title: Noninvasive estimation of oxygen consumption in human calf muscle through combined NMR measurements of ASL perfusion and T₂ oxymetry.
abstract: The objective of this work was to demonstrate the feasibility of measuring muscle O2 consumption (V˙O2) noninvasively with a combination of functional nuclear magnetic resonance (NMR) imaging methods, and to verify that changes in muscle V˙O2 can be detected with a temporal resolution compatible with physiological investigation and patient ease. T2-based oxymetry of arterial and venous blood was combined with the arterial-spin labeling (ASL)-based determination of muscle perfusion. These measurements were performed on 8 healthy volunteers under normoxic and hypoxic conditions in order to assess the sensitivity of measurements over a range of saturation values. Blood samples were drawn simultaneously and used to titrate blood T2 measurements versus hemoglobin O2 saturation (%HbO2) in vitro. The in vitro calibration curve of blood T2 fitted very well with the %HbO2 (r(2): 0.95). The in vivo venous T2 measurements agreed well with the in vitro measurements (intraclass correlation coefficient 0.82, 95% confidence interval 0.61-0.91). Oxygen extraction at rest decreased in the calf muscles subjected to hypoxia (p = 0.031). The combination of unaltered muscle perfusion and pinched arteriovenous O2 difference (p = 0.038) pointed towards a reduced calf muscle V˙O2 during transient hypoxia (p = 0.018). The results of this pilot study confirmed that muscle O2 extraction and V˙O2 can be estimated noninvasively using a combination of functional NMR techniques. Further studies are needed to confirm the usefulness in a larger sample of volunteers and patients.
authors.affiliation: Institute of Myology, Paris, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Decorte
authors.forename: Tania
authors.initials: T
authors.lastname: Buehler
authors.forename: Ericky
authors.initials: E
authors.lastname: Caldas de Almeida Araujo
authors.forename: Alexandre
authors.initials: A
authors.lastname: Vignaud
authors.forename: Pierre G
authors.initials: PG
authors.lastname: Carlier
mesh_terms: D000328:Adult; D002138:Calibration; D005240:Feasibility Studies; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000503:physiopathology; D007866:Leg; D008279:Magnetic Resonance Imaging / Q000592:standards; D008297:Male; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000378:metabolism*; D010092:Oximetry / Q000592:standards; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D055420:Perfusion Imaging / Q000379:methods* / Q000592:standards; D010865:Pilot Projects; D011237:Predictive Value of Tests; D012015:Reference Standards; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D010100:Oxygen