Context and Definition

‘Breathlessness’ or ‘shortness of breath’ is a common presenting complaint to the emergency department (ED). There are a large number of causes for this presentation and several medical terms used to describe it (see below) but no concise definition. It is described as a subjective feeling of difficult or uncomfortable breathing or a feeling of ‘not getting enough air’.

Various medical terms exist and are used to describe different aspects of breathlessness:

• Dyspnoea is an overall term used to describe an unpleasant awareness of increased respiratory effort and will be used synonymously with ‘breathlessness’ in this session
• Tachypnoea Tachypnoea describes a respiratory rate greater than the normal range. This varies with age during childhood, and 14-18 breaths per minute in adults
• Hyperpnoea describes a greater than normal level of ventilation (minute ventilation), which may be normal to meet metabolic requirements (e.g. during exercise)
• Hyperventilation describes a situation where over-breathing results in a lowering of alveolar and arteriolar PCO₂; in this situation, minute ventilation exceeds metabolic demand
• Orthopnoea describes breathlessness on lying flat. It is due to redistribution of blood leading to an increased central and pulmonary blood volume and to abdominal contents pressing against the diaphragm in the recumbent position
• Paroxysmal nocturnal dyspnoea describes a sudden onset of dyspnoea usually occurring at night and waking the patient from sleep; the mechanism is similar to orthopnoea but the sensory awareness of the developing situation is depressed by sleep
• Bradypnoea describes an inappropriately reduced respiratory rate which can occur when a patient becomes exhausted following prolonged tachypnoea or following ingestion of certain toxins
• Cheyne Stokes breathing is an abnormal breathing pattern characterised by progressively deeper and/or faster breathing, followed by a gradual decrease in depth/rate that results in temporary apnoea and is caused by damage to the respiratory centres in the brainstem

Learning Bite

Dyspnoea is an overall term used to describe an unpleasant awareness of increased respiratory effort and is used synonymously with ‘breathlessness’ in this session.