The effect of red cell transfusion on nitric oxide diffusing capacity.

Background: The diffusion capacity of the lung for nitric oxide (DLNO) is supposed to reflect the properties of the alveolocapillary membrane better than the diffusion capacity of the lung for carbon monoxide (DLCO), due to a much stronger binding of NO to haemoglobin (Hb).

Objectives: The aim of this study was to investigate the effect of Hb concentration on the DLNO.

Methods: The DLNO and DLCO (single-breath method) were measured in 10 anaemic patients before and shortly after red cell transfusion.

Results: The mean increase in Hb concentration was 2.6 g/dl. Whereas DLCO increased as predicted by the reference equations, the DLNO did not change: mean DLCO rose from 13.6 to 16.5 ml/min/mm Hg (increase of 122%), mean DLCO corrected for Hb rose from 18.8 to 19.3 ml/min/mm Hg (103%) and mean DLNO rose from 75.6 to 77.8 ml/min/mm Hg (103%).

Conclusion: The DLNO is not influenced by Hb concentration.