Assessment of Dysphagia Post ABI using Stroke Models of Care

Following a head injury a thorough assessment of swallowing is often required. Assessments may include a bedside clinical evaluation and/or a radiological procedure such as the MBS/VFSS or a Fiberoptic endoscopic examination of swallowing (FEES). Assessments should be completed throughout admission to a rehabilitation program. Deficits or any risk factors for swallowing difficulties must be taken into account when making dietary decisions. 

Although ERABI focuses primarily on intervention studies, information pertaining to assessment tools used in dysphagia practice have been included within this section since the authors felt it was clinically relevant. Although many of these tools are used in practice with ABI populations, none have been studied extensively within this population.

The Bedside Clinical Examination

Several forms of clinical or bedside swallowing evaluations have been described for the purposes of screening and/or assessment. Some of these methods target specific functions or tasks, while others evaluate swallowing ability using a more comprehensive approach. The clinical bedside examination typically involves general observations, an oral motor examination, a review of receptive and expressive language and ability to understand direction, and a review of current medications (Halper et al. 1999). The protocol may or may not include a water-swallowing test, and in some cases various consistencies of food and liquids. While bedside assessment is non-invasive and easy to perform, this method has been shown to poorly predict the presence of silent aspiration. Moreover, aspiration cannot be distinguished from laryngeal penetration using a bedside evaluation, resulting in the over diagnosis of aspiration and, in some cases, needless dietary restrictions (Smith et al. 2000).

The bedside clinical examination is generally completed by a Speech Language Pathologist (SLP) or a professional trained in dysphagia. This examination is generally completed once the patient’s history has been reviewed by the clinician (Logemann 1989). Clinicians are expected to make several observations: status of lip closure; oral versus nasal breathing; level of secretions; patient awareness of secretions; patient awareness of clinician’s approach; and the nature of content of initial verbalization by the patient (Logemann 1989).

Table: Aspects Included in Various Bedside Screening/Assessment Tools for Dysphagia

Author/Year

Components of Selected Dysphagia Screening/Assessment Tools

Westergren et al., (2001)
(Screening for eating difficulties)

  • Ingestion: sitting position, manipulation of food on plate, transport of food to mouth
  • Deglutition: opening or closing of mouth, manipulating food in the mouth

Perry
(2001)
(Screening)

  • Conscious level
  • Trunk control while seated
  • Volitional cough present
  • Control of saliva
  • Tongue control
  • Ease of breathing
  • Voice quality
  • Includes water-swallowing test

Mann et al.,
(2000)
(Assessment)

 

  • General examination: Consciousness, cooperation, language function, verbal/oral praxis, articulation
  • Oral preparation: Control of saliva, lip seal, tongue movement/strength, oral preparation, assessment of respiration
  • Oral phase: Gag reflex, palatal movement, oral transit time, bolus clearance , water swallowing test
  • Pharyngeal phase: Pharyngeal control/pooling, laryngeal elevation, reflex/voluntary cough, voice quality

Daniels et al.
(1997)
(Screening)

  • Assessment of mandible, lips, tongue, velum
  • Gag Reflex
  • Cough or voice change with swallow
  • Facial numbness/tingling
  • Dysphonia
  • Dysarthria
  • Volitional cough
  • Includes water-swallowing test

Smithard et al., (1996)
(Screening)

  • Conscious level
  • Head and trunk control
  • Breathing pattern
  • Lip closure
  • Palate movement
  • Laryngeal function
  • Gag
  • Voluntary cough
  • Includes water-swallow test

DePippo et al.,
(1992)
(The Burke Dysphagia Screening test)

  • Bilateral/brainstem stroke
  • History of pneumonia
  • Cough with feeding/3 oz. water
  • Failure to finish ½ of meals
  • Prolonged time required for feeding
  • Presently fed non-orally

Water Swallowing Test

The water-swallowing test originally required a patient to swallow 3oz (90ml) of water; however, smaller amounts have also been used. Although the water-swallowing test has not been studied in ABI, it warrants inclusion. This sensitivity and specificity of this test have been studied extensively within the stroke population and included in the table below.

