Breathlessness (apnea) and underlying hypertension issues are the troublesome aspects of OSA that result in poor quality of life and may cause mortality due to cardiovascular problems.
The available treatments for OSA are continuous positive airway pressures (CPAP), surgical interventions, and oral or nasal devices – all of them are neither cost-effective nor easy to handle.
Instead of these complex interventions, there is an emerging body of evidence on respiratory muscle training (RMT) for its effectiveness in OSA.
Two teams of researchers independently evaluated the effects of inspiratory muscle training (IMT), a type of RMT, on OSA patients in two different meta-analyses. One meta-analysis included 7 studies with more than 250 participants and the second meta-analysis included 7 studies with 160 participants. Both meta-analyses revealed that RMT effectively improves pulmonary function, hypertension, and sleep quality in OSA patients.
OSA: A widespread concern with severe health implications
OSA is a sleep disorder that occurs due to the obstruction of the upper airways and causes complete breathlessness or shortness of breath while sleeping [1]. The risk factors of OSA are similar to those of cardiovascular diseases and OSA is associated with increased cardiovascular morbidity and mortality [2], [3], [4]. About 50% of OSA patients have hypertension issues [5]. The global prevalence of OSA ranges from 9% to 38%, which are alarming levels [6].
How obstructive sleep apnea impacts breathing and heart health
The labored breathing due to obstructed airways in OSA puts pressure on inspiratory muscles leading to weakness and decreased functioning of these muscles [7]. These factors cause poor lung functioning during sleep, asphyxia, poor sleep quality, and daytime sleepiness which results in arterial stiffness via increased oxidative stress, sympathetic activation, and endothelial dysfunction, thus increasing the chances of cardiovascular problems in OSA patients [8].
Treatment options for OSA
CPAP is considered a primary treatment for OSA in which air is provided at a pressure that ensures the opening of airways to provide continuous and effortless breathing. Moreover, some surgical interventions and oral or nasal devices have also been introduced for the treatment of OSA.
However, there is less compliance of OSA patients with these treatments as these are not cost-effective, difficult to maintain, and may cause complications.
Recently, the use of RMT devices has been found effective in improving respiratory muscle strength and performance, blood pressure, and sleep quality in OSA patients.
Clinical evidence from 7 studies showing the effect of RMT on OSA patients
Two independent teams of 10 researchers have evaluated the effect of IMT on OSA patients in two different meta-analyses. The first team from Jamia Millia Islamia, Centre for Physiotherapy and Rehabilitation Sciences, New Delhi, India consisted of three researchers who investigated 953 studies to find the effects of IMT in OSA patients. They selected 7 studies with varying numbers of participants (more than 250 participants in all studies) to assess the effect of IMT on OSA [9].
The second team, including 7 researchers from Taiwan and Landon, screened 126 publications to evaluate the effects of IMT on blood pressure and sleep quality in OSA patients and they selected 7 studies with 160 patients for their meta-analysis [10].
All the studies selected for these meta-analyses were randomized control trials (RCTs). The researchers conducted meta-analyses on the effects of IMT on inspiratory muscle strength, the severity of disease, sleep quality, daytime sleepiness, lung function, exercise capacity, blood pressure, and plasma catecholamine levels (because these have effects on heart rate and blood pressure) in mild to severe OSA patients.
How RMT is beneficial for patients with OSA
Six studies assessed the effect of IMT on sleep quality in one meta-analysis and 5 studies in the second meta-analysis. Both of these meta-analyses individually reported a significant improvement in the sleep quality of OSA patients by IMT. 4 studies assessed the effect of IMT on daytime sleepiness in one meta-analysis and 3 studies in the second meta-analysis, and both of these meta-analyses showed a significant decrease in daytime sleepiness by IMT.
Six studies reported inspiratory muscle strength in one meta-analysis and 3 studies in the second meta-analysis. Both meta-analyses showed a significant improvement in inspiratory muscle strength by IMT. For lung function assessment, 3 studies were assessed in one meta-analysis and the researchers found that IMT had moderate to significant improvement in lung function in OSA patients.
In the second meta-analysis, 3 studies analyzed systolic and diastolic blood pressures. The meta-analysis of these studies showed that systolic and diastolic blood pressures were significantly lower in the IMT group than in the control group after the training period. The analysis of two studies showed that plasma levels of catecholamines were significantly lower in the IMT group than in the control group.
Conclusion
RMT is effective in relieving short-term symptoms in OSA patients by improving inspiratory muscle strength, lung function, and quality of sleep, and decreasing blood pressure, serum levels of catecholamines, and daytime sleepiness.
References
[5] M. Ahmad, D. Makati, and S. Akbar, “Review of and Updates on Hypertension in Obstructive Sleep Apnea,” Int. J. Hypertens., vol. 2017, Sep. 2017, doi: 10.1155/2017/1848375.
[10] T.-A. Chen et al., “Effects of inspiratory muscle training on blood pressure- and sleep-related outcomes in patients with obstructive sleep apnea: a meta-analysis of randomized controlled trials,” Sleep Breath., Dec. 2022, doi: 10.1007/s11325-022-02773-1.