**2. Dysphagia**

Swallowing is a complex sensoriomotor function that depends on the integrity of the mecha‐ noreceptors and chemoreceptors for the sequential stimulation and inhibition of the upper aerodigestive tract; this coordinated process transports foods and liquids through the mouth and pharynx to the esophagus [10] and simultaneously protect the upper airway [1].

Biomechanical events that contribute to secure bolus transport and airway protective mecha‐ nisms include: closure of the introitus to the trachea by vocal cord adduction, approximation of the adducted arytenoids to close the laryngeal aditus, epiglottal descent, antero-superior displacement of the larynx away from the path of the bolus, and opening of the upper oesophageal sphincter [11]. During swallowing, the closure of the larynx and the respiratory pause during swallowing are vital protective mechanisms that prevent aspiration [12]. This phenomena is describes schematically in Figure 2.

**Figure 2.** Simplified description of the usual swallowing pattern in healthy adults. Swallowing initiates during the ex‐ piratory phase of the breathing cycle. Swallowing interrupts exhalation (swallow apnea), and once the swallow has been completed, breathing resumes with exhalation.

Disordered swallowing, or dysphagia, can develop from lesions in certain areas of the cortex and brainstem that control the swallowing function, or damage to the associated cranial nerves. It is a common problem observed in patients with stroke and head injury [13]. Dysphagia affects at least 12% of patients in acute care hospitals and more than 50% of those in chronic care settings [14]. The presence of dysphagia is associated with aspiration induced chest infections and increases the risk of serious respiratory consequences such as pneumonia. Identification of the patient at risk of aspiration is important from a clinical view point. Due to the risk of aspiration, a significant number of dysphagic patients are fed with a nasogastric tube and /or intravenous fluids [13]. Dysphagia can significantly impact a person's quality of life as well as their health status [15].
