COPD patients with chronic respiratory failure exhibited a higher Pi/PCr ratio (3.34 vs 0.49; p<0.01) and lower intracellular pH (6.65 vs 7.06; p<0.01) during exercise compared to healthy controls.
Case-Control (n=16)
Does calf muscle energy metabolism during exercise and recovery differ between COPD patients with chronic respiratory failure and healthy controls?
COPD patients with chronic respiratory failure show impaired aerobic capacity in non-ventilatory working muscle, likely due to hypoxemia.
Absolute Event Rate: 3.34% vs 0.49%
p-value: p=<0.01
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 et al. (Sat,) conducted a case-control in Chronic respiratory failure related to chronic obstructive pulmonary disease (n=16). Chronic respiratory failure related to COPD vs. Healthy age-matched subjects was evaluated on Pi/PCr ratio at 50% maximal voluntary contraction (p=<0.01). COPD patients with chronic respiratory failure exhibited a higher Pi/PCr ratio (3.34 vs 0.49; p<0.01) and lower intracellular pH (6.65 vs 7.06; p<0.01) during exercise compared to healthy controls.