5.5 Pneumonia and Aspiration Post ABI

The presence of aspiration alone is not sufficient to cause pneumonia.  Aspiration of small amounts of saliva occurs during sleep in almost half of normal subjects (Finegold, 1991; Huxley et al., 1978). 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). 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 sample of severe traumatic brain injured individuals.

5.5.1 Defining Aspiration Pneumonia

In the absence of studies specific to ABI, we rely on the stroke literature to provide examples of criteria used previously to define aspiration pneumonia.  Clinical criteria vary between studies and affect the reported incidence (Table 5.12). 

Table 5.4 Criteria for Defining Aspiration Pneumonia in Stroke

Johnson et al. (1993), defined pneumonia as x-ray evidence of segmental consolidation, infiltrates or recorded respiratory difficulty with segmental moist rales on chest auscultation, plus two of the following supporting signs and symptoms: temperature elevation >100 °F, white blood cell count greater than 10,000, or evidence of hypoxia. Teasell et al. (1996) used similar criteria to make a diagnosis of pneumonia based upon radiological evidence of consolidation/infiltration and at least one other feature of granulocytosis, increased temperature (> 380C) and/or shortness of breath.  In contrast, Kidd et al. (1995) utilized the concept of a lower respiratory tract infection which they defined as “the production of sputum in conjunction with the development of crackles on auscultation, with or without the presence of fever or leucocytosis.”  Smithard et al. (1996) defined “chest infection” as the presence of two or more of the following: tachypnea (>22/min), tachycardia, inspiratory crackles, bronchial breathing, and use of antibiotics.

5.5.2 Relationship Between Pneumonia and Dysphagia/Aspiration

In stroke, an association between pneumonia and dysphagia/aspiration has been reasonably well-established (Tables 5.13 and 5.14). The presence of dysphagia and aspiration has been associated with increased odds of pneumonia. One study conducted recently by Hansen et al. (2008) examined association within the ABI population. 

Individual Study

Table 5.5 The Relationship Between Pneumonia, GCS and FIM Scores Post ABI

D&B = Downs and Black (1998) quality assessment scale score.

Discussion

In one study conducted by Hansen et al. (2008), they found 27% of those admitted to the brain injury unit had pneumonia, and other 12% developed pneumonia during their stay. Of those who developed pneumonia, 81% were receiving nothing by mouth (NPO). Another 14%, even though they were still being tube fed, developed pneumonia following attempts to give them food or fluids orally. Those who were admitted with low GCS (<9), FIM (<19) scores and RLAS scores (<3) were significantly more likely to develop pneumonia (p<0.01) than those admitted with higher scores. 

Conclusions

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

There is Level 4 evidence indicating those with a lower GCS, FIM scores and RLA scores are more likely to develop pneumonia while being tube fed.