title: Dynamics of microvascular oxygen partial pressure in contracting skeletal muscle of rats with chronic heart failure.
abstract: OBJECTIVE
  This investigation tested the hypothesis that the dynamics of muscle microvascular O(2) pressure (PO(2)m, which reflects the ratio of O(2) utilization [V*O(2)] to O(2) delivery [Q*O(2)]) following the onset of contractions would be altered in chronic heart failure (CHF).
  
  
  METHODS
  Female Sprague-Dawley rats were subjected to a myocardial infarction (MI) or a sham operation (Sham). Six to 10 weeks post Sham (n=6) or MI (n=17), phosphorescence quenching techniques were utilized to determine PO(2)m dynamics at the onset of spinotrapezius muscle contractions (1 Hz).
  
  
  RESULTS
  MI rats were separated into groups with Moderate (n=10) and Severe (n=7) CHF based upon the degree of left ventricular (LV) dysfunction as indicated by structural abnormalities (increased right ventricle weight and lung weight normalized to body weight). LV end-diastolic pressure was elevated significantly in both CHF groups compared with Sham (Sham, 3+/-1; Moderate CHF, 9+/-2; Severe CHF, 27+/-4 mmHg, P<0.05). The PO(2)m response was modeled using time delay and exponential components to fit the PO(2)m response to the steady-state. Compared with Shams, the time constant (tau) of the primary PO(2)m response was significantly speeded in Moderate CHF (tau, Sham, 19.0+/-1.5; Moderate CHF, 13.2+/-1.9 s, P<0.05) and slowed in Severe CHF (tau, 28.2+/-3.4 s, P<0.05). Within the Severe CHF group, tau increased linearly with the product of right ventricular and lung weight (r=0.83, P<0.05).
  
  
  CONCLUSIONS
  These results suggest that CHF alters the dynamic matching of muscle V*O(2)-to-Q*O(2) across the transition from rest to contractions and that the nature of that perturbation is dependent upon the severity of cardiac dysfunction.
authors.affiliation: Departments of Kinesiology, Anatomy and Physiology, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: E R
authors.initials: ER
authors.lastname: Diederich
authors.forename: B J
authors.initials: BJ
authors.lastname: Behnke
authors.forename: P
authors.initials: P
authors.lastname: McDonough
authors.forename: C A
authors.initials: CA
authors.lastname: Kindig
authors.forename: T J
authors.initials: TJ
authors.lastname: Barstow
authors.forename: D C
authors.initials: DC
authors.lastname: Poole
authors.forename: T I
authors.initials: TI
authors.lastname: Musch
mesh_terms: D000818:Animals; D005260:Female; D006333:Heart Failure / Q000097:blood / Q000209:etiology / Q000503:physiopathology*; D008833:Microcirculation; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000098:blood supply*; D009203:Myocardial Infarction / Q000150:complications; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D010313:Partial Pressure; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D010100:Oxygen