Explanation
This module covers other screening tests for dysphagia that are frequently seen in books and the academic literature and are frequently performed in clinical practice. As with other assessment methods, we must be well acquainted with test techniques, interpretation and detection accuracy, safety, and potential adverse events and its management before actually using in clinical practice.
Explanation
In this module, we look at various types of water swallowing tests (besides the modified water swallowing test), cervical auscultation, the Evans blue dye test, and pulse oximetry.
Explanation
Water swallowing tests are the easiest to set up and we evaluate swallowing by having the patient drink water, a substance essential to sustaining life. For these reasons, water swallowing tests are often used as screening tests to determine whether patients are candidates for direct training. For use in testing, water is truly the only test food or drink that has universal properties: everyone drinks water regardless of their diet or preferences, and it can be given to anyone anywhere in the world under any circumstances. Water flows quickly and easily cause aspiration, but it causes fewer adverse events than other liquids and solids used in testing if the volume aspirated is small. Elderly adults and other patients with reduced laryngeal or tracheal sensitivity are prone to silent aspiration if they aspirate a small volume of water because their cough reflex is not stimulated. For this reason, it's best to combine this test with cervical auscultation (described later) in such patients. A test that uses a small volume of water should be selected for patients who, based on their condition, are thought to be at high risk of aspiration.
Explanation
In Japan, Kubota et al. published an article describing a 30-mL water swallowing test in 1982. In this test, examiners observe patients until they have finished swallowing the water and then grade the attempts on a 5-point scale. The examiners also record any episodes (eg, slurping or choking) that occur while drinking the water. However, the sensitivity and specificity of this test for detecting aspiration are unknown.
Explanation
Other variations of the water swallowing tests divide the overall volume of water given into stages, use thickened water, or use different volumes of water.
In one variation that uses a total of 30 mL of water, patients first drink two 5-mL spoonfuls of water one at a time and then swallow the remaining water if the initial swallows were normal. This test has sensitivity of 0.72 and specificity of 0.67 for detecting aspiration by choking and voice changes.
To date, water swallowing tests involving different volumes of water-including 10 mL, 50 mL, 3 oz (about 90 mL), 100 mL, and 150 mL-have been studied in and outside Japan. However, each study had different subjects (eg, elderly adults, patients with cerebrovascular disease, and patients with head and neck cancers) and also their determination criteria and accuracy varied.
In other words, currently there's no established gold-standard test like the modified water swallowing test that has water volume and determination criteria accepted by strong expert consensus. However, because the 3-mL volume of water used in the modified water swallowing test is unlikely to stimulate a swallowing reflex in many patients, the volume of water generally considered appropriate for a single swallow of water is 20-25 mL, and it's common when making house calls to encounter patients with a restricted diet who routinely drink half a cup of water or more, there is strong demand for a water swallowing test that uses a defined volume of about 100 mL and has determination criteria and accuracy that are accepted by expert consensus.
In the simple two-step swallowing provocation test (SPT), a 5-Fr catheter is inserted nasally into the upper part of the pharynx with the patient in the recumbent position, stimulation of the swallowing reflex with 0.4 mL of injected water is observed, and then swallowing of 2 mL of injected water is observed. The absence of a swallowing reflex in the 3 s after water injection is considered an abnormal finding. This test grades stimulation of the swallowing reflex, and it has been compared with the water swallowing test for detection of aspiration pneumonia. The 10-mL and 30-mL water swallowing tests, which use choking and wet hoarseness as the criteria for an abnormal result, have respective sensitivity of 0.71 and 0.72 and specificity of 0.71 and 0.70 for detection of aspiration pneumonia. In contrast, SPT has sensitivity of 1.00 and specificity of 0.84 with 0.4 mL of water and sensitivity of 0.76 and specificity of 1.00 with 2.0 mL of water. However, the relationship between the SPT results and actual aspiration during eating and drinking is unclear. It's necessary for us to understand that this test is not designed to screen for aspiration or laryngeal penetration during swallowing, but rather to detect patients who are at high risk of aspiration pneumonia. Also, some experts are opposed to the method itself and believe that it is not advisable to give an additional 2 mL of water to patients in the recumbent position whose swallowing reflex was not stimulated by 0.4 mL of water.
