5.4 Aspiration Post ABI
Aspiration is defined as “entry of material into the airway below the level of the true vocal cords”. Since many patients with dysphagia do not aspirate, the two terms are not synonymous, although they are closely associated. When assessing the patient for signs of aspiration a videofluoroscopic swallowing study (VFSS/VFS) 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. The terms VFSS, VFS or MBS are often used interchangeably; however, for this chapter we will attempt to use the term VMBS.
5.4.1 Incidence of Aspiration Post-ABI
Studies examining the incidence of aspiration after an ABI are summarized in Table 5.3.
Individual Studies
Table 5.3 Incidence of Aspiration Post-ABI
Author/ Year/ Country/ |
Methods |
Outcomes |
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Terre & Mearin (2009)
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N=26 Patients who had sustained a severe TBI and had a VMBS diagnosis of aspiration were included in the study. Oropharyngeal dysphagia was diagnosed following an assessment of swallowing, tongue function, labial function, and coughing during feeding. Videofluoroscopic (VFS or VMBS) examinations and an evaluation of oropharyngeal dysphagia were conducted following the administration of various liquids or foods of differing consistencies at time of admission, 1, 3, 6 and 12 months post admission. |
Results of the VMBS or VFS and oropharyngeal dysphagia examinations showed that the number of patients with aspiration events decreased from their initial assessment to the final assessment at 12 months. Overall at the start of the study, tongue dysfunction was noted in over 50% of the patients, some had a delayed swallowing reflex and 33% were silent aspirators. To assist with swallowing, dietary changes were implemented in 92% of the patients. |
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O’Neil-Pirozzi et al., |
N=12 Prospective blinded comparative study of acute trached TBI inpatients, either in a vegetative state (RLA level II) or a minimally responsive state (RLA level III) admitted acutely to a rehabilitation hospital. |
All 12 subjects were able to successfully complete the test. 3 (25%) of patients aspirated. All 3 of these aspirated silently.
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Mackay et al., (1999b) |
N=54 Prospective evaluation of patients with severe head injury consecutively admitted to an acute trauma centre. Patients were included only if they were sufficiently cognitively intact to enable a VMBS swallowing evaluation. |
33 (61%) of patients demonstrated one or more swallowing impairments on VMBS examination. 22(41%) patients aspirated. The GCS scores of aspirators were lower than for non-aspirators. |
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Schurr et al., (1999)
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N=47 Retrospective review of patients who had been referred for a swallowing evaluation while an inpatient at a rehabilitation facility for severe TBI. The average GCS score was 8. Patients received a bedside evaluation and patients with abnormal findings also received a VMBS. |
31 patients received a VFSS test. The VMBS was abnormal in 22/31 (71%) patients. 13 patients had either laryngeal penetration or minor aspiration which were responsive to dysphagia therapy and patients could be fed orally. 9 patients demonstrated either gross (n=4) or silent (n=5) aspiration and required non-oral feeding. |
Discussion
Terre and Mearin (2009) evaluated aspiration improvements in 26 patients at 1, 3, 6, and 12 months post ABI. Videofluoroscopic (VFS) results indicate that aspiration decreased for the majority of patients during the 12 month period following their injury. For the majority of patients the most significant changes were seen at the 3 month evaluation period.
O’Neil-Pirozzi et al. (2003) studied 12 patients all of whom were trached. Patients successfully completed a modified barium swallow (VMBS). Only 3 patients aspirated on some of the various liquids introduced to the patients. These three patients were either in a minimally responsive state or a vegetative state at the time of testing. All patients were given various oral exercises, or taste and thermal stimulation to improve swallowing.
Mackay et al. (1999b) performed a series of VMBS studies on 54 young severely brain injured patients, an average of 17.6 days post-injury and noted a 61% incidence of dysphagia. Of these patients 41% aspirated. Other swallowing abnormalities included loss of bolus control (79%), reduced lingual control (79%), and decreased tongue base retraction (61%) delayed trigger of swallowing reflex (48%), reduced laryngeal closure (45%), reduced laryngeal elevation (36%), unilateral pharyngeal paralysis (24%), absent swallow reflex (6%) and cricopharyngeal dysfunction (3%) (Mackay et al.,1999b).
Schurr et al. (1999) conducted beside evaluations in 47 patients. Of these, 31 were admitted to the VMBS study. VMBS results indicate that 22 of the 31 patients aspirated during feeding. Five patients had laryngeal penetration and aspiration was observed in another 8. All responded to a modified diet.
Conclusion
The incidence of aspiration post-ABI occurs in approximately 30 to 50% of ABI patients with dysphagia. This represents 10-20% of rehabilitation admissions.
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Post ABI, aspiration can be seen in 30 to 50% of patients with dysphagia.
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5.4.2 Silent Aspiration
Aspiration cannot always be diagnosed by a bedside examination. Patients may aspirate without outward signs. “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). Detailed clinical swallowing assessments were shown to under diagnose or to miss cases of aspiration (Horner & Massey, 1988; Horner et al., 1988; Splaingard et al.,1988). Silent aspirators were considered to be at increased risk of developing more serious complications such as pneumonia. Silent aspiration should be suspected in the ABI patient with 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. Lazarus and Logemann (1987) identified aspiration in 38% of their ABI patient group, noting many of these patients, despite aspirating, did not produce a reflexive cough and they required prompting to clear aspirated material. In a more recent study by Terre and Mearin (2009), they found approximately 33% of their subjects were silent aspirators. Dietary changes were made to reduce the risk of aspirating. For many, issues with aspiration seemed to resolve within the 12 months of the study.
Conclusions
The incidence of silent aspiration in ABI patients has not been well documented. Such cases may be missed in the absence of VMBS studies.
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Silent aspiration is not uncommon and benefits from VMBS to detect.
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