title: Chronic effort dyspnea explained by lung function tests and by HRCT and CRX radiographic patterns in COPD: a post-hoc analysis in 51 patients.
abstract: This paper is a post-hoc analysis of a previous study performed to investigate the relationship between computerized tomography (CT) and lung function in 51 outpatients with mild-to-moderate COPD. We studied whether changes in lung function and radiographic patterns may help to explain dyspnea, the most disturbing symptom in patients with COPD. The Medical Research Council (MRC) dyspnea scale shows, by univariate analysis, a similar strength of association to CT expiratory lung density and to DL(CO), a functional index of lung parenchymal loss. The MRC dyspnea scale shows a somewhat less strength of association with a small vertical heart on plain chest films. In multivariate analysis, the model with the strongest association to the MRC dyspnea scale (r = 0.76, p < 0.0001) contains 4 explanatory variables (DL(CO), FRC, PaCO(2), and radiographic pattern of pulmonary hypertension). We suggest that diffusing capacity reflects the emphysematous component of hyperinflation, associated by definition with destruction of terminal airspace walls, as distinct from the air trapping component, which is ascribed to airway obstruction and associated with FRC. PaCO(2) mainly reflects the ventilatory components, i.e., ventilatory drive and ventilatory constraints, of pulmonary gas exchange in COPD, while radiographic pattern of pulmonary hypertension likely reflects hypoxic vascular changes, which depend mainly on ventilation/perfusion mismatch and give rise to pulmonary arterial hypertension that may contribute per se to dyspnea. In conclusion, our analysis points out that chronic effort dyspnea variance may account for up to 58% (r(2) = 0.58) by lung function tests and radiographic patterns. Thus, about 42% of the MRC dyspnea variance remains unexplained by this model. On the other hand, dyspnea ascertainment is dependent on subjective behavior and evaluation and in tests is influenced by individual performance and perception. For example in the 6-minute walk test, a similar or higher proportion (60%) of the overall variance is unexplained.
authors.affiliation: Section of Respiratory Diseases, Cardiothoracic Department, University of Pisa, Pisa, Italy. c.giuntini@med.unipi.it
authors.forename: Carlo
authors.initials: C
authors.lastname: Giuntini
authors.forename: Gianna
authors.initials: G
authors.lastname: Camiciottoli
authors.forename: Nazzarena Maria
authors.initials: NM
authors.lastname: Maluccio
authors.forename: Laura
authors.initials: L
authors.lastname: Mariani
authors.forename: Federico
authors.initials: F
authors.lastname: Lavorini
authors.forename: Massimo
authors.initials: M
authors.lastname: Pistolesi
mesh_terms: D000368:Aged; D002908:Chronic Disease; D004417:Dyspnea / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D013902:Radiography, Thoracic; D012129:Respiratory Function Tests; D012307:Risk Factors; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed