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Changes in skeletal muscle oxygenation during exercise measured by near-infrared spectroscopy on ascent to altitude

Martin, DS; Levett, DZH; Mythen, M; Grocott, MPW; Caudwell Xtreme Everest Res Grp,; (2009) Changes in skeletal muscle oxygenation during exercise measured by near-infrared spectroscopy on ascent to altitude. CRIT CARE , 13 , Article S7. 10.1186/cc8005.

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Abstract

Introduction: We sought to quantify changes in skeletal muscle oxygenation during exercise using near-infrared spectroscopy (NIRS) in healthy volunteers ascending to high altitude.Methods: Using NIRS, skeletal muscle tissue oxygen saturation (StO(2)) was measured in the vastus lateralis of 24 subjects. Measurements were performed at sea level (SL; 75 m), at 3,500 m, on arrival at 5,300 m (5,300 m-a; days 15 to 17) and at 5,300 m again (5,300 m-b; days 69 to 71). Amongst the subjects, nine remained at 5,300 m whilst 14 climbed to a maximum of 8,848 m. Exercise was 3 minutes of unloaded cycling followed by an incremental ramp protocol to exhaustion. The absolute StO(2) at different stages of exercise along with the difference between StO(2) at stages and the rate of change in StO(2) were compared between altitudes. Resting peripheral oxygen saturation was recorded.Results: NIRS data achieving predefined quality criteria were available for 18 subjects at 75 m, 16 subjects at 3,500 m, 16 subjects on arrival at 5,300 m and 16 subjects on departure from 5,300 m. At SL, mean StO(2) declined from 74.4% at rest to 36.4% at maximal oxygen consumption (P < 0.0001) and then rose to 82.3% (P < 0.0001) 60 seconds after exercise had ceased. At 3,500 m-a and 5,300 m-b, the pattern was similar to SL but absolute values were approximately 15% lower at all stages. At 5,300 m-a, the resting StO(2) was similar to SL and the change in StO(2) at each exercise stage less marked. At 5,300 m-b, the rate of decline in StO(2) during exercise was more rapid than SL (P = 0.008); here the climbers had a smaller decline in StO(2) during exercise (41.0%) and a slower rate of desaturation (0.086%/second) than those who had remained at 5,300 m (62.9% and 0.127%/second) (P = 0.031 and P = 0.047, respectively).Conclusion: In most individuals, NIRS can be used to measure exercising skeletal muscle oxygenation in the field. During exercise the patterns of absolute oxygenation are broadly similar at altitude and SL. Following prolonged adaptation to altitude, the rate of muscle desaturation is more rapid than observed at SL but less so in those exposed to extreme hypoxia above 5,300 m.

Type:Article
Title:Changes in skeletal muscle oxygenation during exercise measured by near-infrared spectroscopy on ascent to altitude
DOI:10.1186/cc8005
Keywords:ACUTE MOUNTAIN-SICKNESS, BLOOD-FLOW, INCREMENTAL EXERCISE, TISSUE OXYGENATION, MUSCULAR EXERCISE, MAXIMAL EXERCISE, IMAGING DEVICE, HEART-FAILURE, HYPOXIA, EVEREST
UCL classification:UCL > School of Life and Medical Sciences > Faculty of Life Sciences > Biosciences (Division of) > Neuroscience, Physiology and Pharmacology
UCL > School of Life and Medical Sciences > Faculty of Medical Sciences > Surgery and Interventional Science (Division of) > Research Department of General Surgery
UCL > School of Life and Medical Sciences > Faculty of Population Health Sciences > Institute of Child Health > Department of Cardiorespiratory Sciences > ICH - Portex Anaesthesia

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