Shortness of Breath

Abstract

This paper reviews our knowledge of the nature and causes of breathlessness and discusses its assessment and investigation. The control of respiration by the respiratory centre involves a calculation of the ventilatory demand through nervous and chemical stimuli and knowledge of its achievement by the ventilatory effector mechanism. It remains unconscious unless the muscular effort required is disproportionate to the volume of ventilation achieved. Experimental work on the loading of respiration is described because of its bearing Os the mechanism of the sensation of breathlessness in pathological conditions of the lung. The clinical assessment of dyspnoea by history and physical examination is detailed with reference to the most useful diagnostic points. Physiological tests are required to distinguish between the two chief mechanical abnormalities of pulmonary function in chest disease. Obstructed ventilation, as in asthma or chronic bronchitis, is thus contrasted with the findings in restricted ventilation produced by fibrosis of the lung or deformity of the chest such as kyphoscoliosis. Measurements of the gases of the arterial blood are required for the detection of alveolar hypoventilation which follows extensive derangement of pulmonary function and involves the respiratory centre itself. In contrast to knowledge of the mechanism of dyspnoea in chest disease, that occurring in heart disease, anaemia, and pregnancy remains largely unexplained. The simple explanation that the compliance of the lung is reduced by pulmonary hypertension or pulmonary oedema in mitral stenosis or left heart failure is regarded as inadequate. Analogy is drawn between the hyperventilation of patients with heart disease or anaemia and that of normal subjects at the limit of exertion, when oxygen uptake increases less than the volume of ventilation. © 1964, British Medical Journal Publishing Group. All rights reserved.