The effect of postural change on the coefficient of diffusion in sarcoidosis patients

Granulomatous angiitis is common in sarcoidosis. To test the hypothesis that patients with sarcoidosis have an impaired ability to recruit or to distend the pulmonary vascular bed, the postural change in the coefficient of diffusion (ratio of DCO to alveolar volume) for carbon monoxide was measured in 20 patients with sarcoidosis and in 10 normal subjects. The normal control group increased the coefficient of diffusion (KCO) by 12.8% (p, 0.05), when values at sitting position were compared to values at supine position. The sarcoidosis group did not significantly increase the coefficient with change in position. The absence of an increase in the coefficient of diffusion (KCO) in sarcoidosis with change in position may indicate vascular involvement.