[Dyspnea and behavioral control].

Respiration is automatically regulated via chemo- and mechanoreceptors existing in and outside the lungs, but it is also controlled voluntarily by behavioral factors. Voluntary increase in ventilation accentuates dyspnea and the sensory intensity at a given ventilation does not differ from that of exercise-induced hyperventilation, but it is significantly smaller than that during hypercapnia or hypoxia. Voluntary constraint of ventilation augments dyspnea in proportion to the degree of constraint even under isocapnic hyperoxia, and the respiratory sensation during constrained breathing is qualitatively more discomfortable than that during hyperventilation. Changes in the level and pattern of breathing under constant levels of chemical stimuli increase respiratory sensations and the intensity of dyspnea is minimal near the spontaneous levels, which supports the hypothesis that breathing is behaviorally regulated in part to minimize dyspnea. The system of behavioral control of breathing appears to be involved in the maintenance of body homeostasis by modifying the respiratory output through respiratory sensations.