Use of lung mechanics to identify early pulmonary involvement in patients with ankylosing sp01sdylitis

We studied if a detailed analysis of lung mechanics could help in ealrly recognition of pulmonary abnormalities in patients with ankylosing spondylitis. Methods: Static pulmonary mechanics were studied in 17 patients ( 16 men and one woman ) of ankylosing spondylitis with no obvious clinical or radiological evidence of pulmonary involvement. Lung pressure-volume relationship was generated using a whole body plethysmograph. and a monoexponential equation fitted to this data. Results: Total lung capacity (TLC) was reduced in one (5.9%) and static lung compliance (Cst) in 9 (52.9%) patients. Four (23.5%) patients had normal TLC. yet Csl and shape constant (K) were reduced. Five (29.4%) patients had reduced TLC and Csl ; four of them had low K. One (5.9%) patient had normal TLC but elevated C_st and K. Conclusion: This suggests that pulmonary involvement in these patients is probably diffuse and begins much earlier than generally presumed. Evaluation of static lung mechanics can identify pulmonary involvement early in the course of disease in several of these patients.