Evaluation of respiratory impairment in patients with systemic lupus erythematosus with the six-minute walk test.

Objective: Evaluate SLE stable patients, without overt respiratory compromise, by means of 6MWT.
Casuistic and Methods: Forty-five stable SLE patients were enrolled. The ATS/ERS protocol for 6MWT, was used and two parameters with cut-off points were chosen.
Results: Forty-two patients were women. The mean age was 39 ± 11.4 years; mean duration of disease, 121 ± 93.1 months; mean value of MRC, 2 ± 0; mean FVC, 85.9 ± 34.2%; mean FEV1, 67.5 ± 21.6%; mean MIP, 82 ± 58.4%; mean MEP, 78 ± 37.3%; mean heart rate at rest, 75 ± 12.8 bpm; mean respiratory rate at rest, 19 ± 5.3 bpm; mean 6MWD, 478 ± 82 m; mean SpO2 at rest was 98 ± 0.8%; mean fall in SpO2, 4 ± 6 points. When the study population was divided according to the 400-m walk distance cut-off value, the heart rate immediately before the test was significant lower in those participants who walked less than 400 m (p = 0.0043), just like the value of Borg scale (p = 0.0036); according to the presence of saturation ≥ 4, heart rate at the end of the test was significantly higher in those participants who were showing desaturation (p = 0.0170); MEP (p = 0.0282) and 6MWD (p = 0.0291) were significantly lower, and MIP showed a tendency towards being smaller (p = 0.0504). FVC < normal inferior limit was significantly associated with the group with desaturation (p = 0.0274).
Conclusion: Compared to 6MWD, desaturation was better suited to find the patients with the most compromised indexes in respiratory function tests.