Table: Sensitivity and Specificity of the Water-Swallowing Test (WST)

Discussion

To be clinically useful, screening tests need to be valid, reliable, easy to use, non-invasive, quick to administer (15-20 min) and pose little risk to the patient. Although many screening tools have been developed it is unclear how many of them are used in institutions beyond those where they were developed. Many institutions use informal processes, or simply restrict all food and drink until complete assessment by an SLP.

The results of a systematic review by Martino et al. (2000) evaluating the screening accuracy of 49 individual clinical screening tests for orophayngeal dysphagia suggested that there was only sufficient evidence to support the value of two tests: abnormal pharyngeal sensation and the 50 mL water-swallowing test. Both of these tests assessed only for the presence or absence of aspiration. Their associated likelihood ratios were 5.7 (95% CI 2.5-12.9) and 2.5 (95% CI 1.7-3.7), respectively. Limited evidence for screening benefit suggested a reduction in pneumonia, length of hospital stay, and personnel costs. More recently, Daniels et al. (2012) reviewed the sensitivity, specificity and positive likelihood ratio of items on 17 screening tools designed to detect aspiration. Items with high sensitivity (>80%) included weak palatal movement, cough on a 50mL and repeated 5 mL water swallowing test, dysarthria, abnormal volitional cough, abnormal voice and abnormal pharyngeal sensation. Only 1 item (impaired pharyngeal response) was associated with a likelihood ratio greater than 10, the clinically relevant threshold.

Videofluoroscopic Modified Barium Swallow Studies

When aspiration is suspected, the Videofluoroscopic Modified Barium Swallow Studies (VMBS) study is considered by some to be the “gold standard” in confirming the diagnosis (Splaingard et al. 1988). A VMBS study examines the oral and pharyngeal phases of swallowing; however, the patient must have sufficient cognitive and physical skills to undergo testing (Bach et al. 1989). The subject is placed in the sitting position in a chair designed to simulate the ideal/optimal mealtime posture. Radio-opaque materials of various consistencies are tested: barium impregnated thin and thick liquids, pudding, bread and cookies are routinely used. Various aspects of oral, laryngeal and pharyngeal involvement are noted during the radiographic examination. In some cases, the VMBS study can then be followed by a chest x-ray to document any barium, which may have been aspirated into the tracheobronchial tree. If a VMBS study is indicated and the result is positive, a second VMBS study may be appropriate in 1 to 3 months, if swallowing concerns persist.

Those patients who aspirate over 10% of the test bolus or who have severe oral and/or pharyngeal motility problems on VMBS testing are considered at high risk for pneumonia (Logemann 1983; Milazzo et al. 1989). In many cases, it is difficult to practically assess whether 10% or more of the test bolus has been aspirated, particularly since images are seen two dimensionally. Nevertheless, the degree of aspiration seen on VMBS study is a critical determinant of patient management. Predicting whether a patient will develop pneumonia post aspiration is, to some extent, dependent on other factors such as the immune state or general health of the patient with ABI.

The VMBS assessment not only establishes the presence and extent of aspiration but may also reveal the mechanism of the swallowing disorder. Aspiration most often results from a functional disturbance in the pharyngeal phase of swallowing related to reduced laryngeal closure or pharyngeal paresis. A VMBS study is recommended in those cases where the patient is experiencing obvious problems maintaining adequate hydration/nutrition, where concern is expressed regarding frequent choking while eating, or in the case of recurrent respiratory infections. Other factors such as cognition, depression, underlying lung disease, and being immunocompromised must also be considered.

Table: Radiological Evaluation during VMBS (Bach et al. 1989)

Oral Phase

Lips

Closure

Tongue

Anterior and posterior motion with consonants; motion and coordination during transport, and manipulation of the bolus

Soft Palate

Evaluation and retraction with consonants

Jaw

Motion

Oral

Pocketing

Pharyngeal Phase

Swallow

Delay, absence

Peristalsis or pharyngeal stripping

Residue in valleculae, pyriform sinuses, nasopharnyngeal regurgitation

Laryngeal Phase

Elevation of larynx

Penetration into laryngeal vestibule

Aspiration

Cough

Presence, delay, effectiveness/productiveness

Vocal cord function

Post Exam Chest X-Ray

Chronic Stages

Presence of barium in valleculae, pyriform sinuses, tracheobronchial tree, lungs

 

 

Videofluoroscopic Modified Barium Swallow (or Modified Barium Swallow) studies may be used as a tool to assist in dysphagia management and identification of aspiration in the ABI population.