Explanation
Cervical auscultation is performed by listening to swallowing sounds and breath sounds using a stethoscope. The sensitivity and specificity of this method have been reported as 0.84 and 0.71 for general detection of aspiration and 0.66 and 0.62 for detection of aspiration with marked laryngeal penetration. The concordance rate with findings of videofluoroscopy was found to be 83% in a videofluoroscopic study when swallowing sounds and breath sounds before and after swallowing were evaluated by audio analysis for abnormalities such as aspiration, laryngeal penetration, and pharyngeal retention.
These sounds can be evaluated using either the diaphragm or the bell side of the stethoscope, but an infant stethoscope or other small stethoscope is easiest to use on the neck, and placement on the skin surface at the lateral border of the trachea directly below the cricoid cartilage is considered most appropriate to detect sounds produced during swallowing.
When a healthy person swallows, we can hear clear breath sounds followed by the sound of breath-holding as swallowing occurs, then swallowing sounds, and then clear expiratory sounds after swallowing. If there is some abnormality, we tend to hear sounds such as food being moved down the pharynx before the swallowing reflex is stimulated, wheezing, coughing (a non-breathy cough can clearly be heard by auscultation), clearing of the throat, and wet hoarseness.
Explanation
This shows abnormal swallowing and breath sounds.
Long, weak or multiple swallowing sounds suggest Propulsion disorder, weak pharyngeal contraction, laryngeal elevation disorder and/or insufficient opening of upper esophageal sphincter.
bubbling sound, coughing up sounds with choking are consistent with aspiration.
Respiratory sounds between swallowing sounds is related with Discoordination between breathing and swallowing, penetration and/or aspiration.
wet sound, gargling sound are suggestive of Pharyngeal residue, laryngeal penetration, aspiration.
coughing up sounds with choking, wheezing also suspect aspiration.
Explanation
Here is a summary of specific auscultation techniques. There are different cervical auscultation techniques for patients who can follow instructions and patients who can't. It is critical that we carefully confirm patients have clear breath sounds before swallowing and to compare those breath sounds with breath sounds after swallowing.
In either case, the test is repeated while changing conditions such as the food or drink given, the volume given, and posture. If you suspect aspiration after patients have swallowed the food or drink given, stop the test immediately and promptly remove the aspirated material by expulsion (by bending forward and huffing) or suctioning.
Explanation
These tests were devised as screening tests for aspiration in patients with a tracheostomy. Evans blue is a reagent injected into blood vessels to test for damaged cells and vascular permeability. It was probably used for these tests because the dye is believed not to have any major effects on the body even when administered endotracheally. Be aware that use of any other dye has not been established as safe.
In the original Evans blue dye test, droplets of 1% concentration Evans blue dye are applied to the tongue every 4 h, and blue exudate from the tracheostomy is considered to indicate aspiration. The modified Evans blue dye test uses dye mixed with a semisolid or liquid. Sensitivity and specificity are 0.80 and 0.62 for the original test and 0.82 and 0.38 for the modified test.
Explanation
Past studies have shown that a decrease in SpO2 after swallowing is associated with aspiration, but many disagree with that idea today. SpO2 would naturally not decrease with aspiration of a small amount of material in someone with normal cardiopulmonary function, which is why SpO2 cannot be used to screen for aspiration.
However, monitoring of SpO2 as an indicator of the patient's general condition is very important, and any decrease in SpO2 during direct training must be considered a sign of an event too important to ignore, such as aspiration of a large volume of material.
References
- Takahashi K (supervisor of translation): Dysphagia Clinical Management in Adults & Children (Japanese translation) Ishiyaku publisher, Tokyo 2011
- Saitoh E & Ueda K (Eds) : Dysphagia Rehabilitation 3rd edition. Ishiyaku publisher, Tokyo 2016
