DYSPNEA

  • 1 January 1979
    • journal article
    • research article
    • Vol. 15  (5) , 789-804
Abstract
Dyspnea is the medical term for the patient''s or subject''s complaint of shortness of breath. It encompasses the respiratory discomfort experienced in many different disease states and the shortness of breath felt by a normal subject during or after strenuous exercise. Several parameters which have been shown to correlate with the onset or severity of dyspnea are described, including: reduced vital capacity, the ratio of minute ventilation to vital capacity, reduced breathing reserve, the work of breathing and the O2 cost of breathing. Attempts at quantitation of dyspnea usually consisted of measuring physiological parameters associated with the sensation, such as the dyspneic index. The direct measurement of respiratory sensations using modern psycho-physical methods is at an early stage of development. Since the observation that the existence of dyspnea is often unrelated to any disturbance of arterial blood gas composition, it has been generally held that the mechanism of dyspnea is primarily neurophysiological. The neural pathways may conceptually be divided into those which transmit the dyspnea message from the respiratory apparatus to integrating centers in the brain and those concerned with subsequently bringing the sensation of the level of consciousness. Apparently there is no single sensing mechanism and neural pathway able to explain dyspnea in the diverse population of patients and subjects who experience unpleasant respiratory sensations. Three theories concerning mechanisms of dyspnea are described as follows: length-tension inappropriateness, vagal afferent activity especially from the J receptors and the recent concept of diaphragmatic fatigue. Some specific characteristics of the shortness of breath experienced in certain disease states are described, including chronic bronchitis and emphysema, bronchial asthma, pulmonary fibrosis and congestive heart disease.