 

Fiberoptic Endoscopic Evaluation of Swallowing

Although VMBS (or MBS) studies are considered by some to be the gold standard for detection of aspiration, other clinical assessment techniques are currently used as they are designed to be less invasive, more cost effective, and easier to administer. FEES, also referred to as flexible endoscopic evaluation of swallowing, is recognized as an objective tool for the assessment of swallowing function and aspiration. FEES is a procedure that allows for the direct viewing of swallowing function by passing a very thin flexible fiberoptic camera through the nose to obtain a view directly down the throat during swallowing. FEES allows for the full evaluation of the swallow function as food passes from the mouth into the throat. The evaluation identifies functional abnormalities and helps to determine the safest food texture and position for the patient in order to maximize nutritional status and eliminate the risk of aspiration and unsafe swallowing.

In addition to assessing the motor components of swallowing, FEES can also include a sensory testing assessment when an air pulse is delivered to the mucosa innervated by the superior laryngeal nerve. This form of assessment is known as flexible endoscopic examination of swallowing with sensory testing.

Table: Studies Evaluating FEES for Stroke Patients

Discussion

Aviv (2000) compared the incidence of pneumonia over a one-year period between patients managed by MBS or FEES with sensory testing. Among the stroke patients, the incidence of pneumonia managed by FEES with sensory testing was significantly lower. The authors speculated that one of the reasons for the lower incidence might be due to the sensory testing component of the FEES examination, absent from the MBS evaluation, which was used to more effectively guide management.

Rather than attempt to compare the accuracy of swallowing abnormalities assessed between VMBS and FEES evaluations, Leder and Espinosa (2002) compared the ability of six clinical identifiers of aspiration (dysphonia, dysarthria, abnormal gag reflex, abnormal volitional cough, cough after swallow, and voice change after swallow), with FEES to determine the accuracy of predicting aspiration risk following stroke. Their results suggest that the ability of the test to correctly identify patients not at risk of aspiration was poor using clinical criteria. Two studies suggest FEES as the gold standard to assess the accuracy of either the water-swallowing test and/or pulse oximetry to detect aspiration within the stroke population (Chong et al. 2003; Lim et al. 2001).

 

Although FEES may be less invasive and less costly to complete, further investigation would be beneficial to determine its effectiveness in identifying swallowing difficulties or aspiration post stroke. To determine its effectiveness within the ABI/TBI population, more research needs to be done.

 

Pulse Oximetry

Pulse oximetry has also been suggested as an alternative to detecting aspiration, based on the principle that aspiration of food into the airway leads to bronchospasm or airway obstruction, which leads to a reduction in oxygen saturation. This technique is non-invasive, requires little patient cooperation and is easy to obtain; however, its accuracy in detecting aspiration is unproven and it remains uncertain whether oxygen desaturation can predict aspiration. Wang, Chang, Chen, and Hsiao (2005) reported no significant association between the reduction in oxygen saturation and aspiration, identified simultaneously by VMBS, among 60 patients with dysphagia due to stroke and nasopharyngeal cancer, while Collins and Bakheit (1997) reported that pulse oximetry could be used to detect a high proportion of stroke patients who aspirated on the VMBS study.

Table: Studies Evaluating Pulse Oximetry in Stroke Patients

Although pulse oximetry is a quick and non-invasive method to detect aspiration following stroke, its association with oxygen desaturation has been inconclusive. Generally, its performance when measured against VMBS studies has been poor as the low sensitivities/specificities from the above studies will attest to.

 

There is limited evidence supporting the use of pulse oximetry alone to detect aspiration in patients who have had a stroke.

