Aspiration Post ABI

When assessing the patient for signs of aspiration a videofluoroscopic swallowing study (VFSS) or, as it was later called, a modified barium swallow (MBS) may be undertaken. Each of these tests require the patient to swallow liquids or solids of various consistencies (from thin to thick, or thick to thin) and the path taken during the swallow maneuver is observed. This procedure allows for any structural or functional anomalies swallowing, along with any aspiration, to be observed.

Table: Incidence of Aspiration Post-ABI

Discussion

Rates of aspiration within the literature are variable, ranging from 25% to 71% depending on the sample surveyed (Mackay et al. 1999b; O'Neil-Pirozzi et al. 2003; Schurr et al. 1999). Terre and Mearin (2009) followed 26 patients with TBI who aspirated, 35% were silent aspirators, for one year. At 3, 6 and 12 months, the number of patients who aspirated continuously declined; aspiration was present in only 6 patients by the end of the first year (Terre & Mearin 2009). For the majority of patients the most significant changes were seen at the 3 month evaluation. Relating to assessment, O’Neil-Pirozzi et al. (2003) studied 12 tracheostomized patients with severely disordered consciousness and found that the MBS was successfully completed with all of them; consequently these patients with TBI are potential MBS candidates.  A study by Steele et al. (2013) found that patients had improvements on measures of tongue pressure and penetration aspiration after the completion of a 24 session tongue-pressure resistance training program. The increased tongue strength is therefore beneficial in improving swallowing and isometric tasks.

 

 Post ABI aspiration improves in many patients over the first year, with many improving within the first three months post injury.

 

Risk Factors of Aspiration Post ABI

Aspiration should be suspected when the patient with an ABI 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 swallowing (Horner & Massey 1988). While all patients with ABI are potential aspirators, there are risk factors that place some patients at higher risk. Initial severity of the brain injury appears to be the strongest predictor of dysphagia related aspiration. Further, severe ABI patients with neurogenic dysphagia and a tracheostomy are at particularly high-risk of aspiration (Morgan & Mackay 1999). The negative effects can be minimized by ensuring the use of appropriately sized tracheostomy tubes and by avoiding over-inflation of the cuff (Tolep et al. 1996).

Table: Risk Factors for Aspiration Post ABI

  • Lower Glasgow Coma Score (3-5) (Mackay et al., 1999a)
  • Presence of a tracheostomy
  • Poor cognitive functioning
  • Hypoactive gag reflex
  • Prolonged period of  mechanical ventilation (Mackay et al., 1999a)
  • Reduced pharyngeal sensation
  • Brainstem involvement
  • Difficulty swallowing oral secretions
  • Coughing/throat clearing or wet/gurgly voice quality after swallowing water
  • Choking more than once while drinking 50 ml of water
  • Weak voice and cough
  • Wet-hoarse voice quality
  • Recurrent lower respiratory infections
  • Low-grade fever or leukocytosis
  • Auscultatory evidence of lower lobe congestion
  • Immunocompromised state

 

 

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.

 

Silent Aspiration

Aspiration cannot always be diagnosed by a bedside examination, as patients may aspirate without outward signs. Detailed clinical swallowing assessments have been shown to under diagnose or to miss cases of aspiration (Horner & Massey 1988; Splaingard et al. 1988). Silent aspiration is defined as “penetration of food below the level of the true vocal cords, without cough or any outward sign of difficulty” (Linden & Siebens 1983). Silent aspiration should be suspected in patients with ABI who have recurrent lower respiratory infections, chronic congestion, low-grade fever, or leukocytosis (Muller-Lissner et al. 1982). Clinical markers of silent aspiration may include a weak voice or cough, or a wet-hoarse vocal quality after swallowing. Silent aspirators are considered to be at increased risk of developing more serious complications such as pneumonia.

Lazarus and Logemann (1987) identified aspiration in 38% of their ABI sample and found many of these patients, despite aspirating, did not produce a reflexive cough and required prompting to clear aspirated material. In another study, approximately 33% of the subjects were silent aspirators and issues with aspiration seemed to resolve within the 12 months of the study (Terre & Mearin 2009).

 

The incidence of silent aspiration among individuals with ABI has not been well documented.

 

Silent aspiration may be missed in the absence of a modified barium swallow study.

