Bracing arms increases the capacity for sustained hyperpnea.

Patients with severe chronic obstructive pulmonary disease (COPD) frequently lean forward, bracing their arms. We wondered whether the resulting shoulder girdle support improves the function of the ventilatory pump. We tested this possibility in 4 normal men by measuring the maximal ventilation that they could voluntarily sustain for 4 min while seated with their elbows braced firmly on a table and while seated with their elbows held just above the table. Bracing the arms increased ventilatory capacity significantly in all subjects, but the magnitude of the change was small (8%). We attribute the change to improved function of the accessory muscles that expand the rib cage. We speculate that this effect assumes greater importance in patients with COPD, whose diaphragms are flattened and ineffective, because such patients depend more on the inspiratory muscles of the rib cage.