Performance of near-infrared spectroscopy in measuring local O 2 consumption and blood flow in skeletal muscle MIREILLE C. P. VAN BEEKVELT, 1,2 WILLY N. J. M. COLIER, 1 RON A. WEVERS, 2 AND BAZIEL G. M. VAN ENGELEN 2 1 Department of Physiology, Faculty of Medical Sciences, University of Nijmegen, and 2 Neuromuscular Centre Nijmegen, Institute of Neurology, University Medical Centre St. Radboud, 6500 HB Nijmegen, The Netherlands Received 3 April 2000; accepted in final form 1 September 2000 Van Beekvelt, Mireille C. P., Willy N. J. M. Colier, Ron A. Wevers, and Baziel G. M. van Engelen. Perfor- mance of near-infrared spectroscopy in measuring local O 2 consumption and blood flow in skeletal muscle. J Appl Physiol 90: 511–519, 2001.—The aim of this study was to investigate local muscle O 2 consumption (muscV ˙ O 2 ) and fore- arm blood flow (FBF) in resting and exercising muscle by use of near-infrared spectroscopy (NIRS) and to compare the results with the global muscV ˙ O 2 and FBF derived from the well-established Fick method and plethysmography. muscV ˙ O 2 was derived from 1) NIRS using venous occlusion, 2) NIRS using arterial occlusion, and 3) the Fick method [muscV ˙ O 2(Fick) ]. FBF was derived from 1) NIRS and 2) strain- gauge plethysmography. Twenty-six healthy subjects were tested at rest and during sustained isometric handgrip exer- cise. Local variations were investigated with two indepen- dent and simultaneously operating NIRS systems at two different muscles and two measurement depths. muscV ˙ O 2 increased more than fivefold in the active flexor digitorum superficialis muscle, and it increased 1.6 times in the brachi- oradialis muscle. The average increase in muscV ˙ O 2(Fick) was twofold. FBF increased 1.4 times independent of the muscle or the method. It is concluded that NIRS is an appropriate tool to provide information about local muscV ˙ O 2 and local FBF because both place and depth of the NIRS measure- ments reveal local differences that are not detectable by the more established, but also more global, Fick method. muscle metabolism; forearm blood flow; noninvasive; sus- tained isometric handgrip exercise NEAR-INFRARED SPECTROSCOPY (NIRS) is a noninvasive, continuous, and direct method to determine oxygen- ation and hemodynamics in tissue. It enables the study of local differences in muscle O 2 consumption (muscV ˙ O 2 ) and delivery. NIRS has also shown to be a sensitive tool in the discrimination between normal and pathological states. Abnormal oxygenation due to insufficient delivery has been found with NIRS in patients with heart failure (4, 29, 30, 44) and periph- eral vascular disease (6, 23, 24, 32). NIRS was also used to characterize patients with metabolic myopa- thies, in which abnormalities in oxygenation pattern are related to O 2 extraction instead of O 2 delivery (1, 2, 17). Our recent study showed that NIRS makes it possible to quantify differences in O 2 consumption and forearm blood flow (FBF) at rest as well as during exercise and discriminates between patients with mitochondrial myopathies and healthy persons (39). Quantification of muscV ˙ O 2 and blood flow using NIRS has become possible by incorporating a differen- tial path-length factor (DPF) in the Lambert-Beer law (8) and applying an occlusion to control circulation in the limb. muscV ˙ O 2 has been measured with NIRS dur- ing arterial occlusion (6, 7, 9, 10, 38) as well as during venous occlusion (9, 11, 19, 38). Muscle blood flow has been measured with NIRS during venous occlusion (11, 38) and by use of an intravascular tracer (14). Comparison of the NIRS method to quantify blood flow with more established methods has been reported in only a few studies. NIRS blood flow measurement during rest, obtained by an intravascular tracer, was compared with venous occlusion plethysmography by Edwards et al. (14), and De Blasi et al. (11) compared NIRS flow measurement with plethysmographic flow measurement, both simultaneously measured during venous occlusion. Quantitative NIRS muscV ˙ O 2 mea- surement, however, has never been compared with a more established method. Although Homma et al. (19) showed that there was a relationship between the deoxygenation pattern estimated by NIRS during ve- nous occlusion and the O 2 consumption obtained by a more established method, they did not calculate quan- titative values for muscV ˙ O 2 . The present study was undertaken to determine whether quantitative measurements of NIRS muscV ˙ O 2 and FBF of human skeletal muscle at rest as well as during exercise correlates with the more established methods of combining blood gas analysis, pulse oxim- etry, and plethysmography and whether the depth and the place of the NIRS measurements reveal local dif- ferences that are not detectable by the more estab- lished, though global, Fick method. Address for reprint requests and other correspondence: M. C. P. van Beekvelt, Neuromuscular Centre Nijmegen, Institute of Neurol- ogy, University Medical Centre St. Radboud, PO Box 9101, 6500 HB Nijmegen, The Netherlands (E-mail: M.vanBeekvelt@czzoknf.azn.nl). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked ‘‘advertisement’’ in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 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