 

Pulse oximetry does not appear to be as sensitive a test as VMBS in determining aspiration post stroke.  Research needs to be completed within an ABI population.

 

Blue Dye Assessment for Swallowing

The blue dye assessment for swallowing has been used since the early ‘70’s with patients who have a tracheotomy; however, the accuracy of the test has been questioned since the 1980’s (O'Neil-Pirozzi et al. 2003). For patients with a tracheostomy, this assessment involves placing blue dye on the tongue or, in the case of the modified blue dye test, mixing it with water or semisolid food.  If blue dye appears in or around the tracheostomy tube, or at defined intervals during suctioning, then the patient has possibly aspirated. This test tends to be relatively easy to administer, inexpensive and can be performed at a patient’s bedside. Unfortunately research has shown the test may have a 50% false-negative error rate in the detection of aspirated material (Belafsky et al. 2003; Brady et al. 1999; Donzelli et al. 2001). Belafsky et al. (2003) in a study of 30 patients with tracheostomies conclude that the use of the Modified Evans Blue Dye (MEBD) test is beneficial with patients who have a tracheostomy tube (82% sensitivity) and in particular those who receive mechanical ventilation (100% sensitivity). O'Neil-Pirozzi, Momose, et al. (2003) found the blue dye test was unable to correctly identify aspiration in 20% of study’s tracheostomy patients and 38% of tracheostomy patients who were not aspirating.

Brady et al. (1999) in a study looking at the effectiveness of the MEBD test and theVMBS found the MEBD test was not able to detect “trace amounts” of aspiration in patients who had a tracheostomy.  On the other hand, if patients aspirated more than “trace amounts”, then the MEBD was able to detect it.  Brady et al. (1999) recommended that MEBD be followed by a VMBS to rule out the possibility of trace aspiration. Although this test is used in practice with individuals post ABI, no studies were found looking at its effectiveness within that specific population.

 

Modified Evans Blue Dye Test may be beneficial if patients aspirate more than trace amounts.

 

Caution is recommended when using the MEBD test alone to ascertain aspiration in individuals who have a tracheostomy.

 

Other Methods Using Stroke as a Model of Care

In addition to conventional assessment methods, tracheal pH monitoring has been used experimentally to detect drops in pH, which may indicate aspiration. Clayton et al. (2006) reported that in 9 of 32 patients examined, there was a drop in tracheal pH following ingestion of acidic foods. Tracheal pH was monitored by the use of a sensor, which was inserted into the trachea by the cricothyroid membrane. All patients were studied following the ingestion of foods which had been considered to be safe on the basis of a VMBS examination.

Other forms of clinical assessment have been used to detect the presence of aspiration. Ryu, Park, and Choi (2004) evaluated voice analysis as a means to clinically predict laryngeal penetration among 93 patients (46% of whom had suffered a stroke) using VMBS as the diagnostic gold standard.  Of five voice parameters tested (average fundamental frequency, relative average perturbation, shimmer percentage, noise-to-harmonic ratio, and voice turbulence index), relative average perturbation most accurately predicted aspiration.

Cervical Auscultation

Cervical auscultation is generally conducted using a stethoscope or some other listening device (Borr et al. 2007; Leslie et al. 2007; Youmans & Stierwalt 2005). It is believed that this type of test can provide additional information on the pharyngeal swallow in all patients without any additional costs or by using any intrusive methods (Borr et al. 2007; Youmans & Stierwalt 2005).

Cervical auscultation was compared to the VMBS in patients being treated for dysphagia (Zenner et al. 1995). Although agreement was found between the two tests on the oral phase, pharyngeal phase and diet management components, the VMBS did appear to be slightly more sensitive in identifying patients who had aspirated. In another study, Stroud, Lawrie, and Wiles (2002) found that raters were able to identify patients who were aspirating quite easily but challenges arose when evaluating patients who were not aspirating resulting in a significant number of false positives. Due to the limited evidence for cervical auscultation, caution should be taken when using this technique (Leslie et al. 2007). Again, research is needed in this area for individuals who were diagnosed with dysphagia post ABI specifically.