Elastic and resistive loading in chronic obstructive lung disease.

R espiratory neuromuscular output as measured by the mouth occlusion pressure increases in normal subjects when the resistance to airflow is heightened acutely. In studies conducted by Altose et al’ in patients with chronic obstructive lung disease, the compensatory response to resistive loading was found to be significantly blunted. The diminished occlusion pressure response to flow loading in patients with chronic obstructive lung disease could be due to inspiratory muscle weakness or muscle fatigue. Alternatively, abnormalities in the function of proprioceptive receptors in the muscles of the thoracic cage or in vagal mechanoreceptors in the lung or their central processing could explain the abnormal response to external flow loading. It was reasoned that defective respiratory muscle function should affect the occlusion pressure response to both types of loads equally. If impairment of sensory mechanisms accounted for the blunted P,00 response to flow loads in COPD the response to an elastic load need not be affected. To further evaluate these possibilities, we compared the effects of elastic and inspiratory flow resistive loads on ventilation and occlusion pressure in patients with COPD.