Dyspnea In Chronic Obstructive Pulmonary Disease Research Articles

Dyspnoea in COPD: Can inspiratory muscle training help?

Chronic obstructive pulmonary disease (COPD) is a progressive, common and costly condition. Dyspnoea frequently limits activity and reduces health-related quality of life. In addition to impaired lung function, peripheral muscle deconditioning and respiratory muscle dysfunction also contribute to dyspnoea and reduced exercise capacity. Pulmonary rehabilitation using whole body exercise training improves peripheral muscle function and reduces dyspnoea but does not improve respiratory muscle function. Providing that adequate training intensities are utilised, specific loading of the inspiratory muscles with commercially available hand-held devices can improve inspiratory muscle strength and endurance. Several studies have investigated the effects of inspiratory muscle training on dyspnoea in COPD subjects. Results of these studies are conflicting, most likely reflecting methodological shortcomings including insufficient training load, insensitive outcome measures, and inadequate statistical power. This paper describes the origin of dyspnoea in COPD, with particular attention given to the role of inspiratory muscle dysfunction in its genesis and its possible amelioration through inspiratory muscle training.

Chronic exertional dyspnea and respiratory muscle function in patients with chronic obstructive pulmonary disease.

The symptom of breathlessness is an important outcome measure in the management of patients with chronic obstructive pulmonary disease (COPD). Clinical ratings of dyspnea and routine lung function are weakly related to each other. However, in the clinical setting breathlessness in COPD is encountered under conditions of increased respiratory effort, impeded respiratory muscle action, or functional weakness. Thus, the present study was carried out to determine whether and to what extent clinical ratings of dyspnea and respiratory muscle dysfunction relate to each other. In 21 patients with COPD two methods were used to rate dyspnea: a modified Medical Research Council Scale (MRC) and the Baseline Dyspnea Index (BDI), which is a multidimensional instrument for measuring dyspnea based on three components: magnitude of task, magnitude of effort, and functional impairment. A baseline focal score was obtained as the sum of the three components. Measures were: pulmonary volumes; arterial blood gases; maximal voluntary ventilation (MVV); maximal inspiratory and expiratory pressures (MIP and MEP, respectively); and breathing patterns ventilation (VE), tidal volume (VT), and respiratory frequency (Rf). In 15 patients pleural pressure was also measured during both quiet breathing (Pplsw) and maximal inspiratory sniff maneuver at FRC (Pplsn). BDI and MRC ratings related to each other and showed comparable weak associations with standard parameters (FEV1, PaCO2, VT), MIP, and MEP. In contrast, MVV closely and similarly related to both ratings. Pplsw (%Pplsn), a measure of respiratory effort, and Pplsw (%Pplsn)/VT(%VC), an index of neuroventilatory dissociation, related significantly to both the BDI (r2 = -0.77 and r2 = -0.75, respectively) and the MRC (r2 = 0.81 and r2 = 0.74, respectively). Using MVV, Pplsw (%Pplsn), and Pplsw (%Pplsn)/VT(%VC) in a stepwise multiple regression as independent variables with BDI rating as dependent variable, MVV explained an additional 14.5% of the variance of the BDI over the 67.8% predicted by Pplsw (%Pplsn). Our results demonstrate that the level of chronic exertional dyspnea in COPD increases as the ventilatory muscle derangement increases. The level of the relationships among dyspnea ratings and MVV and respiratory effort helps to explain some of the mechanisms of chronic dyspnea of COPD. These measures should be considered for therapeutic intervention to reduce dyspnea.

The Role of Theophylline in the Treatment of Dyspnea in COPD

Dyspnea is influenced by both physiologic and psychologic factors. Breathlessness is common in patients with chronic obstructive pulmonary disease (COPD) and often is the reason that the individual patient seeks medical attention. In order to evaluate the different clinical studies involving the use of theophylline in COPD patients, it is important to consider the three distinct approaches for measuring dyspnea--psychophysical testing, clinical methods, and ratings during exercise. Four randomized, double-blind, placebo-theophylline trials from one to four weeks in duration have evaluated the impact of theophylline on lung function and breathlessness. In these studies, the overall improvement in forced expiratory volume in one second was quite consistent for theophylline compared with placebo therapy. When appropriate clinical methods for measuring dyspnea were used, theophylline showed a positive reduction in breathlessness. These reports suggest that theophylline provides modest objective and subjective improvement in patients with symptomatic chronic air flow obstruction.