppler. In principle, the aim of the study, the type of interventions and the limitations of each technique determine which method may be most appropriate. Ultrasound Doppler and continuous indo-cyanine green dye infusion gives the most accurate limb blood flow measurements at rest. Moreover, the ultrasound Doppler is unique, as it does not demand a steadystate, and because its high temporal resolution allows detection of normal physiological variations as well as continuous measurements during transitional states such as at onset of and in recovery from exercise. During steady-state exercise thermodilution can be used in addition to indo-cyanine green dye infusion and ultrasound Doppler, where the latter is restricted to exercise modes with a fixed vessel position. Magnetic resonance velocity imaging may in addition be used to determine blood flow within deep single vessels. Positron emission tomography seems to be the most promising tool for local skeletal muscle blood-flow measurements in relation to metabolic activity, although the mode and intensity of exercise will be restricted by the apparatus design.

Hybrid diffuse optical techniques for continuous hemodynamic measurement in gastrocnemius during plantar flexion exercise

“…For example, baseline BF values observed by NIRS and SGVP with the VO protocol in this study (0.88 AE 0.4 and 1.13 AE 0.6 ml∕100 ml∕ min) fell in the range of 0.7 to 4.0 ml∕100 ml tissue∕ min, reported in the literature. 4,5,13,21,[51][52][53] The large variations observed in different studies may be due to the differences in populations and methodologies (i.e., NIRS, 4,51,53 Doppler ultrasound, 13,21 Xeclearance, 52 SGVP 5 ). Similarly, baseline _ VO 2 values quantified Table 2 Group averaged BF, blood oxygen saturation (StO 2 ), oxygen consumption rate ( _ VO 2 ), mean arterial pressure (MAP), and heart rate (HR) before, during, and after exercise (n ¼ 10).…”

“…Invasive methods of monitoring local muscle hemodynamics all suffer the same weakness in that they are clinically more dangerous due to increasing the risk of infection, inducing some degree of stress in the patient, and being inapplicable for continuous monitoring during dynamic protocols. 21,22 Functional magnetic resonance imaging (MRI) and positron emission tomography (PET) stand out as effective methods for assessing tissue blood flow (BF) and oxygenation as well as having the additional capability of measuring crucial metabolic parameters such as phosphate metabolites. The weakness of these two technologies is their expense to employ.…”

“…PET is still reliant on the use of radioactive elements, and both require confinement to measurement tubes and limit the modalities of exercise that may be employed. 21,[23][24][25] The use of near-infrared (NIR) diffuse optical methods allows continuous, rapid, and noninvasive acquisition of local deep tissue hemodynamics. The optical window of tissue (600 to 950 nm) allows NIR source light to illuminate tissue several centimeters beneath the skin.…”

Time‐courses of perfusion and phosphocreatine in rat leg during low‐level exercise and recovery

“…Most information on muscle blood flow is derived from noninvasive measurements made at the level of larger arteries or from invasive measurements made at the capillary level (5,17). ASL techniques represent a substantial advancement in this field because they can provide noninvasive quantification of capillary-level perfusion (18 -21).…”

Detecção da contração muscular através da tomografia de impedância elétrica.

“…Moreover, blood flow continuously oscillates at rest, as an effect of the heart beat and blood pressure. During exercise these oscillations are even more pronounced, being also influenced by the intramuscular pressure variations [38]. [37].…”