title: The relationship between skeletal muscle oxygenation and systemic oxygen uptake during exercise in subjects with COPD: a preliminary study.
abstract: BACKGROUND
  Muscle oxygenation correlates with systemic oxygen uptake (V(O₂)) in normal subjects; however, whether this relationship exists in COPD patients remains unclear. The purpose of this study was to investigate the influence of skeletal muscle oxygenation on V(O₂) during exercise in patients with COPD.
  
  
  METHODS
  Eight subjects performed an incremental cycle ergometer exercise test. We measured ventilation and pulmonary gas exchange with a metabolic measurement system. We also continuously monitored S(pO₂), and measured tissue oxygen saturation (S(tO₂)) in the vastus lateralis with continuous-wave near-infrared spectroscopy. We calculated the muscle oxygen extraction rate (MOER) based on S(pO₂) and S(tO₂). In addition, we calculated Pearson correlation coefficients to examine the relationships between the V(O₂) obtained during exercise testing and the mean values of S(pO₂), S(tO₂), heart rate (HR), and MOER for each 30-second interval of the tests. Finally, we analyzed the relationships between the peak V(O₂) and the slopes of HR/V(O₂), S(pO₂)/V(O₂), S(tO₂)/V(O₂), and MOER/V(O₂).
  
  
  RESULTS
  With the increasing exercise intensity, many subjects showed a gradual decrease in S(tO₂) and S(pO₂), but a gradual increase in HR and MOER. V(O₂) was negatively correlated with S(tO₂) and S(pO₂), and was positively correlated with HR and MOER. However, peak V(O₂) was not correlated with any of the slopes.
  
  
  CONCLUSIONS
  V(O₂) is highly influenced by oxygen utilization in exercising muscles, as well as by blood oxygenation levels and cardiac function. However, the impact of skeletal muscle utilization during exercise on peak V(O₂) varied greatly among the subjects.
authors.affiliation: Department of Physical Therapy, Faculty of Health Science, Kio University, Koryo, Japan. k.tabira@kio.ac.jp
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Tabira
authors.forename: Jun
authors.initials: J
authors.lastname: Horie
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Fujii
authors.forename: Toshio
authors.initials: T
authors.lastname: Aida
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Ito
authors.forename: Takahiko
authors.initials: T
authors.lastname: Fukumoto
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Imagita
authors.forename: Hideki
authors.initials: H
authors.lastname: Ishihara
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D010108:Oxyhemoglobins / Q000378:metabolism; D029424:Pulmonary Disease, Chronic Obstructive / Q000378:metabolism* / Q000503:physiopathology; D011659:Pulmonary Gas Exchange; D012123:Pulmonary Ventilation; D019265:Spectroscopy, Near-Infrared
chemical_list: D010108:Oxyhemoglobins; D010100:Oxygen