5.5 Assessment of Dysphagia Post ABI

Describe an Approach to the Assessment of Dysphagia Post ABI.

  1. Screening involves a bedside clinical evaluation to determine whether the patient has dysphagia or not.
     
  2. Assessment describes the dysphagia in detail, determines the severity of the problem, and guides a management approach.
     
  3. Patients are initially kept NPO.
     
  4. Clinical assessment is initially performed and if necessary a videofluroscopic modified barium swallow (VMBS) is done.

A thorough assessment of swallowing function involves both a bedside clinical evaluation plus a radiological procedure and will help to guide appropriate intervention strategies. The clinical bedside examination usually involves general observations, an oral motor examination, and a swallowing/feeding trial 6including the introduction of one or several teaspoons of water and in some protocols, various consistencies of food and liquids.  In one protocol, if patients were unable to successfully swallow a minimal amount of fluid, a small cup of water was carefully introduced.  The full assessment is described elsewhere 17.

Although many of the tools used in practice to assess swallowing disorders in those who have sustained an ABI, none of these tools have been studied extensively or specifically within this population.

Swallowing Recommendations 18

Persons with moderate to severe ABI should:

  • Be screened for risk of dysphagia and aspiration by an appropriately trained clinician
  • Be assessed by a speech language pathologist if there are features of dysphagia or aspiration to determine the appropriate feeding strategy. (ABIKUS A) (G69-p.27)

5.5.1 The Bedside Clinical Examination

Which bedside clinical examinations have been shown to be the most useful?

  1. Only two tests, the abnormal pharyngeal sensation and the 50 ml water-swallowing test have sufficient evidence supporting their use.

 

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. These methods may or may not include a water-swallowing test.  While bedside assessment is non-invasive and easy to perform, this method has been shown to predict poorly the presence of silent aspiration.  Smith et al. 19reported that 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.

The results of a recent systematic review by Martino et al. 20evaluating the screening accuracy of 49 individual clinical screening tests for oropharyngeal dysphagia suggest that there is 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 benefits suggested a reduction in pneumonia, length of hospital stay, personnel costs and patients.

5.5.2 Water Swallowing Test

The water-swallowing test although not specifically studied in ABI, warrants inclusion here. This test has however been studied extensively within the stroke population, to establish its validity as part of a clinical swallowing assessment. While the original test required a patient to swallow 3 oz (90ml) of water, smaller amounts have also been used.

When not provided, the positive predictive value (PPV), negative predictive value (NPV) and positive and negative likelihood ratios (+ LR & -LR) for the water-swallowing test were calculated for each study and summarized in the following table. The gold standard used to confirm aspiration was either VMBS or FEES examination. (We used the data provided by the authors from DePippo et al.21and found that the sensitivity and specificity reported were actually the PPV and NPV).  A likelihood ratio (LR) of either greater than 10 or less than 0.1 is considered to be strong evidence to either rule in or rule out disease (in this case, the presence of aspiration), while LRs less than 2 are considered to be small.

Table 2: The Positive and Negative Predictive Value and Positive and Negative Likelihood Ratios for the detection of Aspiration Using the Water Swallowing Test

Study

PPV (%)

NPV (%)

+ LR

- LR

DePippo et al.,21

59

76

1.75

0.37

Garon et al., 22

79

54

3.24

0.24

Chong et al.,23

81.8

58.8

2.12

0.33

Lim et al.,24

78.6

81.8

3.39

0.25

Wu et al., 25

78.6

73.3

5.74

0.57

Two studies authored by Lim et al. 24 and Chong et al.23 combined the results of the water swallowing test and the oxygen saturation test to create a “clinical” or “bedside” assessment tool, increasing the accuracy of the diagnosis of aspiration. The PPV increased to 3.43 in the study by Lim et al. 24 and to 2.51 in the Chong et al. 23 study.

The results of a recent systematic review by Martino et al. 20 evaluating the screening accuracy of 49 individual clinical screening tests for oropharyngeal dysphagia suggest that there is 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 benefits suggested a reduction in pneumonia, length of hospital stay, personnel costs and patients.

5.5.3 Risk Factors for Dysphagia Post ABI

What are the risk factors for dysphagia post ABI?

