By Julia O’Shea, RRT
Training the very muscles responsible for breathing might seem like an obvious addition to pulmonary rehab (PR). Weak inspiratory muscles contribute to breathlessness, after all. Yet inspiratory muscle training (IMT) remains underutilized in PR programs.
Its efficacy has been debated for decades, with research yielding mixed conclusions. For example, a 2023 Cochrane meta-analysis comparing IMT as an adjunct to PR versus IMT alone questioned whether the technique truly enhances PR outcomes. Since PR is already highly effective, additional interventions may not always demonstrate significant added benefits.
This article aims to explore IMT’s potential benefits with COPD and the physiology of breathlessness.
The Brain and Breathing
The brain regulates breathing for optimal comfort through its respiratory center, integrating inputs from the motor center, muscles, and cardiovascular system. Its goal is to respond efficiently, ensuring ease and minimizing stress.
Before discussing COPD, let's review normal breathing physiology during exercise:
As exercise intensity rises, the volume or size of the breath increases, followed by an increase in respiratory rate (times per minute we breathe). Eventually, volume levels off, and the respiratory rate continues to rise to meet the demands. As the lung elasticity decreases (think of a stiff, inflated balloon), inspiratory muscles work harder, contributing to breathing discomfort. These muscles signal the brain to increase breathing rate instead of volume. Ideally, the system balances the respiratory rate and volume to be able to sustain the effort. The volume is crucial for overcoming anatomical dead space, the part of the lungs that don’t participate in the exchange of oxygen and carbon dioxide (think upper chest and airways). Shallow breaths, which reduce volume and increase the respiratory rate, limit the exchange of these gases.
In COPD, the hyperinflation component causes trapped air (stiff balloon), forcing inspiratory muscles to work harder due to reduced chest elasticity and mobility. As breathing demand rises, muscles fatigue quickly, leading to breathlessness. With limited volume available, breathing becomes fast and shallow, limiting the exchange of oxygen and carbon dioxide. This, combined with poor aerobic fitness and peripheral muscle abnormalities, can lead to rapid lactic acidosis, further increasing the breathing demand and discomfort during exercise.
IMT enhances inspiratory muscle strength and endurance, similar to peripheral muscle training, where muscle fibers adapt to training loads. This may reduce dyspnea and improve exercise comfort in COPD.
Considerations for IMT in COPD
Patient Prioritization:
- PR participants with weak inspiratory muscles: Maximum Inspiratory Pressure (MIP) < 70% predicted
- Patients with dyspnea as their main limiting factor
- Motivated individuals aiming to maximize rehab benefits
Protocol Guidelines:
- No definitive best program; common protocols use 30%-50% of MIP
- Typical dosage: 30 breaths, twice daily, for 5-10 minutes
- Encourage full tidal volume and vital capacity inspirations with strong, deep breaths
Breathing Mechanics & Education:
- Assess the need for rib cage and thoracic spine mobility work
- Teach breathing pattern awareness (diaphragmatic breathing, lateral rib movement, upper chest control)
- Consider bronchodilators and pursed-lip breathing to support exhalation between training breaths
Integration Into Rehab:
- Can be a stand-alone therapy or part of a PR program
- Initiate before PR for those waiting to start or those with severe deconditioning
- Include in home exercise routines alongside PR
Outcome Measures:
- Assess dyspnea pre/post and during exercise
- Regular inspiratory muscle testing to track progress
The Future of IMT and COPD
What is clear, is that pulmonary rehab delivers optimal respiratory muscle training. The question is whether the quality of that training can be enhanced even further. With improving study quality, IMT is gaining recognition as a valuable adjunct to PR. Advancements in technology and electronic devices allow for better monitoring of training progress and quality. This could enhance adherence, optimize patient outcomes, and further support the expansion of pulmonary rehab programs.
REFERENCES:
- Ammous O, Feki W, Lotfi T, Khamis AM, Gosselink R, Rebai A, Kammoun S. Inspiratory muscle training, with or without concomitant pulmonary rehabilitation, for chronic obstructive pulmonary disease (COPD). Cochrane Database Syst Rev. 2023 Jan 6;1(1):CD013778. doi: 10.1002/14651858.CD013778.pub2. PMID: 36606682; PMCID: PMC9817429.
- McConnell, Alison. Breathe Strong, Perform Better. Human Kinetics, 2011.
Julia O’Shea, RRT, is the Pulmonary Rehab Coordinator at the University of Vermont Medical Center in Winooski Vermont. She has a special interest in assessment and treatment of breathing pattern disorders. Julia O’Shea has studied the Buteyko Breathing Method, and she is a certified practitioner of the BradCliff Breathing Method.