title: The DLNO/DLCOratio: Physiological significance and clinical implications.
abstract: DLNO/DLCOdirectly measures the ratio of the diffusing capacities of the lung for nitric oxide (NO) and carbon monoxide (CO). In terms of the Roughton and Forster (1957) equation, 1/DL=1/Dm+1/θVc, where Dm is the membrane (Dm) and θVc is the red cell component of the overall diffusing conductance (DL); DLNOmostly reflects the Dm component and DLCOthe θVc red cell component. The DLNO/DLCOratio is positively related to the DmCO/Vc ratio and the CO red cell resistance (1/θCOVc) as a percentage of the total resistance (1/DLCO), independent of the absolute values of DLNOor DLCO. In clinical studies, a raised DLNO/DLCOratio (≥110% predicted versus a control group), plus a low DLNOand DLCO(<67% pred), predicts pulmonary vascular disease, while a low DLNO/DLCOratio, with similarly reduced DLNOand DLCO, is associated with interstitial lung disease with fibrosis. More clinical studies are needed, and reference values need to be better defined.
authors.affiliation: National Heart and Lung Institute, Imperial College, London, United Kingdom. Electronic address: mike.hughes@imperial.ac.uk.
authors.forename: J M B
authors.initials: JMB
authors.lastname: Hughes
authors.affiliation: Department of Physiology, Cochin Hospital, Assistance Publique, Hôpitaux de Paris, Medical School, Paris Descartes University, Paris, France. Electronic address: anh-tuan.dinh-xuan@aphp.fr.
authors.forename: A T
authors.initials: AT
authors.lastname: Dinh-Xuan
mesh_terms: D000818:Animals; D002248:Carbon Monoxide; D006801:Humans; D008168:Lung / Q000502:physiology; D008955:Models, Cardiovascular; D009569:Nitric Oxide; D011653:Pulmonary Diffusing Capacity
chemical_list: D009569:Nitric Oxide; D002248:Carbon Monoxide
keywords: Carbon monoxide; Diffusing capacity; Gas exchange; Lung function; Nitric oxide; Transfer factor