COPD patients undergo changes in the musculoskeletal system, which leads to decreased functional capacity and reduced quality of life.
Although there is no definite treatment for COPD, some drugs, exercises, and respiratory muscle training (RMT) are used in combination to provide relief to COPD patients. RMT is effective for COPD patients in improving dyspnea (shortness of breath), functional capacity, and breathing muscle strength.
However, the question of the most effective RMT protocol, training loads, and standardized devices remains a matter of debate for COPD patients. This is due to the reason that every study uses different RMT devices with varying protocols and training loads.
This systematic review [1] aimed to find the answer to this question by analyzing all the studies published in the last 10 years that applied RMT devices in COPD patients.
What is COPD?
COPD is the progressive narrowing of airways due to the chronic inflammation of lung tissue. According to the World Health Organization (WHO), this disease was the third major cause of mortality in 2019, with a total of 3.23 million deaths worldwide [2].
It is characterized by breathlessness, labored breathing, and exercise intolerance due to the lack of elasticity and functionality of the diaphragm (the main respiratory muscle) and lungs in response to hyperinflammation in COPD.
The diaphragm needs to put in extra effort to maintain the negative pressure in the chest cavity, and, as a result, it loses its characteristic dome shape. Thus, the diaphragm cannot work properly during inspiration and expiration, leading to the accumulation of carbon dioxide in the circulation [3] [4].
Treatment options for COPD patients
The treatment of COPD involves both pharmacological and non-pharmacological approaches, followed by monitoring treatment outcomes to adjust the management strategies accordingly [5]. Breathing exercises are an important non-pharmacological approach for COPD patients [6].
RMT using RMT has been found effective in improving various symptoms of COPD patients, including dyspnea, functional capacity, and inspiratory muscle strength.
Systematic review: Different RMT devices, loads and protocols in COPD patients
The researchers from Sao Paulo, Brazil, conducted a systematic review to determine the best effective RMT protocol and training load for COPD patients. They screened 1,803 studies published in 10 years and ultimately selected 10 studies for this systematic review and checked the reporting quality of included studies. [1]
The researchers reviewed the devices used for RMT, the RMT protocol, and training loads applied in these studies. Respiratory muscle strength and endurance of respiratory muscles were measured by MIP and maximal voluntary ventilation (MVV) in 398 COPD patients from these studies worldwide.
Moreover, the cardiorespiratory fitness and functional capacity were measured by maximal oxygen consumption, inspiratory time with submaximal load, maximum distance covered in a 6-minute walk, and sleep quality.
Different RMT devices, loads, and protocols for COPD patients
This review of 10 clinical studies provided insights into the most widely used RMT device among the studies included in this review, along with the frequently used RMT load and protocol for COPD patients.
RMT Devices
The most commonly used devices were Threshold and POWERbreathe. The Threshold was used in almost all studies, suggesting that this was the most popular device among all the studies.
RMT load and protocol
Nine studies used RMT at the load of 30%-80% of the initial value of MIP and the load was adjusted every one or two weeks in 8 of these 9 studies. The studies where an RMT load of 60-80% was used showed slightly higher improvements in COPD patients than the studies where an RMT load of 35-50% was used.
The RMT treatment time in all studies ranged between 4-12 weeks.
Effect of RMT in COPD patients
This review showed that RMT in COPD patients improved breathing muscle strength (measured with maximum inspiratory pressure).
Of the 10 studies, 4 studies reviewed the effect of RMT on the maximum distance covered in a 6-minute walk and 3 of them showed there was a significant increase in the distance covered in the 6 minutes by those COPD patients who received RMT.
Two studies measured the endurance of inspiratory muscles by inspiratory time with submaximal load and all the patients in these studies showed a significant improvement in this test after RMT.
Four studies evaluated the effect of RMT on sleep quality and 3 of them showed that RMT improved sleep quality in COPD patients.
Discussion on the results
All studies used the RMT devices with an initial load of 30-80% of MIP. RMT improved respiratory muscle strength and endurance, cardiorespiratory fitness, functional capacity, and sleep quality in COPD patients.
Regarding the duration of the training period, similar results have been reported by a previous systematic review, including 48 studies [7].
Another systematic review of 43 studies presented similar results in improving the inspiratory muscle strength and functional capacity by RMT in COPD patients [8].
Conclusions
The Threshold device was the widely used RMT device in these studies with loads of 30-80%. RMT improved inspiratory muscle strength, functional capacity, and sleep quality in COPD patients.
The best RMT protocol for COPD patients has not yet been established.
References
[1]. E. de D. P. e. C. U. no T. M. I. de indivíduos com DPOC: uma revisão sistemática, “Effectiveness of different protocols and loads used in inspiratory muscle training of individuals with COPD: a systematic review,” doi: 10.1590/1809-2950/22004529032022EN.
[7]. R. I. N. Figueiredo, A. M. Azambuja, F. V. Cureau, and G. Sbruzzi, “Inspiratory Muscle Training in COPD,” Respir. Care, vol. 65, no. 8, pp. 1189–1201, Aug. 2020, doi: 10.4187/respcare.07098. [Online]. Available: https://rc.rcjournal.com/content/65/8/1189.short.
