Reduced muscle uptake of oxygen during exercise in patients with systemic lupus erythematosus.

OBJECTIVE

To assess the factors limiting aerobic exercise capacity in patients with systemic lupus erythematosus (SLE).

METHODS

The anaerobic threshold (AT) and O2 pulse, i.e., VO2/heart rate (HR), were measured in 21 patients with SLE without cardiopulmonary complications by the analysis of expired gas during incremental work load in exercise testing. The relationships between work rate (WR) and VO2, HR and VO2/weight (Wt), and lupus activity index (LAI) and AT were analyzed.

RESULTS

The AT of the patients with SLE was significantly lower than for a control group. Little increase in O2 pulse and very low delta VO2/delta WR and delta VO2/Wt@delta HR were found during work load in some patients with SLE, especially those with a low AT and high LAI. Patients with SLE with a high LAI tended to show a low AT.

CONCLUSION

The low aerobic exercise capacity of patients with SLE appeared to be mainly due to a small increase in O2 pulse. This may have resulted from impaired oxygen diffusion in the inflamed peripheral muscles in patients with active SLE. Low AT may explain in part why patients with SLE become easily fatigued.