Pulmonary membrane diffusing capacity and capillary blood volume in tropical eosinophilia.

Pulmonary membrane diffusing capacity (Dm) and pulmonary capillary blood volume (Vc) measurements were carried out in 21 patients with untreated tropical eosinophilia and 21 healthy controls matched for age, sex, height, and smoking habit. The mean single breath transfer factor (Dco) and the mean membrane diffusing capacity were significantly lower (p less than 0.001) in patients with tropical eosinophilia compared with control subjects. However, the mean capillary blood volume was not significantly different (p greater than 0.2). The positive correlations between Dm and transfer factor (r = 0.825), between Dm and effective alveolar volume (VA) (r = 0.721), and between Dco and VA (r = 0.774) were also highly significant (p less than 0.001) in study patients prior to treatment. These data suggest that reduction in single breath transfer factor in untreated tropical eosinophilia may be due to a reduction in membrane diffusing capacity, which in turn may be due to a reduction in area of membrane available for diffusion, as evidenced by the significantly reduced VA (p less than 0.001) in these patients. Since pulmonary capillary blood volume was normal, the pulmonary perfusion was within normal limits. Following three weeks of treatment with diethylcarbamazine citrate, although there was a significant rise in single breath transfer factor (p less than 0.001) and membrane diffusing capacity (p less than 0.05), both Dco (p less than 0.01) and Dm (p less than 0.01) continued to be significantly lower than those of control subjects. However, pulmonary capillary blood volume did not show any change (p greater than 0.2).