Katherine A. Webb

The major limitation to exercise performance in COPD is dynamic hyperinflation

The inability to engage in sustained physical activity is a common feature of chronic obstructive pulmonary disease (COPD) and contributes importantly to the perception of poor health status. Given the vast pathophysiological heterogeneity of this disease, the concomitant effects of aging on

Combined physiological effects of bronchodilators and hyperoxia on exertional dyspnoea in normoxic COPD

Background: Studies examining the physiological interactions of oxygen (O2) and bronchodilators (BD) during exercise in chronic obstructive pulmonary disease (COPD) should provide new insights into mechanisms of exercise intolerance. We examined the effects of O2 and BD, alone and in combination, on dyspnoea, ventilation (V̇e), breathing pattern, operating lung volumes, and exercise endurance. Methods: In a randomised, double blind, crossover study, 16 patients with COPD (mean (SE) FEV1 43(3)% predicted) performed pulmonary function tests and an incremental exercise test, then completed four visits in which they received either nebulised BD (ipratropium 0.5 mg + salbutamol 2.5 mg) or placebo (PL) with either 50% O2 or room air (RA). After 90–105 minutes the patients performed pulmonary function tests, then breathed RA or O2 during symptom limited constant load exercise at 75% peak work rate. Results: With BD the mean (SE) increase in inspiratory capacity (IC) was 0.3 (0.1) l (p<0.05) at rest and during exercise, permitting greater tidal volume (Vt) expansion during exercise and a greater peak V̇e. With O2, V̇e decreased during exercise as a result of decreased breathing frequency (F), with no significant change in IC. During exercise with BD+O2, IC and Vt increased, F decreased, and V̇e did not change. Dyspnoea decreased with all interventions at a standardised time during exercise compared with PL+RA (p<0.05). Endurance time was significantly (p<0.05) greater with BD+O2 (10.4 (1.6) min) than with O2 (8.5 (1.4) min), BD (7.1 (1.3) min) and PL+RA (5.4 (0.9) min). Conclusion: By combining the benefits of BD (reduced hyperinflation) and O2 (reduced ventilatory drive), additive effects on exercise endurance were observed in patients with normoxic COPD.

Does dynamic hyperinflation contribute to dyspnoea during exercise in patients with COPD

Dynamic hyperinflation (DH) during exercise occurs in most but not all patients with advanced chronic obstructive pulmonary disease (COPD). It is not known whether the presence or absence of DH has implications for dyspnoea and exercise tolerance. Therefore, we compared detailed ventilatory and sensory responses to exercise in hyperinflators and nonhyperinflators with moderate-to-severe COPD. Nonhyperinflators (n=65) were retrospectively identified from a sample of 427 patients and case-matched to a group of hyperinflators (n=65) based on sex, age, body mass index and % predicted forced expiratory volume in 1 s. Resting pulmonary function and constant work rate cycle exercise responses were compared. Hyperinflators decreased inspiratory capacity (IC) from rest to peak exercise by 0.46±0.24 L whereas the nonhyperinflators increased IC by 0.10±0.15 L (p<0.0001). There were no significant group differences in endurance time (9.11±5.98 versus 8.87±5.24 min) or dyspnoea intensity for any given time or ventilation. An inflection in tidal volume versus ventilation occurred in the majority of nonhyperinflators (n=61) and hyperinflators (n=62) at a similar time and ventilation. Mechanical constraints on tidal volume expansion and the attendant rise in dyspnoea intensity were similar in both groups. Dyspnoea intensity during exercise was associated with progressive mechanical constraints on tidal volume expansion regardless of the presence of DH.

Evaluation of acute bronchodilator reversibility in patients with symptoms of GOLD stage I COPD

Background: Patients with symptoms of GOLD stage I chronic obstructive pulmonary disease (COPD) can have significant abnormalities of ventilatory mechanics with greater exertional symptoms and exercise limitation than age-matched healthy subjects. In such patients the impact of bronchodilator therapy remains unknown and is difficult to evaluate. Methods: The acute effects of nebulised ipratropium bromide 500 μg (IB) on resting pulmonary function and on dyspnoea and ventilatory parameters during symptom-limited constant work rate cycle exercise were measured. In a randomised double-blind crossover study, 16 patients with COPD (mean (SD) post-bronchodilator forced expiratory volume in 1 s (FEV1) 90 (7)% predicted, FEV1/forced vital capacity (FVC) 59 (7)%) with a significant smoking history (mean (SD) 44 (16) pack-years) inhaled either IB or placebo on each of two separate visits. Pulmonary function tests and cycle exercise at 80–85% of each subject’s maximal work capacity were performed 2 h after dosing. Results: Compared with placebo, FEV1 increased 5 (9)% predicted, residual volume decreased 12 (20)% predicted and specific airway resistance decreased 81 (93)% predicted (all p<0.05) after IB. At a standardised time during exercise, dynamic inspiratory capacity and tidal volume significantly increased in tandem by 0.12 and 0.16 litres, respectively (each p<0.05), dyspnoea fell by 0.9 (1.8) Borg units (p = 0.07) and dyspnoea/ventilation ratios fell significantly (p<0.05). The fall in dyspnoea intensity at higher submaximal ventilations correlated with the concurrent decrease in end-expiratory lung volume (p<0.05). Conclusion: In patients with symptoms of GOLD stage I COPD, IB treatment is associated with modest but consistent improvements in airway function, operating lung volumes and dyspnoea intensity during exercise. These results provide a physiological rationale for a trial of bronchodilator therapy in selected patients with milder but symptomatic COPD.

Decline of Resting Inspiratory Capacity in COPD: The Impact on Breathing Pattern, Dyspnea, and Ventilatory Capacity During Exercise

BACKGROUND To better understand the interrelationships among disease severity, inspiratory capacity (IC), breathing pattern, and dyspnea, we studied responses to symptom-limited cycle exercise in a large cohort with COPD. METHODS Analysis was conducted on data from two previously published replicate clinical trials in 427 hyperinflated patients with COPD. Patients were divided into disease severity quartiles based on FEV(1) % predicted. Spirometry, plethysmographic lung volumes, and physiologic and perceptual responses to constant work rate (CWR) cycle exercise at 75% of the peak incremental work rate were compared. RESULTS Age, body size, and COPD duration were similar across quartiles. As the FEV(1) quartile worsened (mean, 62%, 49%, 39%, and 27% predicted), functional residual capacity increased (144%, 151%, 164%, and 185% predicted), IC decreased (86%, 81%, 69%, and 60% predicted), and peak incremental cycle work rate decreased (66%, 55%, 50%, and 44% predicted); CWR endurance time was 9.7, 9.3, 8.2, and 7.3 min, respectively. During CWR exercise, as FEV(1) quartile worsened, peak minute ventilation (

Effects of BMI on Static Lung Volumes in Patients With Airway Obstruction

\dot{\mathrm{V}}

Sex differences in the perceived intensity of breathlessness during exercise with advancing age

e) and tidal volume (Vt) decreased, whereas an inflection or plateau of the Vt response occurred at a progressively lower