title: Mechanical correlates of dyspnea in bronchial asthma.
abstract: We hypothesized that dyspnea and its descriptors, that is, chest tightness, inspiratory effort, unrewarded inspiration, and expiratory difficulty in asthma reflect different mechanisms of airflow obstruction and their perception varies with the severity of bronchoconstriction. Eighty-three asthmatics were studied before and after inhalation of methacholine doses decreasing the 1-sec forced expiratory volume by ~15% (mild bronchoconstriction) and ~25% (moderate bronchoconstriction). Symptoms were examined as a function of changes in lung mechanics. Dyspnea increased with the severity of obstruction, mostly because of inspiratory effort and chest tightness. At mild bronchoconstriction, multivariate analysis showed that dyspnea was related to the increase in inspiratory resistance at 5 Hz (R 5) (r (2) = 0.10, P = 0.004), chest tightness to the decrease in maximal flow at 40% of control forced vital capacity, and the increase in R 5 at full lung inflation (r (2) = 0.15, P = 0.006), inspiratory effort to the temporal variability in R 5-19 (r (2) = 0.13, P = 0.003), and unrewarded inspiration to the recovery of R 5 after deep breath (r (2) = 0.07, P = 0.01). At moderate bronchoconstriction, multivariate analysis showed that dyspnea and inspiratory effort were related to the increase in temporal variability in inspiratory reactance at 5 Hz (X 5) (r (2) = 0.12, P = 0.04 and r (2) = 0.18, P < 0.001, respectively), and unrewarded inspiration to the decrease in X 5 at maximum lung inflation (r (2) = 0.07, P = 0.04). We conclude that symptom perception is partly explained by indexes of airway narrowing and loss of bronchodilatation with deep breath at low levels of bronchoconstriction, but by markers of ventilation heterogeneity and lung volume recruitment when bronchoconstriction becomes more severe.
authors.affiliation: Allergologia e Fisiopatologia Respiratoria, ASO S. Croce e Carle, Cuneo, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Antonelli
authors.affiliation: Fisiopatologia Respiratoria, Dipartimento di Medicina Interna, Università di Genova, Genova, Italy.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Crimi
authors.affiliation: TBM Lab, Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Gobbi
authors.affiliation: Pneumologia-Fisiopatologia Respiratoria, AOU S. Luigi Gonzaga, Orbassano (Torino), Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Torchio
authors.affiliation: Pneumologia-Fisiopatologia Respiratoria, AOU S. Luigi Gonzaga, Orbassano (Torino), Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Gulotta
authors.affiliation: TBM Lab, Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Dellaca
authors.affiliation: Dipartimento di Medicina Interna, Sezione di Immunologia Clinica, Allergologia e Malattie Respiratorie, Università di Firenze, Firenze, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Scano
authors.affiliation: Fisiopatologia Respiratoria, Dipartimento di Medicina Interna, Università di Genova, Genova, Italy.
authors.forename: Vito
authors.initials: V
authors.lastname: Brusasco
authors.affiliation: Allergologia e Fisiopatologia Respiratoria, ASO S. Croce e Carle, Cuneo, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Pellegrino
keywords: Airway mechanics; dyspnea descriptors; forced oscillation technique; lung hyperinflation; methacholine
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