The mechanisms of dyspnoea

The mechanisms contributing to dyspnoea must be approached in an integrative manner. Sensations experienced in the act of breathing arise from the stimulation of multiple different receptors yielding different qualities of sensation. Different clinical conditions (cardiac, pulmonary and neuromuscular disorders) result in the overstimulation of many of these receptors. The patterns of stimulation may be unique, leading to different qualities of the discomfort experienced. Dyspnoea intensifies during exercise in virtually all patients regardless of the specific disorder. Exercise provides a stimulus contributing to dyspnoea, which can be applied across all disease states. Dyspnoea is closely related to the ventilation achieved, the capacity to breathe, and the strength of the inspiratory muscles across all clinical conditions. During exercise, patients will continue to exercise until the intensity of dyspnoea or leg fatigue (disproportionate increase in effort relative to the work performed) becomes intolerable. The symmetry between the intensity of dyspnoea and leg effort during exercise suggests that the mechanisms leading to exercise limitation are related to the activation of the muscles, Exercise testing is essential to the understanding of exertional dyspnoea in an integrated way.