Dyspnoea and its measurement

Key points

• Dyspnoea is the sensation of breathing discomfort that can be described with different terms according to different pathophysiological mechanisms that vary in intensity.

• The mechanisms of dyspnoea are complex.

• In COPD, whilst the intensity and quality of dyspnoea during activity correlates with the magnitude of lung hyperinflation and inspiratory events, it correlates poorly with FEV₁.

• Valid, reliable and responsive instruments are available to measure the severity of dyspnoea in patients with respiratory disease.

CME article: educational aims

• To introduce dyspnoea and explain its mechanisms.

• To present dyspnoea descriptors, which may help in the understanding of the language of dyspnoea, and to relate these to specific diseases.

• To describe some of the methods available for the measurement of dyspnoea.

Summary Dyspnoea, a term used to characterise a subjective experience of breathing discomfort, is perhaps the most important symptom in cardiorespiratory disease. Receptors in the airways, lung parenchyma, respiratory muscles and chemoreceptors provide sensory feedback via vagal, phrenic and intercostal nerves to the spinal cord, medulla and higher centres. Knowledge of dyspnoea descriptors can help in understanding the language of dyspnoea and these are presented here. It is important to appreciate that differences in language, race, culture, sex and previous experience can all change the perception of and the manner in which the feeling of being dyspnoeic is expressed to others. Therefore, standard tools to measure dyspnoea are available. In addition, there are tools that can help to relate the severity of symptoms with observed levels of cardiac and pulmonary responses while performing supervised tasks. A range of methods are described here. Inventories that involve aspects of dyspnoea related to quality of life are not yet a routine part of the history and physical examination, although they have proved useful in the clinic. Measurement instruments may involve a cost for use, may be self-administered or require an interviewer, and can vary in the time required for completion and scoring.