Am. J. Respir. Crit. Care Med., Vol 150, No. 2, 08 1994, 363-368.
Changes in residual volume during induced bronchoconstriction in healthy and asthmatic subjects
R Pellegrino, B Violante, R Selleri and V Brusasco
Servizio di Fisiopatologia Respiratoria, Ospedale A, Carle, Cuneo, Italy.
The increase of residual volume (RV) was investigated during acute
bronchoconstriction induced in healthy subjects by methacholine (MCh)
(Group 1, n = 13) and in asthmatics by MCh (Group 2, n = 21), or housemite
dust (Group 3, n = 11) during early and late airway responses (EAR and
LAR), or a series of deep breaths (Group 4, n = 7). In all subjects the
difference between residual volume after partial (RVp) and maximal maneuver
(RV), expressed as a percentage of control FVC, increased during
bronchoconstriction and was correlated with the percent increase of maximal
to partial flow ratio at 50% of control FVC (M/P50) (r = 0.854, p <
0.0001). At comparable reduction of partial expiratory flow at 50% of
control FVC (VP50), the decreases of FEV1 and FVC were less in healthy than
asthmatic subjects, whereas the change of FEV1/FVC was similar in all
groups, reflecting similar change in slope of flow-volume curves. The
increase of RVp was similar in all groups (range: 15 to 19%), but the
increase of RV was 6 +/- 1% (SEM) in healthy subjects and significantly
greater (range: 11.1 to 13.3%) in all groups of asthmatics (p < 0.02,
analysis of variance [ANOVA]). The effect of deep inhalation (DI) on the
airway caliber as assessed by the increase of M/P50 was higher in normal
subjects than in all groups of asthmatics (p < 0.0001). A negative
correlation was found between the increases of RV and M/P50 in all groups
(r = -0.358, p < 0.01), suggesting that healthy subjects had a limited
increase of RV because of a marked bronchodilator effect of DI.(ABSTRACT
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