Neck muscle activity in patients with severe chronic obstructive pulmonary disease

The present studies were designed to assess the pattern of activity and the frequency of activation of the neck muscles in patients with chronic obstructive pulmonary disease (COPD). Using concentric needle electrodes, we thus recorded the electromyograms of the scalene, sternocleidomastoid, and trapezius muscles during resting breathing in 40 stable patients with severe chronic airflow obstruction (FEV1 = 0.69 +/- 0.18 L) and hyperinflation (FRC = 228 +/- 40% of predicted); 17 patients were hypercapnic at rest. When breathing in the seated posture, all patients (100%) had strong inspiratory contraction of the scalenes. In contrast, no patient showed inspiratory activity in the trapezius, and only four patients (10%) showed definite, invariable inspiratory activity in the sternocleidomastoid. These two muscles were silent in the supine posture as well, even though the adoption of this posture was associated with an increase in dyspnea in most patients. We conclude, therefore, that in contrast to conventional thinking, most stable patients with severe COPD do not use the sternocleidomastoids or the trapezii when breathing at rest. Additional measurements indicated that the sternocleidomastoid inspiratory activity previously recorded in such patients was in general caused by a cross-contamination from surrounding muscles.