Partitioning of the contributions of rib cage and abdomen to ventilation in ankylosing spondylitis

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Abstract
Grimby, G., Fugl-Meyer, A. R., and Blomstrand, A. (1974).Thorax,29, 179-184. Partitioning of the contributions of rib cage and abdomen to ventilation in ankylosing spondylitis. The relative contributions of the rib cage and abdomen to ventilation were studied in the sitting position in patients with ankylosing spondylitis, using measurements of changes in the anteroposterior diameters. The functional impairment of the spine and adjacent joints was also evaluated. In most patients vital capacity and total lung capacity were reduced, but functional residual capacity was normal. The relative contribution of the rib cage to ventilation was reduced at rest compared to normal subjects, and decreased further during hyperventilation induced by rebreathing. The end-expiratory level of the abdomen decreased more markedly during hyperventilation than in normal subjects and even the end-inspiratory level of the abdomen increased somewhat. The findings are consistent with a reduced mobility of the ribs and a greater than normal excursion of the diaphragm during breathing.