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Lee C-T1, Hsu M-J2, Chien J-Y3, Wu H-D4, Wang L-Y1,5
1National Taiwan University, School and Graduate Institute of Physical Therapy, Taipei, Taiwan, 2Kaohsiung Medical University, Department of Physical Therapy, Kaohsiung, Taiwan, 3National Taiwan University Hospital, Department of Internal Medicine, Taipei, Taiwan, 4National Taiwan University Hospital, Department of Integrated Diagnostics and Therapeutics, Taipei, Taiwan, 5National Taiwan University Hospital, Physical Therapy Center, Taipei, Taiwan
Background: 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. The main target of IMT is to train diaphragm and improves its function. The accessory muscles would be recruited to assist ventilation with increasing ventilatory demand in healthy adults. Compared to healthy adults, ventilatory demand is already increased during quiet breathing (QB) in patients with COPD, and thus, we hypothesized compensatory recruitment of neck accessory muscles could be observed during inspiratory threshold loaded (ITL) tasks.
Purpose: To exam sternocleidomastoid (SCM) activation using surface electromyography (EMG) at 30% and 50% of maximal inspiratory pressure (PImax) ITL tasks in patients with COPD.
Methods: Patients with COPD were recruited for the study. Surface EMG was used to measure SCM activation during various breathing tasks (QB, maximal inspiratory, 30% PImax and 50% PImax). Root mean square (RMS) values from 10 breaths during different breathing tasks were calculated and normalized to RMS during maximal inspiratory task to represent the activation of SCM (% EMGSCM). Median frequency of SCM (MFSCM) was calculated to exam muscle fatigability. Generalized Estimating Equation was used to detect the differences of variables between various breathing tasks. Significance α level was set at 0.05.
Results: A total of 30 patients with COPD with inspiratory muscle weakness (PImax: 46.7±13.3 cmH2O) were included in this study. The mean (±SD) age of the patients was 71.2 (±8.2) years. % EMGSCM increased significantly during 30% PImax (62.4±20.5% ) and 50% PImax ITL tasks (74.5±19.0% ) compared to that of QB (11.7±9.7% ) (both p 0.001). Compared to QB (108.4±19.4 Hz), MFSCM decreased significantly during both ITL conditions (30% PImax: 67.9±12.6 Hz, and 50% PImax: 66.0±13.1 Hz; p 0.001).
Conclusion(s): Patients with COPD with weak inspiratory muscle would recruit SCM accessory muscle substantially during ITL tasks.
Implications: This study indicates that patients with COPD with weak inspiratory muscle might use compensatory breathing strategy during IMT, which might then compromise the expected training effect of IMT on diaphragm in this patient population.
Keywords: Chronic obstructive pulmonary disease, sternocleidomastoid, surface electromyography
Funding acknowledgements: No specific financial support was obtained for this study.
Purpose: To exam sternocleidomastoid (SCM) activation using surface electromyography (EMG) at 30% and 50% of maximal inspiratory pressure (PImax) ITL tasks in patients with COPD.
Methods: Patients with COPD were recruited for the study. Surface EMG was used to measure SCM activation during various breathing tasks (QB, maximal inspiratory, 30% PImax and 50% PImax). Root mean square (RMS) values from 10 breaths during different breathing tasks were calculated and normalized to RMS during maximal inspiratory task to represent the activation of SCM (% EMGSCM). Median frequency of SCM (MFSCM) was calculated to exam muscle fatigability. Generalized Estimating Equation was used to detect the differences of variables between various breathing tasks. Significance α level was set at 0.05.
Results: A total of 30 patients with COPD with inspiratory muscle weakness (PImax: 46.7±13.3 cmH2O) were included in this study. The mean (±SD) age of the patients was 71.2 (±8.2) years. % EMGSCM increased significantly during 30% PImax (62.4±20.5% ) and 50% PImax ITL tasks (74.5±19.0% ) compared to that of QB (11.7±9.7% ) (both p 0.001). Compared to QB (108.4±19.4 Hz), MFSCM decreased significantly during both ITL conditions (30% PImax: 67.9±12.6 Hz, and 50% PImax: 66.0±13.1 Hz; p 0.001).
Conclusion(s): Patients with COPD with weak inspiratory muscle would recruit SCM accessory muscle substantially during ITL tasks.
Implications: This study indicates that patients with COPD with weak inspiratory muscle might use compensatory breathing strategy during IMT, which might then compromise the expected training effect of IMT on diaphragm in this patient population.
Keywords: Chronic obstructive pulmonary disease, sternocleidomastoid, surface electromyography
Funding acknowledgements: No specific financial support was obtained for this study.
Topic: Cardiorespiratory
Ethics approval required: Yes
Institution: National Taiwan University Hospital
Ethics committee: Research Ethics Committee (REC) of National Taiwan University Hospital
Ethics number: 201802054RINB
All authors, affiliations and abstracts have been published as submitted.
