Respiratory Muscle Function and Spirometry in Patients with Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) can affect all organ systems including the respiratory tract and skeletal muscles. Some of the respiratory findings can be attributed to respiratory muscle involvement. The purpose of this study was to clarify the characteristics of pulmonary function tests (PFT), especially maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP) in females with systemic lupus erythematosus (SLE). During a 12-mounth period, forced vital capacity (FVC), FEV1, FEF25-75, MIP, and MEP were measured prospectively in 76 consecutive female patients, suffering active SLE. The measured values were compared to an age-matched group of healthy women. FVC was lower in the patients than in controls (2.81versus 3.64) P=0.000. Maximal inspiratory pressure (PImax) was lower in the female patients than in 78 controls (3.42 versus 7.36)P=0.000. Maximal expiratory pressure (PEmax) was lower in the female patients than in controls (4.14versus 9.68 kPa) P=0.000, There were no correlations between PImax or PEmax and parameters of disease activity. Mouth occlusion pressure within the first 0.1 s of inspiration was higher in SLE patients than in controls (2.43 versus 1.38); however, the difference was not statistically significant (P=0.16). This study provides evidence of inspiratory and expiratory muscle weakness in SLE and may cause FVC reduction as well. The pathophysiologic mechanisms and the prognostic significance should be further investigated.(Tanaffos 2006; 5(4): 53-58)