PT  - JOURNAL ARTICLE
AU  - C Tantucci
AU  - M Ellaffi
AU  - A Duguet
AU  - M Zelter
AU  - T Similowski
AU  - JP Derenne
AU  - J Milic-Emili
TI  - Dynamic hyperinflation and flow limitation during methacholine-induced bronchoconstriction in asthma
AID  - 10.1183/09031936.99.142
DP  - 1999 Aug 01
TA  - European Respiratory Journal
PG  - 295--301
VI  - 14
IP  - 2
4099  - http://erj.ersjournals.com/content/14/2/295.short
4100  - http://erj.ersjournals.com/content/14/2/295.full
SO  - Eur Respir J1999 Aug 01; 14
AB  - 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.