Reliability of laser Doppler, near-infrared spectroscopy and Doppler ultrasound for peripheral blood flow measurements during and after exercise in the heat

The famous British scientist Sir Cyril A. Clarke in 1975 wrote the introduction for a new book, Arteries and Veins , with the following words: . . . In spite of all advances, mortality remains a steady 100 per cent and it is disorders of the arteries and veins which claim the majority of us. we sclerose, we clot, arrhythmias hit us, or our tubing wears out. By way of consolation, however, more of us now go the way of all flesh properly diagnosed and there are many ways of cheating the ancient enemy. . . . Clark at the time did not realize what advances were ahead of him, and the book he introduced with these dark lines included a chapter by R.G. Gosling and D.H. King which described a new promising technique of ultrasound angiography. Cyril Clark himself died at the age of 93! Blood flow measurements during resting conditions fail to detect any reduction of volume flow in patients with occlusive vascular disease, therefore for quantitative evaluation of the functional capacity of the peripheral circulation various functional tests implying increased circulatory demands needed to be introduced. The most useful clinical information could be obtained from peak-flow values after a period of obstruction and exercise followed by volume plethysmographic measurements of blood flow. Olav Thulesius introduced a foot ergometer in 1963 which allowed detection of maximal blood flow after graded muscular exercise. Its use was complicated and time-consuming when applied in conjunction with blood flow measurements with a water-filled volume plethysmograph. Therefore a faster and easier method for determination of peripheral blood flow was desirable. In 1967, the ultrasound scanning method for the detection of arterial blood flow signals in the diagnosis of fetal life during pregnancy was introduced in Sweden. This same principle became the method for detecting blood flow in peripheral blood vessels. The method used was a hand-held instrument which included two piezoelectric elements, one to transmit ultrasound signals and the other to receive the returning echoes back-scattered from the blood vessels. The instrument used for the detection of peripheral blood flow was the same as that for the detection of the fetal blood flow in pregnancy.

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Tissue Oxygenation by Near-Infrared Spectroscopy and Muscle Blood Flow During Isometric Contractions of the Forearm

Canadian Journal of Applied Physiology ◽

10.1139/h99-018 ◽

1999 ◽

Vol 24 (3) ◽

pp. 216-230 ◽

Cited By ~ 38

Author(s):

Andrew Hicks ◽

Stuart Mcgill ◽

Richard L. Hughson

Keyword(s):

Blood Flow ◽

Infrared Spectroscopy ◽

Doppler Ultrasound ◽

Near Infrared Spectroscopy ◽

Near Infrared ◽

Tissue Oxygenation ◽

Muscle Blood Flow ◽

Venous Blood ◽

Muscle Oxygenation ◽

Isometric Contractions

The relationship between tissue oxygenation measured by near-infrared spectroscopy (NIRS) and forearm muscle blood flow (FBF) measured by Doppler ultrasound was tested during isometric contractions at 10 and 30% maximal voluntary contraction (MVC) under conditions of normoxia and hypoxia (14% inspired O2). Six subjects maintained contractions at 10% MVCfor 5 min and at 30% for 2 min in both gas conditions. FBF was elevated during exercise at 10% MVC in hypoxia compared to normoxia, but there was no further increase in flow at 30% MVC. Median power frequency calculations from electromyographic recordings suggested progressive development of fatigue throughout both 10 and 30% MVC contractions. NIRS indicated no change in muscle oxygenation at 10% MVC, but deep venous blood O2 saturation was reduced in normoxia and more so in hypoxia. At 30% MVC, both NIRS and venous O2 saturation were reduced, with no effect of hypoxia on the NIRS signal. While NIRS might provide an indication of muscle oxygenation during isometric exercise, the conflicting findings for NIRS and direct venous blood sampling at 10 vs. 30% MVC suggest caution in the application of this noninvasive technique. Key words: exercise, Doppler ultrasound, venous blood. O2 saturation, hemoglobin

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Renovascular reactivity measured by near-infrared spectroscopy

Journal of Applied Physiology ◽

10.1152/japplphysiol.00024.2012 ◽

2012 ◽

Vol 113 (2) ◽

pp. 307-314 ◽

Cited By ~ 36

Author(s):

Christopher J. Rhee ◽

Kathleen K. Kibler ◽

R. Blaine Easley ◽

Dean B. Andropoulos ◽

Marek Czosnyka ◽

...

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Infrared Spectroscopy ◽

Hemorrhagic Shock ◽

Renal Blood Flow ◽

Arterial Blood Pressure ◽

Near Infrared Spectroscopy ◽

Near Infrared ◽

Laser Doppler ◽

Arterial Blood

Hypotension and shock are risk factors for death, renal insufficiency, and stroke in preterm neonates. Goal-directed neonatal hemodynamic management lacks end-organ monitoring strategies to assess the adequacy of perfusion. Our aim is to develop a clinically viable, continuous metric of renovascular reactivity to gauge renal perfusion during shock. We present the renovascular reactivity index (RVx), which quantifies passivity of renal blood volume to spontaneous changes in arterial blood pressure. We tested the ability of the RVx to detect reductions in renal blood flow. Hemorrhagic shock was induced in 10 piglets. The RVx was monitored as a correlation between slow waves of arterial blood pressure and relative total hemoglobin (rTHb) obtained with reflectance near-infrared spectroscopy (NIRS) over the kidney. The RVx was compared with laser-Doppler measurements of red blood cell flux, and renal laser-Doppler measurements were compared with cerebral laser-Doppler measurements. Renal blood flow decreased to 75%, 50%, and 25% of baseline at perfusion pressures of 60, 45, and 40 mmHg, respectively, whereas in the brain these decrements occurred at pressures of 30, 25, and 15 mmHg, respectively. The RVx compared favorably to the renal laser-Doppler data. Areas under the receiver operator characteristic curves using renal blood flow thresholds of 50% and 25% of baseline were 0.85 (95% CI, 0.83–0.87) and 0.90 (95% CI, 0.88–0.92). Renovascular autoregulation can be monitored and is impaired in advance of cerebrovascular autoregulation during hemorrhagic shock.

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