Membrane diffusing capacity and pulmonary capillary volume in rheumatoid disease.

Abstract

In some patients with rheumatoid disease gas transfer across the lungs is abnormal. We measured the membrane component of gas transfer (Dm) and pulmonary capillary volume (Vc) in 48 patients with rheumatoid arthritis and in 48 normal volunteers matched for age, sex, and smoking habits. Volunteers had normal chest radiographs and normal forced expiratory volume in one second and vital capacity. There were no significant differences between the rheumatoid and control groups for Dm. Mean Vc in rheumatoid male smokers (64-0 ml, SD 16-5) was significantly lower than in control male smokers (76-3 ml, SD 18-0 p<0 05). In rheumatoid female smokers mean Vc (43.4 ml, SD 13 3) was significantly lower than in rheumatoid female non-smokers (58.4 ml, SD 15-4 p<0 01). There was no significant difference between rheumatoid and control female non-smokers (mean Vc 58 4 ml and 60-7 ml respectively). Significant differences in Vc in terms of per cent predicted normal were found between patients receiving corticosteroids and those not receiving corticosteroids or penicillamine (p <0 02) and between patients with nodules and those without (p<0 05). Patients with persistently low transfer factor for five years had a significantly lower Vc (p<0 02). There was no consistent correlation between Dm and Vc and dynamic compliance or static recoil pressure. It appears that the abnormality of transfer factor in rheumatoid disease previously demonstrated is caused by reduction of Vc. It seems that involvement of pulmonary blood vessels occurs treatment with corticosteroids.

Measurement of carbon monoxide transfer and lung volume in ventilated subjects

“…The technique of assessing Dm and Ye by measuring TLco at different values of F10 2 was first described by ROUGHTON and FORSTER (3). It has been shown to be both accurate and reproducible, and has been used to assess change in Ye in a variety of pathological states including emphysema [13), rheumatoid arthritis [14), and pulmonary embolism [15). The mean value of 92 ml obtained for Ye measured during spontaneous respiration is similar to values reported in other studies of normal subjects.…”

“…In theory, measurements using this technique should only be undertaken using gas mixtures containing more than 28% oxygen [5), when it can reasonably be assumed that only Hb0 3 or Hb0 4 are present. However, a number of previous studies have utilized measurements with a Fro 2 of 21% and have still obtained reasonable values for Ye and Dm [13][14][15]. Moreover, we found no significant difference between V c and Dm calculated from measurements made in this study using 35 and 70% oxygen only, or from those values derived when all three oxygen levels were used.…”