The role of inspiratory muscle function and training in the genesis of dyspnoea in asthma and COPD

Abstract

SummaryThe cardinal symptom of both asthma and COPD is dyspnoea, and from a patient perspective, the most troublesome. There are a multitude of inputs to the sensation of dyspnoea, few of which are readily modifiable. The level of inspiratory muscle work contributes to the sense of respiratory muscle effort and thence dyspnoea. Inspiratory muscle work is elevated in patients with COPD and asthma due to hyperinflation and an increased ventilatory requirement for exercise. Treatment tends to concentrate on reducing the load upon the inspiratory muscles induced by hyperinflation. Bronchodilators are the mainstay of treatment for COPD and asthma; they reduce hyperinflation, inspiratory muscle loading and dyspnoea. In addition, programmes of pulmonary rehabilitation have an excellent evidence base for improving dyspnoea, exercise tolerance and quality of life. However, provision within the NHS is limited and not all patients are suitable. One component of pulmonary rehabilitation that can be implemented safely in a home-based setting is specific inspiratory muscle training (IMT). There is a strong theoretical rationale for IMT in patients with airway obstruction, which is also supported by empirical evidence. IMT offers a relatively accessible non-pharmacological treatment for dyspnoea that also improves exercise tolerance and quality of life.

Within-Breath Analysis of Respiratory Mechanics in Asthmatic Patients by Forced Oscillation

“…Therefore, although the total mechanical load of the breathing system is increased during the whole cycle (Figure 2A), it is likely that such a phenomenon is more evident during the inspiratory phase. This finding, associated with that described by McConnell and Alison33 that the sensation most clearly related to exercise intolerance in asthmatics is respiratory effort, emphasizes the relevance of muscular therapeutic interventions in these patients.…”

Cardiopulmonary responses of asthmatic children to exercise: Analysis of systolic and diastolic cardiac function

“…25 Asthmatic children have lower exercise tolerance because they have lower lung capacity during hard exercise which is the result of impaired diffusion of gases at the lung surface due to airway collapse caused by contraction of the diaphragm and increased pleural pressures generated to overcome airway obstruction. [26][27][28][29][30][31] These children may become hyperinflated during exercise and this reduces their tidal volume, ultimately affecting their ability to exchange gases. Impaired gas exchange due to pressure differences, insufficient surface area increased transit time of red blood cells and platelets and insufficient alveolar ventilation-perfusion results in rapid development of dyspnea during exercise, and thus limits physical capacity.…”

Respiratory Muscle Training Improves Speech and Pulmonary Function in COPD Patients in a Home Health Setting - a Pilot Study

“…Approximately 19% of patients with moderate to severe COPD experience acute exacerbations, which are critical episodes of the disease requiring immediate care and hospitalization. In high-income countries, COPD is the third leading cause of death, causing 3.8% of all deaths [1] [2] [4] [3] . Treatment strategies for COPD include bronchodilators and rehabilitation to improve exercise capacity.…”