title: Frequency dependence of compliance in the evaluation of patients with unexplained respiratory symptoms.
abstract: Frequency dependence of compliance (FDC) reflects non-homogeneous ventilatory distribution and, in the presence of a normal measured airway resistance, suggests peripheral airways dysfunction. This study evaluated peripheral airway function and bronchial reactivity in irritant exposed or non-exposed individuals with normal routine pulmonary function tests (PFTs) who had persistent unexplained lower respiratory symptoms. Twenty-two patients were identified with persistent respiratory symptoms and with normal chest X-ray and PFTs. Twenty were non-smokers; two had stopped smoking more than 10 years before evaluation. Twelve patients had been exposed to irritants in their workplaces or at home. Non-specific bronchial hyper-reactivity (nsBHR) and FDC, pre- and post-bronchodilator, were measured in all patients. Studies were repeated in 6/12 irritant-exposed subjects after exposure removal and inhaled corticosteroid treatment. Whereas 12/22 patients had nsBHR, all 22 subjects demonstrated FDC [dynamic lung compliance/static lung compliance Cdyn,1 / Cst,1 at respiratory frequency 60 min(-1) (f60), mean 46%, range 27-67%]. After bronchodilator administration, a 15% improvement Cdyn,1 was observed most consistently at f60 (mean% improvement 26%, 95% CI 14-38%) and in subjects without nsBHR. However, Cdyn,1 at f60 did not return to normal after inhaled bronchodilator. Irritant-exposed and unexposed individuals appeared similar in results of testing for FDC and nsBHR. FDC and its response to bronchodilators provide objective physiological measures of an airway abnormality which may provide a basis for clinical symptoms in patients with normal routine pulmonary function studies. The presence of persistently abnormal FDC after bronchodilator (BD) and on follow up studies may reflect chronic inflammatory and/or structural changes in the airways in addition to bronchoconstriction.
authors.affiliation: New York University School of Medicine, Department of Medicine, Bellevue Hospital Center, NY, USA. red3@nyu.edu
authors.forename: R E
authors.initials: RE
authors.lastname: de la Hoz
authors.forename: K I
authors.initials: KI
authors.lastname: Berger
authors.forename: T T
authors.initials: TT
authors.lastname: Klugh
authors.forename: G
authors.initials: G
authors.lastname: Friedman-Jiménez
authors.forename: R M
authors.initials: RM
authors.lastname: Goldring
mesh_terms: D000328:Adult; D016535:Bronchial Hyperreactivity / Q000503:physiopathology; D001993:Bronchodilator Agents / Q000627:therapeutic use; D005260:Female; D005500:Follow-Up Studies; D005938:Glucocorticoids / Q000627:therapeutic use; D006801:Humans; D007509:Irritants / Q000009:adverse effects; D008170:Lung Compliance / Q000187:drug effects; D008173:Lung Diseases, Obstructive / Q000188:drug therapy / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012129:Respiratory Function Tests
chemical_list: D001993:Bronchodilator Agents; D005938:Glucocorticoids; D007509:Irritants