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 β2-agonist inhalation. We also calculated angle β 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 β, , and were significantly improved after bronchodilator inhalation. There were significant correlations between improvements in angle β, 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 β, to characterize the shape of the MEFV curve and revealed that patients with asthma, chronic bronchitis, dyspnea, and wheeze had significantly lower β angles than healthy individuals
References
[1]
Global Initiative for Asthma (GINA), “Global strategy for asthma management and prevention,” NHLBI/WHO Workshop Report, National Institutes of Health, National Heart, Lung and Blood Institute, Bethesda, Md, USA, 2009.
[2]
J. Kraan, T. W. van der Mark, and G. H. Koeter, “Changes in maximum expiratory flow-volume curve configuration after treatment with inhaled corticosteroids,” Thorax, vol. 44, no. 12, pp. 1015–1021, 1989.
[3]
M. C. Kapp, E. N. Schachter, G. J. Beck, L. R. Maunder, and T. J. Witek, “The shape of the maximum expiratory flow volume curve,” Chest, vol. 94, no. 4, pp. 799–806, 1988.
[4]
R. Pellegrino, G. Viegi, V. Brusasco et al., “Interpretative strategies for lung function tests,” European Respiratory Journal, vol. 26, no. 5, pp. 948–968, 2005.
[5]
M. R. Miller, J. Hankinson, V. Brusasco et al., “Standardisation of spirometry,” European Respiratory Journal, vol. 26, no. 2, pp. 319–338, 2005.
[6]
Japanese Respiratory Society, “Standard reference values of spirometric parameters and arterial blood gas analysis,” (Author translated) in Japanese, The Japanese Respiratory Society Journalhttp://www.jrs.or.jp/quicklink/glsm/guideline/nopass_pdf/spirogram.pdf, 2004.
[7]
J. L. Hankinson, J. R. Odencrantz, and K. B. Fedan, “Spirometric reference values from a sample of the general U.S. population,” American Journal of Respiratory and Critical Care Medicine, vol. 159, no. 1, pp. 179–187, 1999.
[8]
A. Bouhuys, “Pulmonary function measurements in epidemiological studies,” Bull Eur Physiopathol Respir, vol. 6, no. 3, pp. 561–578, 1970.
[9]
C. K. W. Lai, R. Beasley, J. Crane et al., “Global variation in the prevalence and severity of asthma symptoms: phase three of the International Study of Asthma and Allergies in Childhood (ISAAC),” Thorax, vol. 64, no. 6, pp. 476–483, 2009.
[10]
Y. Fukutomi, M. Taniguchi, J. Watanabe, et al., “Time trend in the prevalence of adult asthma in Japan: findings from population-based surveys in Fujieda City in 1985, 1999, and 2006,” Allergology International, vol. 60, no. 4, pp. 443–448, 2011.
[11]
S. W. Yancey and H. G. Ortega, “Retrospective characterization of airway reversibility in patients with asthma responsive to bronchodilators,” Current Medical Research and Opinion, vol. 23, no. 12, pp. 3205–3207, 2007.
[12]
A. Ohwada, K. Inami, E. Onuma, M. Matsumoto-Yamazaki, R. Atsuta, and K. Takahashi, “Bronchial reversibility with a short-acting β2-agonist predicts the FEV1 response to administration of a long-acting β2-agonist with inhaled corticosteroids in patients with bronchial asthma,” Experimental and Therapeutic Medicine, vol. 2, no. 4, pp. 619–623, 2011.
[13]
W. C. Moore, E. R. Bleecker, D. Curran-Everett et al., “Characterization of the severe asthma phenotype by the National Heart, Lung, and Blood Institute's Severe Asthma Research Program,” Journal of Allergy and Clinical Immunology, vol. 119, no. 2, pp. 405–413, 2007.
[14]
R. L. Sorkness, E. R. Bleecker, W. W. Busse et al., “Lung function in adults with stable but severe asthma: air trapping and incomplete reversal of obstruction with bronchodilation,” Journal of Applied Physiology, vol. 104, no. 2, pp. 394–403, 2008.
[15]
J. Mead, “Analysis of the configuration of maximum expiratory flow-volume curves,” Journal of Applied Physiology Respiratory Environmental and Exercise Physiology, vol. 44, no. 2, pp. 156–165, 1978.
[16]
O. Omland, T. Sigsgaard, O. F. Pedersen, and M. R. Miller, “The shape of the maximum expiratory flow-volume curve reflects exposure in farming,” Annals of Agricultural and Environmental Medicine, vol. 7, no. 2, pp. 71–78, 2000.
[17]
R. Drewek, E. Garber, S. Stanclik, P. Simpson, M. Nugent, and W. Gershan, “The FEF25-75 and its decline as a predictor of methacholine responsiveness in children,” Journal of Asthma, vol. 46, no. 4, pp. 375–381, 2009.
[18]
O. Linna, “A doctor's ability to assess the severity of childhood asthma by simple clinical features,” Acta Paediatrica, vol. 94, no. 5, pp. 559–563, 2005.
[19]
Y. Zhang, R. McConnell, F. Gilliland, and K. Berhane, “Ethnic differences in the effect of asthma on pulmonary function in children,” American Journal of Respiratory and Critical Care Medicine, vol. 183, no. 5, pp. 596–603, 2011.
[20]
V. Nève, R. Matran, G. Baquet, et al., “Quantification of shape of flow-volume loop of healthy preschool children and preschool children with wheezing disorders,” Pediatric Pulmonology, vol. 47, no. 9, pp. 884–894, 2012.
[21]
M. Contoli, J. Bousquet, L. M. Fabbri et al., “The small airways and distal lung compartment in asthma and COPD: a time for reappraisal,” Allergy, vol. 65, no. 2, pp. 141–151, 2010.
[22]
M. Contoli, M. Kraft, Q. Hamid, et al., “Do small airway abnormalities characterize asthma phenotypes? In search of proof,” Clinical & Experimental Allergy, vol. 42, no. 8, pp. 1150–1160, 2012.
