%0 Journal Article
%T Concave Pattern of a Maximal Expiratory Flow-Volume Curve: A Sign of Airflow Limitation in Adult Bronchial Asthma
%A Akihiko Ohwada
%A Kazuhisa Takahashi
%J Pulmonary Medicine
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/797495
%X Background. In patients with bronchial asthma, spirometry could identify the airflow limitation of small airways by evaluating the concave shape of the maximal expiratory flow-volume (MEFV) curve. As the concave shape of the MEFV curve is not well documented, we reevaluated the importance of this curve in adult asthmatic patients. Methods. We evaluated spirometric parameters, the MEFV curve, and its concave shape (scoop between the peak and endpoint of expiration) in 27 nonsmoking asthmatic patients with physician-confirmed wheeze and positive bronchial reversibility after a short-acting ¦Â2-agonist inhalation. We also calculated angle ¦Â and shape factors ( and ) to quantitate the curvilinearity of the MEFV curve. Results. The MEFV curve was concave in all patients. Along with improvements in standard spirometric parameters, curvilinear parameters, angle ¦Â, , and were significantly improved after bronchodilator inhalation. There were significant correlations between improvements in angle ¦Â, and , and , and between improvements in , and , and . Conclusions. The bronchodilator greatly affected the concave shape of the MEFV curve, correlating with spirometric parameters of small airway obstructions ( , , and ). Thus, the concave shape of the MEFV curve is an important indicator of airflow limitation in adult asthmatic patients. 1. Introduction Evaluation of airflow limitation is crucial for diagnosis of bronchial asthma and chronic obstructive pulmonary diseases. Spirometry is a simple but important procedure to detect airflow limitation. Reductions of forced expiratory volume in 1£¿s (FEV1), FEV1/forced vital capacity (FVC) ratio, and peak expiratory flow (PEF) are proven signs [1]. In the 1970s and 80s, analysis of the configuration of maximal expiratory flow-volume (MEFV) curve concluded that the concave shape of the MEFV curve reflects the presence of small airway obstructions. Kraan et al. analyzed the changes in the MEFV curve in patients with bronchial asthma after treatment with inhaled steroids using indices of curvilinearity of the MEFV curve, shape factors (SFs), and slope ratio (SR) [2]. They revealed that the shape of the curve became less bowed toward the volume axis after inhaled corticosteroids and concluded that such a change in the MEFV curve reflects a decrease in the inhomogeneous distribution of airflow narrowing. Kapp et al. defined a new parameter, angle ¦Â, to characterize the shape of the MEFV curve and revealed that patients with asthma, chronic bronchitis, dyspnea, and wheeze had significantly lower ¦Â angles than healthy individuals
%U http://www.hindawi.com/journals/pm/2012/797495/