title: Relationship between frequency dependence of lung compliance and distribution of ventilation.
abstract: The previously demonstrated empirical association between frequency dependence of lung compliance and distribution of ventilation, the latter determined by the N(2) washout technique, was confirmed by establishing a mathematical link between the two tests. By assuming a two-compartment system with known compliances and making corrections for Pendelluft and common dead space mixing effects, the ratio of dynamic to static compliance (C(dyn)/C(st)) for any respiratory frequency can be calculated from the compartmental analysis of the N(2) washout at a single respiratory frequency. By using these equations, a good correlation was found between calculated and measured C(dyn)/C(st) in dogs with artificially induced bronchial obstruction and in young smokers or young nonsmokers after carbachol inhalation. A two-compartment N(2) washout was demonstrated in 10 young healthy smokers at one or two respiratory frequencies whereas all 10 normal controls showed a single exponential curve. These findings indicate that the non-invasive N(2) washout test is capable of predicting C(dyn)/C(st) and at the same time gives a direct measure of gas distribution. Further, it appears to be a highly sensitive method for the detection of "small airway disease."
mesh_terms: D000328:Adult; D000402:Airway Obstruction / Q000139:chemically induced / Q000503:physiopathology; D000818:Animals; D000886:Anthropometry; D001980:Bronchi / Q000503:physiopathology; D002217:Carbachol / Q000009:adverse effects; D004285:Dogs; D005260:Female; D006801:Humans; D008170:Lung Compliance; D008297:Male; D008433:Mathematics; D008954:Models, Biological; D009584:Nitrogen; D012119:Respiration; D012126:Respiratory Dead Space; D012129:Respiratory Function Tests; D014797:Vital Capacity
chemical_list: D002217:Carbachol; D009584:Nitrogen