A pilot study of office-based spirometry in patients with systemic lupus erythematosus.

Background: Although pulmonary involvement is common in systemic lupus erythematosus (SLE), its effects on healthy lifestyle physical activity and its association with fatigue have not been well characterized. The goals of this study were to describe pulmonary function measured by office-based spirometry in patients with SLE and to compare spirometry with physical activity and systemic fatigue.

Methods: During an office visit, 49 patients with SLE completed spirometry assessing: a) forced expiratory volume in 1 s (FEV(1), a measure of airway patency and responsiveness); b) forced vital capacity (FVC, a measure of lung volume); and c) maximum voluntary ventilation (MVV, a measure of volume of air moved during rapid breathing) which has been hypothesized to be decreased in SLE due to muscle fatigue. Patients also performed a 2-min corridor walking test and completed self-reported questionnaires measuring weekly physical activity and systemic fatigue.

Results: Mean age was 45 years, 45 (92%) were women, mean SLEDAI and SLICC scores were 2.8 and 1.0, respectively. Some 24 patients had a smoking history, and 15 had a history of SLE-related pleuritis, which was not active at enrollment. FEV(1) and FVC were 96% of predicted, but MVV was only 55% of predicted. The distance walked during the corridor test was similar to that of patients with other chronic diseases; however, self-reported physical activity was less than recommended by national guidelines. There were no associations between spirometry values and history of pleuritis, other pulmonary diagnoses, or smoking (p > .10 for all comparisons), however, better FEV(1) (p = .04) and better FVC (p = .04) were associated with more self-reported activity and better FEV(1) (p = .03) was associated with longer distance walked during the corridor test. Most patients reported marked systemic fatigue; however, there were no associations between spirometry values and fatigue scores (p > .10 for all comparisons).

Conclusions: MVV was markedly diminished, which supports the hypothesis that SLE may be associated with respiratory muscle fatigue during rapid breathing. MVV was not associated with mild-to-moderate patient-directed physical activity; however, lower FEV(1) and FVC were associated with less self-reported and performance-based physical activity.