 

Pneumonia and Aspiration Post ABI

Aspiration of small amounts of saliva occurs during sleep in almost half of healthy subjects (Finegold 1991; Huxley et al. 1978). The presence of aspiration alone is not sufficient to cause pneumonia. Aspiration pneumonia is thought to occur when the lung’s natural defenses are overwhelmed when excessive and/or toxic gastric contents are aspirated, leading to a localized infection or a chemical pneumonitis. Patients with reduced levels of consciousness, a tracheostomy, gastric reflux or emesis, nasogastric tubes (due to mechanical interference with the cardiac sphincter), or a compromised immune system are at increased risk for the development of aspiration pneumonia (Finegold 1991). In individuals with severe TBI, Langmore et al. (1998) identified dependence in self-feeding and oral-care, the amount of tooth decay, the need for tube feeding, greater than one medical diagnosis, smoking, and the total number of medications as the best predictors of pneumonia.  In a study by Vejdan and Khosravi (2013) significantly fewer patients with head injury experienced nosocomial pneumonia when they received flexible bronchoscopy and bronchoalveolar lavage in combination with routine methods compared to routine clearance procedures alone (14% versus 34%, p=0.03).

The clinical criteria used to define aspiration pneumonia vary between studies, impacting the reported incidence. In the absence of ABI specific studies, the criteria used within the stroke literature has been provided in the table below. 

Table: Criteria for Defining Aspiration Pneumonia in Stroke

Author/ Year

Country

Criteria

Carnaby et al. (2006)
USA;

 Dziewas et al. (2004)
Germany

Three of the following indicators: temp >38°C, productive cough with purulent sputum, abnormal respiratory exam including tachypnea, (>22 breaths/min), tachycardia, inspiratory crackles, bronchial breathing, abnormal chest x-ray, arterial hypoxemia (PO2 < 9.3 kPa) and positive chest radiography.

Teasell et al. (1996)
Canada

Radiological evidence of consolidation, and at least one other clinical feature including granulocytosis, temp >38°C and/or shortness of breath.

Smithard et al. (1996)
UK

Presence of at least two of the following: tachypnea (>22/min), tachycardia, aspiratory crackles, bronchial breathing or antibiotic usage.

Kidd et al.
(1995)
UK

Production of sputum in conjunction with the development of crackles on auscultation, with or without the presence of fever or leucocytosis.

DePippo et al. (1994);

Holas et al.
(1994)
USA

A positive chest x-ray or the presence of at least three of the following: temp > 100 °F, drop in PO2 > 10 torr, presence of WBC in sputum and/or positive sputum culture for pathogen.

Johnson et al. (1993)
USA

Segmental consolidation or infiltrate on chest x-ray or clinical diagnosis which included an episode of respiratory difficulty with segmental moist rales on auscultation and two other symptoms including temp >100 °F, WBC >10,000 or hypoxia.

The Relationship between Pneumonia and Dysphagia/Aspiration 

In stroke, an association between pneumonia and dysphagia/aspiration has been reasonably well-established. The presence of dysphagia and aspiration has been associated with increased odds of pneumonia. Further research in this area is needed within a TBI population.

Table: The Relationship Between Pneumonia, GCS and FIM Scores Post ABI

Discussion

In a retrospective sample of 173 patients with severe TBI, 27% of those admitted to the brain injury unit had pneumonia, and other 12% developed pneumonia during their stay (Hansen et al. 2008). Hansen et al. (2008) explored the risk factors associated with pneumonia. The study found that pneumonia was more common among individuals with low levels of consciousness and for those with a feeding or tracheotomy tube. As noted, Glasgow Coma Scale scores and Rancho Los Amigos scale scores were associated with risk of pneumonia, with individuals who had lower Glasgow Coma Scale scores being at high risk, as well as individuals with lower Rancho Los Amigo Scale scores.  These two scales, along with the Functional Oral Intake Scale and Functional Independence Measure scores were also found to be predictive of returning to an unrestricted diet (Hansen et al. 2008).

Conclusion

There is Level 4 evidence indicating that individuals with a low level of consciousness and those with tracheotomy tubes are at greater risk for pneumonia.

 

The risk of developing pneumonia appears to be proportional to the severity of the aspiration.