Activation Patterns of Diaphragm and Sternocleidomastoid Muscle during Threshold Loaded Breathing in Patients with Chronic Obstructive Pulmonary Disease

• Main Authors: Chien-Tzu Lee, 李建慈
• Other Authors: Li-Ying Wang
• Format: Others
• Language: en_US
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/6vmsnw

碩士 === 國立臺灣大學 === 物理治療學研究所 === 107 === Background and purpose: Inspiratory muscle weakness has been shown in patients with chronic obstructive pulmonary disease (COPD), and inspiratory muscle training (IMT) is commonly applied to these patients. In healthy adults, the accessory inspiratory muscles would be recruited during IMT along with the primary inspiratory muscle. In patients with COPD, the activation patterns of diaphragm and accessory inspiratory muscles during threshold loaded breathing has not been investigated. Therefore, the purpose of this study was to exam diaphragm and sternocleidomastoid (SCM) activation using surface electromyography (EMG) during threshold loaded breathing with intensity of 30% and 50% maximal inspiratory pressure (PImax). Methods: This was a cross-sectional study. Patients with COPD diagnosis and a PImax lower than 60 cmH2O were recruited for the study. Surface EMG was used to measure the activation and the median frequency of diaphragm and SCM during quiet breathing, 30% and 50% PImax of threshold loaded breathing, and the first five minutes of recovery. Group-based trajectory modeling (GBTM) was used to identify diaphragm activation pattern across different breathing conditions. Generalized estimating equation (GEE) was then used to detect within and between differences of parameters among trajectory groups. Multiple regression analysis was used to identify factors associated with diaphragm and SCM activation. Significance p value was set at 0.05. Results: A total of 30 patients (25 males, 5 females) with COPD and a mean PImax of 46.7 (±13.3) cmH2O participated in this study. All patients demonstrated significant increases in diaphragm and SCM activation during 30% and 50% PImax of threshold loaded breathing compared to those of during quiet breathing (all p < 0.001), and the median frequency of diaphragm and SCM significantly decreased after both intensities of threshold loaded breathing (all p < 0.05). GBTM analysis identified two distinct patterns of diaphragm activation in response to threshold loaded breathing: low activation (n= 8) and high activation group (n= 22). Compared to high activation group, diaphragm activation and median frequency during quiet breathing and threshold loaded breathing were significantly lower in the low activation group (p < 0.05). Multiple regression analysis showed that the z-score of forced expiratory volume in one second to forced vital capacity ratio (FEV1/FVC z-score), diaphragm activation and median frequency during quiet breathing were associated with diaphragm activation during threshold loaded breathing, and only disease severity (z-score of forced expiratory volume in one second, FEV1 z-score) was associated with SCM activation during threshold loaded breathing. Conclusions: Diaphragm and SCM were activated to a greater extent in response to threshold loaded breathing in patients with COPD who had inspiratory muscle weakness. Diaphragm and SCM were fatigued after threshold loaded breathing. Furthermore, level of inspiratory muscle activation in response to threshold loaded breathing depended on their resting status. It is of clinical importance to find an optimal training strategy that would provide more benefit than harm when offering IMT for patients with COPD who have inspiratory muscle weakness.