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 which 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 describes a respiratory rate greater than normal (which varies with age in childhood and is 14-18 breaths per minute in an adult).
Hyperpnoea describes a greater than normal level of ventilation (minute ventilation) which may be normal to meet metabolic requirements (eg. 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.
(ii) Pathophysiology
The pathophysiology of dyspnoea is poorly understood. Normal breathing is controlled by respiratory centres in the brain stem. The vagus nerve carries efferent and afferent components and provides the pathway for the neurological input resulting in the sensation of dyspnoea. Intrapulmonary parenchymal stretch receptors, carotid body and central medullary chemoreceptors, peripheral vascular receptors and pulmonary artery baroreceptors all contribute to the pathways leading to dyspnoea. Input from these receptors is integrated in the cortical and subcortical respiratory centres.
Chemoreceptors:
Hypercapnia is well recognised as a cause of dyspnoea; however the relationship between hypercapnia and dyspnoea is not straightforward patients with
3. Dyspnea is used to
describe an unpleasant
awareness of increased
respiratory effort.
Dyspnea is a common
presenting complaint to
the Emergency
Department
9. Investigation(Generic investigation)
Pulse oximetry
• simple, accurate, non-invasive and
continuous means of monitoring
arterial oxygen saturation
• Determine degree of hypoxia
Determine need for, and response
to, oxygen supplementation
ABG
• acid/base status
• O2 / CO2 status
• metabolic or respiratory /
acidosis or alkalosis
• A-a gradient
