Inspiratory muscle training in obstructive lung disease

Key points

• Dyspnoea is influenced by inspiratory muscle strength and the load placed upon the inspiratory muscles.

• Dynamic hyperinflation is a major cause of dyspnoea and exercise intolerance in patients with expiratory flow limitation due to its detrimental effect upon inspiratory muscle loading.

• Specific IMT improves inspiratory muscle strength, reduces dyspnoea and improves exercise tolerance, even in individuals without inspiratory muscle weakness or hyperinflation.

• Pressure threshold IMT is the most reliable, convenient and commonly used method of IMT, eliciting improvements in a wide range of muscle functional characteristics, including strength, shortening velocity, power and endurance.

• Inspiratory muscles adhere to the same training principles as other skeletal muscles, with respect to overload, specificity and reversibility.

• Training loads must exceed 30% of inspiratory muscle strength, with at least once daily training and weekly increases in training load. Programmes should be least 6 weeks in duration, after which frequency can be reduced to two sessions, three times per week.

• IMT can be implemented as a stand-alone intervention or as part of a comprehensive programme of rehabilitation.

• Monitored outcomes should include inspiratory muscle strength, an index of dyspnoea (e.g. BDI/TDI and/or Borg CR-10) and exercise tolerance (e.g. 6MWD).

Educational aims

• To provide an overview of the role of respiratory muscle function in the genesis of dyspnoea.

• To describe the response of inspiratory muscles to different types of training stimuli.

• To offer guidance on the implementation and monitoring of IMT.

Summary Dyspnoea is strongly influenced by respiratory muscle function. Patients with obstructive lung disease become hyperinflated and experience an associated functional deficit in inspiratory muscle function, as well as a concomitant increase in the work of breathing. These changes result in a heightened sense of respiratory effort and a propensity for inspiratory muscle fatigue. There is now convincing evidence that specific inspiratory muscle training (IMT) improves respiratory muscle function, reduces dyspnoea and improves exercise tolerance. This review will describe the two most commonly implemented methods of IMT, and the specific functional adaptations that are elicited by each. It will also describe successful, evidence-based implementation and monitoring of the most commonly used method of IMT.