Stiffness of the rib cage in a subset of rheumatoid patients

In a previous investigation of lung function in patients with rheumatoid arthritis (RA), we observed that some patients had significant dysfunction of their chest wall mechanics without pleural disease that could contribute to their respiratory symptoms. To investigate further the chest wall functions of patients with RA, we selected 10 female lifetime nonsmoking patients with RA and compared them to 10 paid normal volunteers in detailed functional evaluations of lung and chest wall. Patients with significant airflow limitation were excluded from this study. We found a significant 7% reduction in total lung capacity in the RA patients without significant change in lung compliance. However, we found a significant reduction in rib cage compliance in patients with RA (0.044 +/- 0.006 L/cmH2O vs. 0.064 +/- 0.012 in controls), which was associated with a significant 38% reduction in expansion of the rib cage volume during various breathing maneuvers. These changes occurred in the absence of lung or pleural disease. This study documents that patients with RA have limited expansion of rib cage relative to abdomen, thus rib cage restriction and stiffness, which may contribute to reduced lung volume. The shift of thoracoabdominal breathing configuration observed in patients with RA will likely reduce the effectiveness of breathing muscles and thus could contribute to the dyspnea sensation experienced by patients with RA.