Assessment of cough in dysphagia - added value or fancy fad?

Cough is a forced expulsive manoeuvre, usually against a closed glottis and with a characteristic sound. Voluntary and reflex cough are distinguished. Some authors describe the laryngeal expiratory reflex, a more immediate expulsive reflex without complete inspiratory phase. The neurophysiology of cough is complex and involves vagus nerve afferents, brainstem and cortical neural circuits, and phrenic, spinal motor and recurrent laryngeal nerve efferents to the diaphragm, intercostal, abdominal and laryngeal muscles. From a clinical perspective, cough may present a positive sign of respiratory disease; it may serve as a mechanism for clearing excess respiratory secretions; or it may serve as a defense against aspiration threat. Objective assessments of cough include reflex cough sensitivity testing, measurement of cough frequency, assessment of psychosocial aspects of cough (e.g. cough-related quality of life), and measurement of cough intensity (e.g. peak cough flow measurement). Current cough research is largely driven by the search for anti-tussive agents, but cough in the context of dysphagia has attracted increasing attention in recent years. Here, several aspects may be of interest. Unexplained coughing has long been interpreted as a potential red flag for undiagnosed dysphagia. More recently, the idea that cough impairment may correlate with presence and severity of dysphagia has inspired research. Could cough assessments at the bedside provide a convenient, non-invasive alternative to instrumental swallowing assessment for detecting silent aspiration? A slightly different line of reasoning explores cough assessment as an adjunct to clinical assessment of swallow. Could this added piece of information enhance clinical reasoning and management of dysphagic patients? The evidence base is growing, although clinical utility remains to be established. Variations in cough assessment methods complicate interpretation of the evidence base. Consensus on test standardisation (for example for reflex cough test or for peak cough flow measurement) will become important, if the intention is to establish absolute threshold values to guide clinical practice.