title: Reproducibility of NIRS assessment of muscle oxidative capacity in smokers with and without COPD.
abstract: Low muscle oxidative capacity contributes to exercise intolerance in chronic obstructive pulmonary disease (COPD). Near-infrared spectroscopy (NIRS) allows non-invasive determination of the muscle oxygen consumption (mV̇O2) recovery rate constant (k), which is proportional to oxidative capacity assuming two conditions are met: 1) exercise intensity is sufficient to fully-activate mitochondrial oxidative enzymes; 2) sufficient O2availability. We aimed to determine reproducibility (coefficient of variation, CV; intraclass correlation coefficient, ICC) of NIRS k assessment in the gastrocnemius of 64 participants with (FEV164±23%predicted) or without COPD (FEV198±14%predicted). 10-15s dynamic contractions preceded 6min of intermittent arterial occlusions (5-10s each, ∼250mmHg) for k measurement. k was lower (P<0.05) in COPD (1.43±0.4min-1; CV=9.8±5.9%, ICC=0.88) than controls (1.74±0.69min-1; CV=9.9±8.4%; ICC=0.93). Poor k reproducibility was more common when post-contraction mV̇O2and deoxygenation were low, suggesting insufficient exercise intensity for mitochondrial activation and/or the NIRS signal contained little light reflected from active muscle. The NIRS assessment was well tolerated and reproducible for muscle dysfunction evaluation in COPD.
authors.affiliation: Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care Physiology and Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA. Electronic address: aadami@labiomed.org.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Adami
authors.affiliation: Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care Physiology and Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA. Electronic address: rcao@labiomed.org.
authors.forename: Robert
authors.initials: R
authors.lastname: Cao
authors.affiliation: Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care Physiology and Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA. Electronic address: porszasz@ucla.edu.
authors.forename: Janos
authors.initials: J
authors.lastname: Porszasz
authors.affiliation: Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care Physiology and Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA. Electronic address: casaburi@ucla.edu.
authors.forename: Richard
authors.initials: R
authors.lastname: Casaburi
authors.affiliation: Rehabilitation Clinical Trials Center, Division of Respiratory and Critical Care Physiology and Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA. Electronic address: hrossiter@ucla.edu.
authors.forename: Harry B
authors.initials: HB
authors.lastname: Rossiter
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000378:metabolism*; D015203:Reproducibility of Results; D012907:Smoking / Q000378:metabolism*; D019265:Spectroscopy, Near-Infrared; D013147:Spirometry; D014029:Tobacco Use Disorder / Q000150:complications / Q000378:metabolism
chemical_list: D010100:Oxygen
keywords: Exercise intolerance; Kinetics; Mitochondria; Oxygen consumption; Quality-control; Skeletal muscle