Why Inspiratory Muscle Training (IMT)?

Primary weakness of the inspiratory muscles, as well as the effects of static and dynamic hyperinflation, secondary to airway obstruction, induce weakening of inspiratory muscles, as well as increasing the elastic work of breathing. The resulting neuromechanical dissociation (an imbalance between demand and capacity) intensifies the sensation of dyspnea. See extract from ‘Respiratory Muscle Training: Theory and Practice’ (McConnell, 2013) for a comprehensive description.

Furthermore, a recent review by O’Donnell and colleagues (O’Donnell, Milne, James, de Torres, & Neder, 2019) provides an authoritative, up-to-date overview of the mechanisms contributing to dyspnea in patients with COPD. They conclude that:

“A common final pathway of dyspnea relief and improved exercise tolerance across the range of therapeutic interventions (bronchodilators, exercise training, ambulatory oxygen, inspiratory muscle training, and opiate medications) is reduced neuromechanical dissociation of the respiratory system”.

Evidence supporting IMT for patients with COPD

The strongest and most robust form of evidence is that derived using systematic review and meta-analysis. The most recent of these for IMT and COPD was published in 2018 (Beaumont, Forget, Couturaud, & Reychler, 2018). Based on their analysis of 43 studies, Beaumont and colleagues concluded that:

“IMT using threshold devices improves inspiratory muscle strength, exercise capacity and quality of life, decreases dyspnea.”

In addition, a recent physiological study from the laboratory of O’Donnell examined the effect of IMT upon diaphragm activation and exertional dyspnea (Langer et al., 2018), demonstrating the basis for the physiological mechanisms underpinning the benefits of IMT. The study showed that,

“8 weeks of home-based, partially supervised IMT improved respiratory muscle strength and endurance, dyspnea, and exercise endurance. Dyspnea relief occurred in conjunction with a reduced activation of the diaphragm relative to maximum in the absence of significant changes in ventilation, breathing pattern, and operating lung volumes”.

See also the evidence cited by O’Donnell and colleagues in their 2019 analysis of underlying mechanisms (O’Donnell et al., 2019).

Evidence supporting IMT for patients with asthma

There has been far less research on the effects of IMT with patients who have asthma. A 2013 Cochrane systematic review (Silva et al., 2013) concluded that,

“There is no conclusive evidence in this review to support or refute inspiratory muscle training for asthma. The evidence was limited by the small number of trials with few participants..”.

Notwithstanding, there are several similarities between the neuromechanical mechanisms intensifying dyspnea in acute asthma and in COPD. Accordingly, it is reasonable to suggest that, for at least some people with asthma, IMT will have the same benefits as have been shown for patients with COPD (Beaumont et al., 2018; O’Donnell et al., 2019). Furthermore, based on the observation that,

“IMT has been shown to decrease dyspnea, increase inspiratory muscle strength, and improve exercise capacity in asthmatic individuals”, a 2016 narrative review (Shei, Paris, Wilhite, Chapman, & Mickleborough, 2016) recommended that: “In order to develop more concrete recommendations regarding IMT as an effective low-cost adjunct in addition to traditional asthma treatments, we recommend that a standard treatment protocol be developed and tested in aplacebo controlled clinical trial with a large representative sample”.

The most recent randomized controlled trial of IMT with patients who have asthma (Duruturk, Acar, & Dogrul, 2018) concluded: “These findings suggest that IMT may be an effective modality to enhance respiratory muscle strength, exercise capacity, quality of life, daily living activities, reduced perception of dyspnea, and fatigue in asthmatic patients”.

Relevant medical studies:

Effects of inspiratory muscle training in COPD patients: A systematic review and meta-analysis (2018).

Effect of Inspiratory Muscle Training in the Management of Patients With Asthma: A RANDOMIZED CONTROLLED TRIAL (2018)

Inspiratory muscle training reduces diaphragm activation and dyspnea during exercise in COPD (2018)

Respiratory Muscle Training: Theory and Practice (2013)

Dyspnea in COPD: New Mechanistic Insights and Management Implications. (2019)

The role of inspiratory muscle training in the management of asthma and exercise-induced bronchoconstriction. (2016)

Inspiratory muscle training for asthma. (2013)

References:

Beaumont, M., Forget, P., Couturaud, F., & Reychler, G. (2018). Effects of inspiratory muscle training in COPD patients: A systematic review and meta-analysis. Clin Respir J, 12(7),2178-2188. doi:10.1111/crj.12905

Duruturk, N., Acar, M., & Dogrul, M. I. (2018). Effect of Inspiratory Muscle Training in the Management of Patients With Asthma: A RANDOMIZED CONTROLLED TRIAL. J Cardiopulm Rehabil Prev, 38(3), 198-203. doi:10.1097/HCR.0000000000000318

Langer, D., Ciavaglia, C., Faisal, A., Webb, K. A., Neder, J. A., Gosselink, R., . . . O’Donnell, D. E. (2018). Inspiratory muscle training reduces diaphragm activation and dyspnea during exercise in COPD. J Appl Physiol (1985), 125(2), 381-392. doi:10.1152/japplphysiol.01078.2017

McConnell, A. K. (2013). Respiratory Muscle Training: Theory and Practice (1st ed.). Oxford: Churchill Livingstone.

O’Donnell, D. E., Milne, K. M., James, M. D., de Torres, J. P., & Neder, J. A. (2019). Dyspnea in COPD: New Mechanistic Insights and Management Implications. Adv Ther. doi:10.1007/s12325-019-01128-9

Shei, R. J., Paris, H. L., Wilhite, D. P., Chapman, R. F., & Mickleborough, T. D. (2016). The role of inspiratory muscle training in the management of asthma and exercise-induced bronchoconstriction. Phys Sportsmed, 44(4), 327-334.doi:10.1080/00913847.2016.117654

Silva, I. S., Fregonezi, G. A., Dias, F. A., Ribeiro, C. T., Guerra, R. O., & Ferreira, G. M. (2013). Inspiratory muscle training for asthma. Cochrane Database Syst Rev(9), CD003792. doi:10.1002/14651858.CD003792.pub2