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Ultrasound Doppler (ultrasound + doppler)

Distribution by Scientific Domains

Life Sciences	80%

Selected Abstracts

Non-invasive monitoring of muscle blood perfusion by photoplethysmography: evaluation of a new application

ACTA PHYSIOLOGICA, Issue 4 2005
M. Sandberg
Abstract Aim:, To evaluate a specially developed photoplethysmographic (PPG) technique, using green and near-infrared light sources, for simultaneous non-invasive monitoring of skin and muscle perfusion. Methods:, Evaluation was based on assessments of changes in blood perfusion to various provocations, such as post-exercise hyperaemia and hyperaemia following the application of liniment. The deep penetrating feature of PPG was investigated by measurement of optical radiation inside the muscle. Simultaneous measurements using ultrasound Doppler and the new PPG application were performed to elucidate differences between the two methods. Specific problems related to the influence of skin temperature on blood flow were highlightened, as well. Results:, Following static and dynamic contractions an immediate increase in muscle perfusion was shown, without increase in skin perfusion. Liniment application to the skin induced a rapid increase in skin perfusion, but not in muscle. Both similarities and differences in blood flow measured by Ultrasound Doppler and PPG were demonstrated. The radiant power measured inside the muscle, by use of an optical fibre, showed that the near-infrared light penetrates down to the vascular depth inside the muscle. Conclusions:, The results of this study indicate the potentiality of the method for non-invasive measurement of local muscle perfusion, although some considerations still have to be accounted for, such as influence of temperature on blood perfusion. [source]

Stroke volume decreases during mild dynamic and static exercise in supine humans

ACTA PHYSIOLOGICA, Issue 2 2009
M. Elstad
Abstract Aim:, The contributions of cardiac output (CO) and total peripheral resistance to changes in arterial blood pressure are debated and differ between dynamic and static exercise. We studied the role stroke volume (SV) has in mild supine exercise. Methods:, We investigated 10 healthy, supine volunteers by continuous measurement of heart rate (HR), mean arterial blood pressure, SV (ultrasound Doppler) and femoral beat volume (ultrasound Doppler) during both dynamic mild leg exercise and static forearm exercise. This made it possible to study CO, femoral flow (FF) and both total and femoral peripheral resistance beat-by-beat. Results:, During a countdown period immediately prior to exercise, HR and mean arterial pressure increased, while SV decreased. During mild supine exercise, SV decreased by 5,8%, and most of this was explained by increased mean arterial pressure. Dynamic leg exercise doubled femoral beat volume, while static hand grip decreased femoral beat volume by 18%. FF is tightly regulated according to metabolic demand during both dynamic leg exercise and static forearm exercise. Conclusion:, Our three major findings are, firstly, that SV decreases during both dynamic and static mild supine exercise due to an increase in mean arterial pressure. Secondly, femoral beat volume decreases during static hand grip, but FF is unchanged due to the increase in HR. Finally, anticipatory responses to exercise are apparent prior to both dynamic and static exercise. SV changes contribute to CO changes and should be included in studies of central haemodynamics during exercise. [source]

Non-invasive monitoring of muscle blood perfusion by photoplethysmography: evaluation of a new application

Effect of Angular Error on Tissue Doppler Velocities and Strain

ECHOCARDIOGRAPHY, Issue 7 2003
Camilla Storaa M.S.
One of the major criticisms of ultrasound Doppler is its angle dependency, that is its ability to measure velocity components directly to or from the transducer only. The present article aims to investigate the impact of this angular error in a clinical setting. Apical two- and four-chamber views were recorded in 43 individuals, and the myocardium was marked by hand in each image. We assume that the main direction of the myocardial velocities is longitudinal and correct for the angular error by backprojecting measured velocities onto the longitudinal direction drawn. Strain was calculated from both corrected and uncorrected velocities in 12 segments for each individual. The results indicate that the difference between strain values calculated from corrected and uncorrected velocities is insignificant in 5 segments and within a decimal range in 11 segments. The biggest difference between measured and corrected strain values was found in the apical segments. Strain is also found to be more robust against angular error than velocities because the difference between corrected and uncorrected values is smaller for strain. Considering that there are multiple sources of noise in ultrasound Doppler measurements, the authors conclude that the angular error has so little impact on longitudinal strain that correction for this error can safely be omitted. (ECHOCARDIOGRAPHY, Volume 20, October 2003) [source]

Different vasodilator responses of human arms and legs

THE JOURNAL OF PHYSIOLOGY, Issue 3 2004
Sean C. Newcomer
Forearm vascular responses to intra-arterial infusions of endothelium-dependent and -independent vasodilators have been thoroughly characterized in humans. While the forearm is a well-established experimental model for studying human vascular function, it is of limited consequence to systemic cardiovascular control owing to its small muscle mass and blood flow requirements. In the present study we determined whether these responses could be generalized to the leg. Based upon blood pressure differences between the leg and arm during upright posture, we hypothesized that the responsiveness to endothelium-dependent vasodilators would be greater in the forearm than the leg. Brachial and femoral artery blood flow (Q, ultrasound Doppler) at rest and during intra-arterial infusions of endothelium-dependent (acetylcholine and substance P) and -independent (sodium nitroprusside) vasodilators were measured in eight healthy men (22,27 years old). Resting blood flows in the forearm before infusion of acetylcholine, substance P or sodium nitroprusside were 25 ± 4, 30 ± 7 and 29 ± 5 ml min,1, respectively, and in the leg were 370 ± 32, 409 ± 62 and 330 ± 30 ml min,1, respectively. At the highest infusion rate of acetylcholine (16 ,g (100 ml tissue),1 min,1) there was a greater (P < 0.05) increase in Q to the forearm (1864 ± 476%) than to the leg (569 ± 86%). Similarly, at the highest infusion rate of substance P (125 pg (100 ml tissue),1 min,1) there was a greater (P < 0.05) increase in Q to the forearm (911 ± 286%) than to the leg (243 ± 58%). The responses to sodium nitroprusside (1 ,g (100 ml tissue),1 min,1) were also greater (P < 0.05) in the forearm (925 ± 164%) than in the leg (326 ± 65%). These data indicate that vascular responses to both endothelium-dependent and -independent vasodilator agents are blunted in the leg compared to the forearm. [source]