Risk Factors for Dysphagia
The etiology of dysphagia in relation to acute cervical spinal cord injury is not completely understood. In addition to damaged nerves, the Consortium for Spinal Cord Medicine’s clinical practice guidelines on respiratory management following SCI (2005) has identified the following risk factors for dysphagia: supine position, spinal shock, slowing of gastrointestinal tract, gastric reflux, inability to turn the head to spit out regurgitated material, nausea inducing medications, recent anterior cervical spine surgery, presence of a tracheostomy, and age. Proper identification of risk factors in individuals at risk of dysphagia, can allow for early dietary intervention that could prevent secondary complications.
Discussion
Several risk factors have been associated with dysphagia incidence in individuals with SCI. Risk factors commonly identified were presence of a tracheostomy, ventilator use, age, nasogastric tube use, level of cervical injury, and presence of pneumonia.
Tracheostomies appear to be the most common factor for dysphagia. Tracheostomy tubes are used in individuals with SCI to facilitate ventilation and impaired cough reflexes (Shem et al. 2011). Prolonged use of tracheostomy tubes reduces respiratory volume and subglottic pressure inadvertently increasing the risk of aspiration (Hayashi et al. 2017). Aspiration can also occur due to leakage of secretions around the cuff depending on how well the tracheostomy tube is sealed (Chaw et al. 2012). The utilisation of a tracheostomy tube may have a disruptive presence on motor and sensory functioning with aspiration potentially caused by glottis injury, loss of protective reflexes, fixation of the trachea to the anterior neck skin, and esophageal obstruction due to the cuff’s contact with the esophagus and hypopharynx (Kirshblum et al. 1999). Shem et al. (2011) also point out that the poor secretion is a risk factor for both pneumonia and dysphagia and this is managed with tracheostomy tubes; therefore, the connection between dysphagia and tracheostomy tubes may be better explained through management of secretion difficulties.
Ventilator use was also a frequent risk factor for dysphagia. There exists a multitude of ventilation techniques all with goal of assisting in respiration and secretion management to simulate coughing (Wong et al. 2012). Chaw et al. (2012) explain that confirming a causal relationship between dysphagia and ventilator dependence and/or tracheostomy is difficult due to the latter’s link with pneumonia and as such, patients may require greater intensive intervention in order to improve their health. This assertion is supported by Wong et al. (2012) who stated that with aspiration and pneumonia being major complications of dysphagia, the need for ventilator support increases. This in turn complicates directionality as to the definitive cause of dysphagia with ventilator support and pneumonia acting as both independent and interrelated risk factors.
Age has been identified as risk factor for many diseases and conditions. Age is believed to increase the risk of dysphagia because increasing age is associated with changes in the physiology of the upper esophageal sphincter and pharyngeal region, blunting individuals’ sensation and motility during the swallowing reflex (Hayashi et al. 2017).
Nasogastric tubes are used for acute SCI for gastrointestinal decompression. The nasogastric tubes impede swallowing as it traditionally passes through the lumen of the pharynx. Nasogastric tubes can consequently lead to aspiration as they: lower the anatomical integrity of the upper and lower esophageal sphincters, increase the frequency of transient lower esophageal sphincter relaxations, and lead to a desensitization of the pharyngoglottal adduction reflex (Chaw et al. 2012).
The consortium guidelines should be updated to reflect these more commonly identified risk factors present in the literature.
Conclusion
There is level 5 evidence (from several observational studies: Hayashi et al. 2017, Chaw et al. 2012, Shem et al. 2012, Shem et al. 2012b, Shem et al. 2011, Shin et al. 2011, Seidl et al. 2010, Shem et al. 2004, Abel, Ruf & Spahn 2004, Brady et al. 2004, Kirshblum et al. 1999) that presence of a tracheostomy is a risk factor for dysphagia in individuals with SCI.
There is level 5 evidence (from six observational studies: Chaw et al. 2012, Shem et al. 2012, Shem et al. 2012b, Shem et al. 2011, Seidl et al. 2010, Shem et al. 2004) that ventilator use is a risk factor for dysphagia in individuals with SCI.
There is level 5 evidence (from six observational studies: Hayashi et al. 2017, Shem et al. 2012, Shem et al. 2012b, Shem et al. 2011, Shin et al. 2011, Kirshblum et al. 1999) that increasing age is a risk factor for dysphagia in individuals with SCI.
There is level 5 evidence (from four observational studies: Chaw et al. 2012, Shem et al. 2012, Shem et al. 2012b, Shem et al. 2011) that presence of nasogastric tubes are a risk factor for dysphagia in individuals with SCI.
