Dynamic hyperinflation and flow limitation during methacholine-induced bronchoconstriction in asthma

Although persistent activation of the inspiratory muscles and narrowing of the glottic aperture during expiration have been indicated as relevant mechanisms leading to dynamic hyperinflation in acute asthma, expiratory flow limitation (EFL) has recently been proposed as a possible triggering factor for increasing endexpiratory lung volume (EELV). To establish whether the attainment of maximal flow rate during tidal expiration could elicit dynamic elevation of EELV, breathing pattern, change in EELV by measuring inspiratory capacity (IC) and occurrence of EFL by the negative expiratory pressure (NEP) method were monitored in 10 stable asthmatic subjects during methacholine-induced, progressive bronchoconstriction in seated position. Change in dyspnoea was scored using the Borg scale. At maximum response forced expiratory volume in one second (FEV1) fell on average by 45+/-2% (p<0.001 versus control), while IC decreased 29+/-2%, (by 0.89+/-0.07 L, (p<0.01 versus control)). Only 2 subjects exhibited EFL at the end of methacholine challenge. In 7 subjects EELV started to increase before the occurrence of EFL. Dyspnoea, which increased from 0.2+/-0.1 to 5.5+/-1.0 (Borg scale) at maximum response (p<0.001), was significantly related to the level of bronchoconstriction as assessed by change in (delta)FEV1 (r=0.72; p<0.001) and to dynamic hyperinflation as measured by deltaIC (r=0.50; p<0.001). However, for both deltaFEV1 and deltaIC the slope of the relationship with increasing dyspnoea was highly variable among the subjects. It is concluded that in acute methacholine-induced bronchoconstriction, dynamic hyperinflation may occur in the absence of expiratory flow limitation and that expiratory flow limitation does not represent the triggering factor to generate dynamic hyperinflation. In these circumstances, dyspnoea appears to be related to the increase in end-expiratory lung volume and not to the onset of expiratory flow limitation.

This article has been cited by other articles:

				R. L. Dellaca, N. Duffy, P. P. Pompilio, A. Aliverti, N. G. Koulouris, A. Pedotti, and P. M. A. Calverley Expiratory flow limitation detected by forced oscillation and negative expiratory pressure Eur. Respir. J., February 1, 2007; 29(2): 363 - 374. [Abstract] [Full Text] [PDF]

				M. D. Lougheed, T. Fisher, and D. E. O'Donnell Dynamic hyperinflation during bronchoconstriction in asthma: implications for symptom perception. Chest, October 1, 2006; 130(4): 1072 - 1081. [Abstract] [Full Text] [PDF]

				R. S. Harris, T. Winkler, N. Tgavalekos, G. Musch, M. F. V. Melo, T. Schroeder, Y. Chang, and J. G. Venegas Regional Pulmonary Perfusion, Inflation, and Ventilation Defects in Bronchoconstricted Patients with Asthma Am. J. Respir. Crit. Care Med., August 1, 2006; 174(3): 245 - 253. [Abstract] [Full Text] [PDF]

				C. M. Parker, N. Voduc, S. D. Aaron, K. A. Webb, and D. E. O'Donnell Physiological changes during symptom recovery from moderate exacerbations of COPD Eur. Respir. J., September 1, 2005; 26(3): 420 - 428. [Abstract] [Full Text] [PDF]

				P. M. A. Calverley and N. G. Koulouris Flow limitation and dynamic hyperinflation: key concepts in modern respiratory physiology Eur. Respir. J., January 1, 2005; 25(1): 186 - 199. [Abstract] [Full Text] [PDF]

				E.N. Kosmas, J. Milic-Emili, A. Polychronaki, I. Dimitroulis, S. Retsou, M. Gaga, A. Koutsoukou, Ch. Roussos, and N.G. Koulouris Exercise-induced flow limitation, dynamic hyperinflation and exercise capacity in patients with bronchial asthma Eur. Respir. J., September 1, 2004; 24(3): 378 - 384. [Abstract] [Full Text] [PDF]

				F. C. Sciurba Physiologic Similarities and Differences Between COPD and Asthma Chest, August 1, 2004; 126(2_suppl_1): 117S - 124S. [Abstract] [Full Text] [PDF]

				P.-H. Wang, P.-H. Kuo, C.-L. Hsu, H.-D. Wu, Y.-S. Chang, S.-H. Kuo, and P.-C. Yang Diagnostic Value of Negative Expiratory Pressure for Airway Hyperreactivity Chest, November 1, 2003; 124(5): 1762 - 1767. [Abstract] [Full Text] [PDF]

				N.G. Koulouris, S. Retsou, E. Kosmas, K. Dimakou, K. Malagari, G. Mantzikopoulos, A. Koutsoukou, J. Milic-Emili, and J. Jordanoglou Tidal expiratory flow limitation, dyspnoea and exercise capacity in patients with bilateral bronchiectasis Eur. Respir. J., May 1, 2003; 21(5): 743 - 748. [Abstract] [Full Text] [PDF]

				D. Goetghebeur, D. Sarni, Y. Grossi, C. Leroyer, H. Ghezzo, J. Milic-Emili, and M. Bellet Tidal expiratory flow limitation and chronic dyspnoea in patients with cystic fibrosis Eur. Respir. J., March 1, 2002; 19(3): 492 - 498. [Abstract] [Full Text] [PDF]

				R. Pellegrino, A. Biggi, A. Papaleo, G. Camuzzini, J. R. Rodarte, and V. Brusasco Regional expiratory flow limitation studied with Technegas in asthma J Appl Physiol, November 1, 2001; 91(5): 2190 - 2198. [Abstract] [Full Text] [PDF]