An experimental study of the effect of stenosis upon the respiratory changes induced by muscular exercise

Dyspnea from muscular exercise results when the increased respiratory demands can no longer be met without effort. In the present series of experiments the ability to meet these demands was artificially restricted by having a normal individual (A. W. H.) breathe through small apertures. For this purpose two perforated corks were used, the diameters of the bores being 8 mm. and 6 mm. respectively. The first of these caused no effort so long as the subject of the experiments was at rest. It caused moderate respiratory effort when stairs were climbed at the rate of approximately 80 per minute. The second caused slight effort at rest and considerable distress during stair climbing. The latter culminated in discontinuance of the exercise after two or three minutes.During rest, the respiratory rate was not influenced by the milder obstruction but in some experiments was somewhat slowed by the more marked obstruction. During exercise, the respiratory rate was definitely slowed by each, average figures being: wit...