title: Deciphering the nitric oxide to carbon monoxide lung transfer ratio: physiological implications.
abstract: Using simultaneous nitric oxide and carbon monoxide lung transfer measurements (T(LNO) and T(LCO)), the membrane transfer capacity (D(m)) and capillary lung volume (V(c)) as well as the dimensionless ratio T(LNO)/T(LCO) can be calculated. The significance of this ratio is yet unclear. Theoretically, the T(LNO)/T(LCO) ratio should be inversely related to the product of both lung alveolar capillary membrane (mu) and blood sheet thicknesses (K). NO and CO transfers were measured in healthy subjects in various conditions likely to be associated with changes in K and/or mu. Experimentally, deflation of the lung from 7.4 to 4.8 l decreased the T(LNO)/T(LCO) ratio from 4.9 to 4.2 (n=25) which was consistent mainly with a thickening of the blood sheet. Compared with continuous negative pressure breathing, continuous positive pressure breathing increased this ratio suggesting a thinning of the capillary sheet. It was also observed with 12 healthy subjects that slight haemodilution that may thicken the blood sheet decreased the T(LNO)/T(LCO) ratio from 4.85 to 4.52. In conclusion, the T(LNO)/T(LCO) ratio is related to the thickness of the alveolar blood barrier. This ratio provides novel information for the analysis of the diffusion properties.
authors.affiliation: Laboratoire de Physiologie, Université Victor Segalen, 146 Rue Léo Saignat, 33076 Bordeaux Cedex, France.
authors.forename: Stéphane N
authors.initials: SN
authors.lastname: Glénet
authors.forename: Claire
authors.initials: C
authors.lastname: De Bisschop
authors.forename: Frederic
authors.initials: F
authors.lastname: Vargas
authors.forename: Hervé J P
authors.initials: HJ
authors.lastname: Guénard
mesh_terms: D000328:Adult; D000375:Aging / Q000502:physiology; D002196:Capillaries; D002248:Carbon Monoxide / Q000097:blood; D005260:Female; D006438:Hemodilution; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009569:Nitric Oxide / Q000097:blood; D011175:Positive-Pressure Respiration; D011650:Pulmonary Alveoli; D011652:Pulmonary Circulation; D011653:Pulmonary Diffusing Capacity; D015203:Reproducibility of Results
chemical_list: D009569:Nitric Oxide; D002248:Carbon Monoxide