Assessment of Swallowing Function in a Critically Ill Patient
In Question 14 from the second paper of 2008, the college asked the candidates to "list the possible causes of an altered swallowing reflex in a critically ill patient" and discuss some strategies for assessment thereof. Furthermore, Question 2 from the first paper of 2001 asks about the effects of a tracheostomy on swallowing.
A search of Oh's Manual for "swallowing", "reflex" and "altered" reveals no page where these words might be present in a useful combination. One must therefore turn to noncanonical resources. Of these, the best - Macht's 2014 article in Chest - is now available for free. Unfortunately it does not list the possible aetiologies, as the college asked. For that, one must turn to an ancient scroll from 1981. There, one finds an etching that reads "Fig. 2. Conditions that may predispose patients to swallowing dysfunction." Together with the author's own weird ideas, the content of that figure is incorporated into the list below.
Drug-induced swallowing dyfunction:
Idiopathic miscellaneous causes:
Endocrine and metabolic causes:
Assessment of swallowing in the ICU patient
Macht et al suggest several steps one should take to identify a patient as a poor swallower, and to assess the extent of their problem. With understandable abridgement, these are presented below.
Features which suggest that swallowing is impaired
- Fluctuating level of consciousness
- Assymetric lips
- Constantly open mouth
- Gurgling oral secretions
- A nasogastric tube
- Frequent suctioning of the oropharynx being required (more frequent than the suction of the ETT)
- Copious tracheal secretions
- A deviated uvula
- An absent gag reflex
One should complete an actual neurological examination before moving on with any formal assessment of swallowing. It would be embarrassing if the speech therapist made a diagnosis of MCA infarction before you did.
Bedside swallow evaluation: the "Sip Test"
The ancient physiotherapist reference contains a nice step-by-step guide to this simple bedside assessment:
- Get the patient sitting up, with the neck slightly flexed.
- Using a syringe, place 10 ml of water in the patient's mouth.
- Ask them to hold the fluid in the mouth.
- Then, ask them to swallow it.
- Swallowing dysfunction and aspiration are indicated by choking, coughing, or changes in breath sounds.
- If none of that happened, you can move on to test with a larger volume of water, or drinking with a straw.
This simple test - when using 3 American ounces of water (about 84ml) - predicts aspiration with a sensitivity of 96.5% and a specificity of 48.7% when compared to endoscopy as the gold standard. With a high false positive rate such as this, one will frequently end up "failing" otherwise normal patients, and moving on to more detailed methods of assesment.
The Speech Pathologist Evaluation
Realistically, this would be your next step. They go into the room, the curtains come down, something mysterious happens, and then in a few minutes the oracle emerges and brings forth a verdict.
What actually happens? An excellent article from Brazil outlines the typical speech pathologist assessment process:
- Preliminary Assessment Protocol: "an instrument that aims to describe overall aspects of breathing, speech, voice and of the orofacial and cervical structures of individuals undergoing a swallowing evaluation." Assessed domains include vital signs, alertness, tube feeding, orientation status, ability to follow single-step verbal commands, oxygen saturation, breathing pattern, dependence on oxygen, speech intelligibility, coordination between breathing and speaking, dysphonia, orofacial motor ability, dentition, gag reflex, cough quality, laryngeal elevation and saliva.
- Dysphagia Risk Evaluation Protocol: This is beautifully described by the Brazilian author as "the controlled offer of water and puree volumes". Performance during this test grades the patient's dysphagia as anywhere between Level I (normal swallowing) to Level VII (unable to even begin the swallow process).
- Oral Feeding Transition Protocol is something that happens if the patient performed reasonably well in the two other stages, and is ready to move on to some sort of diet. It takes into account the level of dysphaia, and uses published guidelines to recommend a diet of some sort - be it puree, with or without thickened fluids, or whatnot.
The outcome of a speech therapist assessment is therefore either a recommendation regarding the type of diet to feed this patient, or a recommendation regarding further investigations, which escalate in their invasiveness.
Nasendoscopy: Fiberoptic Endoscopic Evaluation of Swallowing (FEES)
This involves passing a 3.4-mm nasopharyngoscope through one nostril into the pharynx to view the glottis directly, with some preemptive anaesthetic/vasoconstrictor spray.
- With the endoscope watching, the contestant swallows food and liquids, and their performance is recorded for future review.
- Though this strategy may not actually affect one's management, it can predict aspiration.
- The direct observation of the vocal cords can also give important clues regarding the neurological cause of the swallowing dysfunction.
Videofluoroscopic Swallow Study (VFSS)
While a fluoroscopic Xray camera is watching, the patient is asked to swallow various foods and liquids. Their transit through the oropharynx and into the oesophagus is observed in real-time.
This is apparently the current gold standard of swallow evaluation. With food boluses of different viscosity, one is able to directly observe the effectiveness of intervention.
The influence of a tracheostomy on swallowing function
This has come up in Question 2 from the first paper of 2001, and has never appeared again. However, it has daily relevance in the pragmatic ICU sense.
A good paper from 1971 discusses this question in some detail.
In summary, the swallowing defects due to tracheostomy are as follows:
- It prevents the larynx from elevating normally
- thus, hypopharyngeal sphincter fails to open
- thus, food spills into the larynx
- It desensitises the sensation of the larynx, preventing normal cough in response to aspiration. The effect is likened to stroke-related bulbar dysfunction
- Long periods of being NG-fed result in the deconditioning of muscles involved in swallowing