Lung Diffusing Capacity for Nitric Oxide and Carbon Monoxide After Hematopoietic Stem-cell Transplantation (DLNO/DLCO)

In allogeneic hematopoietic stem-cell transplantation (allo-HSCT) recipients, early reductions of absolute lung volume and diffusing capacity for carbon monoxide (DLCO) are frequently detected even in the absence of overt idiopathic pneumonia syndrome (IPS)[PMID: 22221781]. Two months after allo-HSCT, we have recently shown an increase in lung tissue density determined by quantitative CT scan [PMID: 22898044]. It can be hypothesized that these parenchymal changes might be due to an occult intersitial lung disease associated with infections, acute Graft-versus-Host Disease (aGvHD), myeloablative conditioning regimens or any combination of these [PMID: 21531955]. To test this hypothesis, we will simultaneously measure the lung diffusing capacity for nitric oxide (DLNO) and DLCO. Assuming, for clinical purposes, that the reaction rate of NO with blood hemoglobin is infinite so that DLNO = DMNO = DMCO*alpha (alpha = NO/CO diffusivity ratio), as to partition the effect of HSCT on membrane diffusing capacity (DM) and pulmonary capillary volume (Vc) we will use the DLNO/DLCO ratio [PMID:16478855]. As we hypothesize that GHVD should be intuitively absent amongst autologous HSCT (auto-HSCT) recipients, we will compare the changes in DLNO/DLCO ratio showed by the latter group with those of subjects undergoing allo-HSCT.