Metabolism and aerobic capacity of skeletal muscle in chronic respiratory failure related to chronic obstructive pulmonary disease.
The calf muscle energy metabolism of 8 stable chronic obstructive pulmonary disease (COPD) patients with chronic respiratory failure (arterial oxygen tension (Pao2) 7.7 +/- 0.4 kPa or 58 +/- 3 mmHg) was studied, using 31-phosphorus magnetic resonance spectroscopy (31P MRS). MRS spectra were acquired at rest and during the course of 360 pedal movements at 20, 35 and 50% of the maximal voluntary contraction (MVC) and during recovery. Eight healthy age-matched subjects served as the control group. No significant differences between groups were observed in resting muscle, as regards intracellular pH, Pi/PCr ratio (Pi: inorganic phosphate; PCr: phosphocreatine) and the relative ATP expressed as the ratio beta ATP/PCr + Pi + PME (PME: phosphomonoester). Although effective power outputs were similar for both groups at each work level, COPD patients exhibited a higher Pi/PCr ratio than health controls (3.34 +/- 0.89 vs 0.49 +/- 0.05 at 50% MVC; p less than 0.01) and a lower pHi (6.65 +/- 0.11 vs 7.06 +/- 0.02 at 50% MVC; p less than 0.01). PCr resynthesis during recovery was slower in patients than in control subjects (t1/2 PCr 1.27 +/- 0.26 min vs 0.47 +/- 0.05 min; p less than 0.05). These results suggest impairment of aerobic capacity in a non-ventilatory working muscle, which may be due to hypoxaemia in patients with chronic respiratory failure.
Wuyam
B
B
Dept. of Respiratory Medicine, CHU Grenoble, France.
Payen
J F
JF
Levy
P
P
Bensaïdane
H
H
Reutenauer
H
H
Le Bas
J F
JF
Benabid
A L
AL
D000368:Aged; D000886:Anthropometry; D004734:Energy Metabolism; D015444:Exercise; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D008173:Lung Diseases, Obstructive / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008875:Middle Aged; D009119:Muscle Contraction; D009132:Muscles / Q000378:metabolism*; D010710:Phosphates / Q000032:analysis; D012129:Respiratory Function Tests; D012131:Respiratory Insufficiency / Q000378:metabolism*
D010710:Phosphates