1.    Extent of brain injury

2.    Duration of coma 16

3.    Lower Glasgow Coma Score on admission (GCS 3-5) 9

4.    Severity of CT Scan findings 4

5.    Duration of mechanical ventilation 4

6.    Tracheostomy

7.    Translaryngeal (endotracheal) intubation

8.    Severe cognitive and cognition disorders

9.    Physical damage to oral, pharyngeal, laryngeal and esophageal structures

10.  Oral and pharyngeal sensory difficulties.

Ward and Morgan6have identified a body of research which has attempted to define those factors which may affect the presence and severity of dysphagia post-TBI 4;5;9;26;27. Injuries that result from translaryngeal intubation or tracheostomy may contribute to swallowing dysfunction in TBI patients27. Morgan and Mackay27 also note that severe TBI patients with neurogenic dysphagia and a tracheostomy, are at particularly high-risk of aspiration. The negative effects can be minimized by ensuring the use of appropriately sized tracheostomy tubes and by avoiding overinflation of the cuff 28.  Passy-Muir (Positive Closure) Speaking Valves operated in the closed position can improve voice quality and speech production, while at the same time improve swallowing and reduce aspiration (Passy-Muir Clinical Inservice Outline 29).

5.5.4 Diagnosis of Aspiration Post ABI

What are the risk factors for aspiration post ABI?

The risk of dysphagia related aspiration is proportional to the initial severity of the head injury.  A history of a tracheostomy or mechanical ventilation may also be associated with increased risk of aspiration.  A summary of all risk factors is listed below:

1.    Lower GlasgowComa Score (3-5) 4

2.    Presence of a tracheostomy

3.    Poor cognitive functioning

4.    Hypoactive gag reflex

5.    Prolongued period of  mechanical ventilation 4

6.    Reduced pharyngeal sensation

7.    Brainstem involvement

8.    Difficulty swallowing oral secretions

9.    Coughing/throat clearing or wet, gurgly voice quality after swallowing water

10.  Choking more than once while drinking 50 ml of water

11.  Weak voice and cough

12.  Wet-hoarse voice quality

13.  Recurrent lower respiratory infections

14.  Low-grade fever or leukocytosis

15.  Auscultatory evidence of lower lobe congestion

16.  Immunocompromised state

Aspiration should be suspected when the ABI patient has any of the following: a complaint of trouble swallowing, an abnormal chest x-ray, congested vocal quality, or a delay in voluntary initiation of the swallow reflex and coughing during or after swallowing13. While all ABI patients are potential aspirators there are certain identifiable risk factors that have been recognized as greatly increasing the likelihood of aspiration. Initial severity of brain injury appears to be the strongest predictor of dysphagia related aspiration. Certain risk factors place patients at higher risk for aspiration. Initial severity of brain injury appears to be the strongest predictor of dysphagia related aspiration Additional factors which may also be strongly related to the severity of injury include the presence of a tracheostomy and the need for mechanical ventilatory support.

5.5.5 Videofluoroscopic Modified Barium Swallow (VMBS) Studies

Describe the importance of VMBS studies in the diagnosis of aspiration.

  1. Considered to be the “gold standard” in diagnosis of aspiration.
     
  2. Patients who aspirate over 10% of the test bolus or who have severe oral and/or pharyngeal motility problems are considered at high risk of pneumonia.
     
  3. May reveal the mechanism of the swallowing disorder.

When aspiration is suspected, the VMBS study is considered by some to be the “gold standard” in confirming the diagnosis14. A VMBS study examines the oral and pharyngeal phases of swallowing.  However, the patient must have sufficient cognitive and physical skills to undergo testing 30. 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.  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.

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 pneumonia31;32.  In many cases, it is difficult to practically assess whether 10% of more of the test bolus has been aspirated. 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 ABI patient.

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, immunocompromization, and underlying lung disease must also be considered.

Definitive criteria for determining indication for VMBS study have yet to be determined empirically. If a VMBS study is indicated and the result is positive, a second VMBS study may be appropriate in 1-3 months, if swallowing concerns persist.

5.5.6 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 1980s8. 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, is inexpensive and it may be performed at a patient’s bedside; however, research has shown the test may have a 50% false-negative error rate in the detection of aspirated material33-35. Belafsky et al.35in a study of 30 patients with tracheostomies conclude that the use of the MEBD test is beneficial with patients who have a tracheostomy tube (82% sensitivity) and in particular those who receive mechanical ventilation (100% sensitivity).

Brady et al. 34in a study looking at the effectiveness of the modified Evans blue dye test (MEBD) and the videofluoroscopic swallow (VMBS) found the MEBD 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.34 recommended that MEBD be followed by a VMBS to rule out the possibility of trace aspiration. Although this test is used in practice with those who sustain ABIs, no studies were found looking at its effectiveness with this population specifically. Similar findings were reported by Donzelli et al.33and O’Neil-Pirozzi et al.8. The Donezelli et al.33results indicate the MEBD test was unable to detect aspiration in trace amounts, thus confirming the 50% false-negative error rate. O’Neil-Pirozzi et al.8found 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.