No abstract

The purpose of this study was to examine potential contributing factors to breathlessness during bronchoconstriction, in particular, to evaluate the role of lung hyperinflation. We also wished to elucidate qualitative aspects of the unpleasant sensory experience and to identify factors that contribute to intersubject variability in subjective and objective assessments of airflow obstruction. We studied sensory-mechanical interrelationships during and after induced bronchoconstriction in 21 subjects with mild stable asthma. Breathlessness (Borg scale), spirometry, and inspiratory capacity (IC) were measured after each dose during methacholine bronchoprovocation to a maximal change (delta) in FEV1 of 50%. Breathing pattern, specific airway resistance (SRaw), plethysmographic thoracic gas volume, and maximal inspiratory mouth pressure (MIP) were recorded at baseline, at maximal response, and at full symptom recovery. End-expiratory lung volume (EELV) was derived from IC. Borg increased from 0.4 +/- 0.1 (very, very slight) at baseline to 5.0 +/- 0.5 (severe) at maximal bronchoconstriction (mean +/- SEM, p < 0.001). FEV1 fell significantly (p < 0.001) to 48% predicted at maximal response. Of the 21 subjects, 19 reported increased inspiratory rather than expiratory difficulty and predominantly described sensations of reduced inspiratory capacity and unrewarded inspiratory effort. Stepwise multiple regression analysis using delta Borg (outcome variable) versus changes in spirometry, SRaw, IC, and breathing pattern components, selected delta IC as the principal contributing factor: delta Borg = 0.09 (delta IC, %fall); n = 193, r = 0.86, p < 0.001. delta IC continued to contribute significantly (p < 0.001) to the variance in Borg ratings after accounting for delta FEV1, and it was the strongest predictor of symptom recovery (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of bronchodilator responses in patients with 0irreversible0 emphysema. D.E. O9Donnell, L. Forkert, K.A. Webb. #ERS Journals Ltd 2001. ABSTRACT: Given the emerging physiological and clinical rationale for pharmacological lung-volume reduction, assessment of volume responses to bronchodilators is likely to be highly relevant in chronic obstructive pulmonary disease (COPD). The authors examined the magnitude of lung-volume reduction after acute bronchodilator treatment in patients with advanced emphysema.Eighty-four stable patients with emphysema (mean¡SEM forced expiratory volume in one second (FEV1): 32¡1% predicted) performed spirometry and body plethysmography before and 15-30 min after 200 mg salbutamol. Only irreversible patients with a postbronchodilator change in FEV1 v10% pred were considered in this study.Postsalbutamol, the majority of subjects (83%) had significant improvements in one or more lung volumes: on average, residual volume (RV), functional residual capacity (FRC), inspiratory capacity (IC), forced vital capacity and slow vital capacity changed by -18¡2, -10¡1, 8¡1, 9¡1 and 7¡1% pred (pv0.0005 each). Total lung capacity (TLC) decreased 0.12¡0.04 L (pv0.01). Change in IC reflected change in FRC (r=-0.60, pv0.0005), but more strongly in the 57% of patients with no significant change in TLC (r=-0.93, pv0.0005). The magnitude and frequency of volume responses were greatest in patients with the most severe COPD; for example, RV decreased by 0.51¡0.09 L (23¡4% pred) and 0.27¡0.04 L (14¡2% pred) in severe and moderate subgroups, respectively.Significant reductions in lung hyperinflation occurred in the absence of a change in forced expiratory volume in one second after low-dose salbutamol in a majority of patients with advanced emphysema; the greatest changes occurred in those with the most severe disease. The relatively diminished bronchodilator response in chronic obstructive pulmonary disease (COPD) (compared with asthma) has led to its designation as an irreversible airways disease and has, consequently, promoted a general attitude of therapeutic nihilism. Although the measurement of maximal flow rates e.g. the forced expiratory volume in one sec (FEV1) is of unquestionable diagnostic utility, and has become an acceptable (albeit imprecise) measure of disease severity in COPD, recent studies have shown that this measurement has definite limitations as a clinical outcome measure for the evaluation of bronchodilator efficacy [1][2][3][4]. In advanced COPD, forced expiratory manoeuvres initiated from total lung capacity (TLC) are fraught with measurement artefact (e.g. gas and airway compression effects) that underestimate the true maximal expiratory flows available over the operating tidal volume range [5]. Therefore, FEV1, only crudely reflects the degree of expiratory-flow limitation (EFL), which is the true pathophysiological hallmark of COPD [6]. The FEV1 correlates weakly, or not at all, with symptom intensity and exercise capacity in COPD [7][8][9].A major consequence of EFL is air...

The natural history of lung hyperinflation in patients with airway obstruction is unknown. In particular, little information exists about the extent of air trapping and its reversibility to bronchodilator therapy in those with mild airway obstruction. We completed a retrospective analysis of data from individuals with airway obstruction who attended our pulmonary function laboratory and had plethysmographic lung volume measurements pre-and post-bronchodilator (salbutamol). COPD was likely the predominant diagnosis but patients with asthma may have been included. We studied 2,265 subjects (61% male), age 65 ± 9 years (mean ± SD) with a postbronchodilator FEV 1 /FVC <0.70. We examined relationships between indices of airway obstruction and lung hyperinflation, and measured responses to bronchodilation across subgroups stratified by GOLD criteria. In GOLD stage I, vital capacity (VC) and inspiratory capacity (IC) were in the normal range; pre-bronchodilator residual volume (RV), functional residual capacity (FRC) and specific airway resistance were increased to 135%, 119% and 250% of predicted, respectively. For the group as a whole, RV and FRC increased exponentially as FEV 1 decreased, while VC and IC decreased linearly. Regardless of baseline FEV 1 , the most consistent improvement following bronchodilation was RV reduction, in terms of magnitude and responder rate. In conclusion, increases (above normal) in airway resistance and plethysmographic lung volumes were found in those with only minor airway obstruction. Indices of lung hyperinflation increased exponentially as airway obstruction worsened. Those with the greatest resting lung hyperinflation showed the largest bronchodilator-induced volume deflation effects. Reduced air trapping was the predominant response to acute bronchodilation across severity subgroups.