Early respiratory physiological impairment in progressive systemic sclerosis and ankylosing spondylitis

Respiratory physiological parameters [pulmonary function tests, diffusing capacity, mouth occlusion pressure, maximal inspiratory and expiratory pressures as well as abdomino-thoracic movements] were studied in 10 patients of progressive systemic sclerosis [PSS] and 10 patients of ankylosing spondylitis [AS]. All patients were studied before the development of any respiratory symptomatology and even before the appearance of any roentgenographic abnormalities. Patients of both PSS and AS showed a restrictive pulmonary dysfunction with evidence of small airway obstruction and alveolar capillary block. They also showed an increase in respiratory centre activity, and impaired respiratory muscle performance, but their abdomino-thoracic synchronized movements were normal. In addition to the previous findings, patients of AS showed an increase in RV and RV/TLC ratio reflecting an obstructive pulmonary dysfunction and air trapping in addition to the predominant restrictive dysfunction