Characterization and reproducibility of forearm arterial flow during reactive hyperemia.

Peripheral arterial flow has been assessed for a variety of indications including characterization of endothelial function during reactive hyperemia. However, quantification of this blood flow as a surrogate remains an imperfect reflection of endothelial function. We sought to better characterize hyperemic reaction to (1) elucidate the influence of the endothelial function and (2) assess the reproducibility of our modeling over time. Sixteen normal subjects underwent simultaneous forearm reactive hyperemia testing with a near-infrared system at baseline, baseline +24 h and baseline +27 h. Baseline flow was measured to 3.6 +/- 0.2 ml dl(-1) min(-1), and was highly reproducible 24 and 27 h later. With reactive hyperemia, the blood flow increased to 20.5 +/- 4.6 ml dl(-1) min(-1). Arterial blood flow curves during reactive hyperemia displayed a bimodal pattern, with the second peak occurring 59.1 +/- 10.6 s after the onset of hyperemia. We believe that this latest peak represents the contribution of endothelial factors to the hyperemic reaction. Modeling of hyperemic curves led to the introduction of a reproducible new parameter (etafactor) that reflects the normalized contribution of this second peak. In conclusion, forearm arterial flow during reactive hyperemia revealed a bimodal distribution where functional interpretation allowed distinction of the two components. Basal flow measurements and results of this modeling were reproducible 24 and 27 h later.

Arterial flow measurements during reactive hyperemia using NIRS.

Non-invasive evaluation of peripheral perfusion may be useful in many contexts including clinical research. We validated a novel non-invasive spectroscopy technique to quantify forearm arterial inflow. This method, which is based on the measurement of tissular total hemoglobin variations after an ischemic period, was compared to strain gauge plethysmography (SGP). The technique uses near-infrared spectroscopy (NIRS) to determine the rate of change of forearm tissue oxygenation during reactive hyperemia. In this study, 13 subjects were simultaneously evaluated with NIRS and SGP. Nine baseline flow measurements were performed to assess the reproducibility of each method. Twenty-seven serial measurements were then made to evaluate flow variation during forearm reactive hyperemia. SGP and NIRS methods showed excellent reproducibility with the same intra-class correlation coefficients (0.98). In conclusion, the NIRS technique appears well suited for non-invasive evaluation of quantitative arterial forearm flow.

Near-infrared spectroscopy to monitor peripheral blood flow perfusion.

BACKGROUND: Non-invasive evaluation of peripheral perfusion may be useful in many contexts including peri-operative monitoring. We validated a novel non-invasive spectroscopy technique to assess peripheral perfusion. This method, which is based on the measurement of tissue saturation variations after an ischemic period, was compared to strain gauge plethysmography and radionuclide plethysmography. The technique uses near-infrared spectroscopy (NIRS) to determine the rate of change of forearm tissue saturation during reactive hyperemia. METHODS: In a prospective crossover study, 25 subjects were simultaneously evaluated with NIRS and strain gauge plethysmography. Six baseline flow measurements were performed to assess the reproducibility of each method. Twenty-seven serial measurements were then made to evaluate flow variation during forearm reactive hyperemia. RESULTS: Strain gauge and NIRS methods showed excellent reproducibility with intra-class correlation coefficients of 0.96 and 0.93, respectively. CONCLUSION: The NIRS technique appears well suited for the non-invasive evaluation of limb perfusion.

Mobile detection system to evaluate reactive hyperemia using radionuclide plethysmography.

We validated a novel mobile detection system to evaluate reactive hyperemia using the radionuclide plethysmography technique. Twenty-six subjects underwent simultaneously radionuclide plethysmography with strain gauge plethysmography. Strain gauge and radionuclide methods showed excellent reproducibility with intraclass correlation coefficients of 0.96 and 0.89 respectively. There was also a good correlation of flows between the two methods during reactive hyperemia (r = 0.87). We conclude that radionuclide plethysmography using this mobile detection system is a non-invasive alternative to assess forearm blood flow and its dynamic variations during reactive hyperemia.

SPECT versus planar gated blood pool imaging for left ventricular evaluation.

BACKGROUND: We developed a new segmentation algorithm based on the invariance of the Laplacian (IL) to compute volumes and ejection fractions and compared these results with planar analysis and gradients by use of a standard algorithm (QBS). METHODS AND RESULTS: Planar and single photon emission computed tomography blood pool acquisition was performed in 202 patients. Planar left ventricular ejection fraction (LVEF) was used as the gold standard, and single photon emission computed tomography images were processed by both 3-dimensional (3D) methods. Correlations between each 3D algorithm and planar methodology were as follows: r = 0.77 for QBS and r = 0.84 for IL. Mean LVEFs were 32.72% +/- 13.05% for the planar method, 32.32% +/- 15.98% for QBS, and 31.93% +/- 13.44% for IL (P = .16). Bland-Altman analysis closely demonstrated negligible systematic bias for both 3D methods. Standard errors of bias were comparable between methods (9.36% for QBS and 7.44% for IL, P = .48). Linear regression of the Bland-Altman bias revealed a slope significantly different from 0 for the QBS method (0.22 +/- 0.048, P < .0001) but not for IL (-0.032 +/- 0.0044, P = .47). CONCLUSION: The new segmentation algorithm provides comparable results to QBS and planar analysis. However, with QBS, the difference in LVEF was correlated with the magnitude of LVEF, which was not found with the new algorithm.