Is the carbon monoxide transfer factor diminished in the presence of diabetic retinopathy in patients with insulin-dependent diabetes mellitus?

Abstract

Impaired carbon monoxide gas transfer has been demonstrated in patients with insulin-dependent diabetes mellitus (IDDM), but no relationship has been documented between impairment of gas transfer and the presence of other clinical evidence of diabetic microangiopathy. This study set out to determine whether carbon monoxide gas transfer was related to the presence of microangiopathy by measuring the carbon monoxide transfer coefficient (KCO) in twenty patients with IDDM complicated by retinopathy, and in twenty patients without retinopathy. The patients were reasonably matched for age (mean 47 yrs in the retinopathy group, 41 yrs in the non-retinopathy group) but those with retinopathy had a longer mean duration of diabetes (23 yrs vs 13 yrs). Carbon monoxide transfer coefficient was normal in both groups, with no significant difference between them. Values for forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) were lower than predicted in the retinopathy group (92 (SEM 3.6%) and 91 (SEM 4.0%) respectively, p < 0.05) but were not significantly different from those in the non-retinopathy group. This study demonstrates normal lung function in IDDM, with no relationship between impairment of gas transfer and the presence of microangiopathy elsewhere.