The prevalence of chronic obstructive pulmonary disease (COPD) is 11.7% around the world, and it is expected to rise over the next 30 years. In Taiwan, COPD is estimated as the seventh leading cause of death in 2016, and has been gradually increasing in the past decades. COPD has been long considered to be a disease state characterized by airflow limitation that are not fully reversible, leading to abnormalities in control of breathing, worsening of respiratory mechanics and pulmonary function. However, COPD is no longer considered to affect only the lungs and airways, but also the rest of the body including decreases in respiratory and limb-muscle mass and function. When acute exacerbation occurs, lung function decreases rapidly. According to the previous studies, inspiratory muscle training (IMT), can improve the strength and endurance of the diaphragm, reduce dyspnea and breathing pattern, thus increasing the capacity of activities tolerance in patients with COPD. Although more and more studies are focus on diaphragm weakness and the effect of IMT in patients with COPD, the efficacy and intensity of IMT in patients with COPD is still controversial and the clinical use is limited. Whether increases intensity during IMT would lead to improvements in contraction pattern of respiratory muscle remained unclear. Therefore, the purpose of this study is to assess the activation patterns of diaphragm and sternocleidomastoid (SCM) muscle during different loaded inspiratory muscle performance in patients with COPD after acute exacerbation.
