Mechanisms for reduced pulmonary diffusing capacity in haematopoietic stem-cell transplantation recipients.

recipients. We derived alveolar–capillary membrane conductance (DM,CO) and pulmonary capillary vol-ume (VC) from DLCOand diffusing capacity for NO (DLNO). Forty patients were studied before and 6 weeksafter HSCT. Before HSCT, DLNOand DLCOwere significantly lower than in 30 healthy controls. DM,COwas∼40% lower in patients than in controls (p < 0.001), whereas VCdid not differ significantly. After HSCT,DLNOand DM,COfurther decreased, the latter by ∼22% from before HSCT (p < 0.01) while VCdid not changesignificantly. Lung density, serum CRP and reactive oxygen metabolites were significantly increased, withthe latter being correlated (R2= 0.71, p < 0.001) with the decrement in DLNO. We conclude that DLNOand,to a lesser extent, DLCOare compromised before HSCT mainly due to a DM,COreduction. A further reduc-tion of DM,COwithout VCloss occurs after HSCT, possibly related to development of oedema, or interstitialfibrosis, or both.