Inspiratory muscle training

Abstract

The respiratory pump is at the center of the ventilatory system and ensures supply and removal of respiratory gases. Proper functioning of the pump depends on a delicate balance between its capacity and the load exerted on it. Impairments in diaphragmatic and non-diaphragmatic inspiratory muscle function can distort this balance and can lead to an overloading of the pump. In the context of pulmonary rehabilitation (PR) the respiratory muscles are of key importance during physical exertion. Increasing ventilatory needs by performing physical exercises or daily activities acutely increase the load on the respiratory muscles. The resulting load-capacity imbalance can contribute to symptoms of exertional dyspnea and exercise limitation. Respiratory muscle dysfunction is observed in many candidates for PR. The benefits of respiratory rehabilitation programs in patients with chronic obstructive pulmonary disease (COPD) are well established. PR leads to statistically significant and clinically relevant improvements in exercise tolerance and health-related quality of life. The role of training the respiratory muscles in respiratory rehabilitation remains however still controversial after more than 40 years of research. Current guidelines and meta-analyses are not unequivocally positive on the additional value of inspiratory muscle training (IMT) as a program component of a respiratory rehabilitation program. From the most recent meta-analysis in patients with COPD it was concluded that IMT can improve inspiratory muscle strength and endurance, functional exercise capacity, dyspnea and quality of life when applied as a stand-alone intervention. Additional benefits beyond improvements in respiratory muscle function have however not consistently been demonstrated when IMT was studied as an "add-on" intervention to general exercise training. In patients with more pronounced inspiratory muscle weakness, the addition of IMT to a general exercise training program tended to improve exercise performance more than in patients with better preserved respiratory muscle function. The current evidence is however inconclusive as to who might benefit most from additional respiratory muscle training as part of their PR program. This chapter will present available training methods and will discuss their applicability, usefulness, and effectiveness as rehabilitation tools in participants of PR programs.