title: Microvascular tissue oxygenation and oxidative metabolism changes in the pedicled latissimus dorsi muscle during graded hypoxia: correlation between near infrared and 31P nuclear magnetic resonance spectroscopy.
abstract: BACKGROUND
  In this study, the microvascular tissue oxygenation and oxidative muscle metabolism during graded hypoxia and reoxygenation were examined in a rabbit model by near-infrared (NIR) spectroscopy and correlated with high-energy phosphates measured by (31)P nuclear magnetic resonance (NMR) spectroscopy.
  
  
  METHODS
  Graded hypoxia was performed in a New Zealand rabbit model (n = 20, 2.0 ± 0.4 kg) by a stepwise reduction of the fraction of inspired oxygen (FiO(2)) from 0.3 to 0.05 (intervention group versus control group). Recovery and reoxygenation were achieved using FiO(2) of 0.3. A noninvasive NIR spectroscopy sensor and NMR probe was positioned on the surface of the prepared pedicled latissimus dorsi muscle. Microvascular tissue oxygenation (oxyhemoglobin, HbO(2); deoxyhemoglobin, HHb) and redox state of cytochrome oxidase (CytOx) were measured by NIR spectroscopy and correlated with standard values of oxidative muscle metabolism (phosphocreatine, PCr; adenosine triphosphate, ATP) measured by time-resolved (31)P NMR spectroscopy (4.7T).
  
  
  RESULTS
  Significant correlation was found between PCr and HbO(2) (r = 0.85, P < 0.001) and HHb (r = -0.75, P < 0.001). β-ATP levels correlated significantly with CytOx (r = 0.87, P < 0.001).
  
  
  CONCLUSIONS
  The data suggest that changes in high-energy phosphates (PCr- and ATP-levels) correlate closely with microvascular tissue oxygenation (HbO(2), HHb, CytOx) measured by NIR spectroscopy.
authors.affiliation: Biomedical Research Center, Cardiovascular Research Lab, Department of Cardiac and Thoracic Vascular Surgery, University Medical Center, Philipps-University of Marburg/Lahn, Marburg/Lahn, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Troitzsch
authors.forename: Rainer
authors.initials: R
authors.lastname: Moosdorf
authors.forename: Sebastian
authors.initials: S
authors.lastname: Vogt
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D003576:Electron Transport Complex IV / Q000378:metabolism; D006454:Hemoglobins / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D055806:Microvessels / Q000378:metabolism*; D023421:Models, Animal; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010108:Oxyhemoglobins / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D010759:Phosphorus Isotopes; D011817:Rabbits; D019265:Spectroscopy, Near-Infrared / Q000379:methods*
chemical_list: D006454:Hemoglobins; D010108:Oxyhemoglobins; D010759:Phosphorus Isotopes; D010725:Phosphocreatine; D000255:Adenosine Triphosphate; C100003:deoxyhemoglobin; D003576:Electron Transport Complex IV; D010100:Oxygen