Does the diaphragm contribute to balance control in patients with COPD?

Abstract

<b>Background:</b> Patients with COPD, particularly those with low diaphragmatic strength, show balance deficits. <b>Aim:</b> To observe diaphragm activity during balance control in patients with COPD, and its association with postural sway. <b>Methods:</b> Patients with COPD (n=11, 66±6 years old, FEV1/FVC 57±16%, inspiratory muscle strength 89±17% predicted) performed ballistic arm movements in upright standing during different combinations of support surface (stable/foam), vision (yes/no), arm movement direction (anteflexion/abduction), frequency (single/repetitive), and breathing mode (normal/breath holding at end-expiration). Postural sway was measured as center of pressure (COP) displacement, and diaphragm activity was measured as electromyography (EMG) amplitude using an esophageal catheter. Outcomes were change in COP displacement and EMG amplitude between baseline and the arm movement phase, and the correlation between. <b>Results:</b> Adding single or repetitive arm movements to upright standing significantly increased (1) postural sway, in anteroposterior and mediolateral direction (p&lt; 0.05), and (2) diaphragm EMG amplitude (p&lt; 0.05). This latter was independent from support surface and vision condition (p&gt; 0.05). These increased diaphragm EMG amplitudes during arm movements were moderately to strongly associated with corresponding increases in postural sway, even during end-expiratory breath holding, which excludes inspiratory diaphragm activity (0.50&lt; ϱ &lt; 0.75, p&lt; 0.05). <b>Conclusion:</b> Challenging balance in patients with COPD increases diaphragm activity, which correlates with postural sway disturbance and irrespective of breathing. This confirms the existence of a postural role of the diaphragm in patients with COPD.