By Jane Guttendorf, DNP, CRNP, ACNP-BC, CCRN
Assistant Professor, Acute & Tertiary Care, University of Pittsburgh, School of Nursing
Dr. Guttendorf reports no financial relationships relevant to this field of study.
Impaired swallowing in patients with critical illness is estimated to occur in about 10-93% of patients.1-6 The sequela of impaired swallowing is aspiration, either overt or silent, with resulting risks for pneumonia, pneumonitis, acute lung injury, reintubation, malnutrition, and dehydration. Swallowing dysfunction is associated with increased length of stay and poor patient outcomes.5,6 Patients documented to have swallowing dysfunction incur additional risks related to placement of feeding tubes (nasogastric, nasoduodenal, percutaneous endoscopic gastrostomy) and prolonged enteral nutrition, which may further contribute to aspiration risk.
Swallowing dysfunction after critical illness is in part due to conditions present prior to ICU admission, including neuromuscular disorders (e.g., amyotrophic lateral sclerosis, cerebral palsy, multiple sclerosis, myasthenia gravis, muscular dystrophy, and Parkinson’s disease), cognitive dysfunction (e.g., Alzheimer’s disease and other dementias, psychiatric diagnoses), and preexisting physical conditions (e.g., head and neck cancer, esophageal disorders).
The elderly are more likely to experience swallowing difficulty. In one study of critically ill elderly patients intubated for ≥ 48 hours, researchers detected aspiration in 52% of patients (age > 65 years) as compared to 36% of patient controls (age < 65 years), and the elderly continued to exhibit persistent swallowing deficits at 2 weeks. In a multivariate analysis, only preadmission functional status was a determinant of delayed resolution of swallowing deficit (hazard ratio [HR], 1.68; 95% confidence interval [CI], 1.26-3.97).3
Additional factors related to the etiology for ICU admission and the course of critical illness may contribute to the development of subsequent swallowing dysfunction. For example, patients suffering stroke, facial burns or inhalation injury, trauma, acute alterations of mental status (such as delirium, weakness, and deconditioning), survivors of multiple system organ failure, sepsis, and particularly those experiencing prolonged intubation (usually defined as ≥ 7 days) are at higher risk of developing swallowing dysfunction.1,2,7
In one study of acute and long-term dysphagia in sepsis patients at 14 days, sepsis patients showed significantly more aspiration than non-sepsis patients
(P = 0.002). Both severe sepsis and tracheostomy were independent risk factors for severe dysphagia with aspiration at 14 days, and mortality at 4 months was significantly higher in the sepsis group (P = 0.006).7
The duration of intubation contributes significantly to the risk of developing swallowing dysfunction. Brodsky et al evaluated the association between patient-reported aspiration and the duration of endotracheal intubation in acute lung injury patients. In a multivariate regression analysis, duration of oral intubation was associated with dysphagia symptoms (HR, 1.79; 95% CI, 1.15-2.79) for the first 6 days, but additional days did not contribute additionally to dysphagia risk.8 Kim et al demonstrated similar findings in patients with non-neurologic critical illness. In a multivariate regression analysis, duration of endotracheal intubation was associated significantly with post-extubation aspiration (HR, 1.09; 95% CI, 1.01-1.18; P = 0.04).9
The number of patients treated with mechanical ventilation is significant and continues to increase each year. A retrospective cohort study to determine the incidence of mechanically ventilated patients in 1 year across six states demonstrated more than 180,000 patients received mechanical ventilation and more than 40% of those had intubations of > 96 hours.10 Given this high incidence of acute respiratory failure requiring intubation and mechanical ventilation, the associated burden of swallowing dysfunction in these patients also is expected to be proportionally high.
MECHANICS OF SWALLOWING
Swallowing is a complex function, requiring the coordinated effort of more than 30 muscles, innervated by several peripheral and cranial nerves, and interfaced with the swallowing center in the medulla of the brainstem.11 Swallowing is divided into four sequential phases: oral preparatory phase, oral transport phase, pharyngeal phase, and esophageal phase. A key portion of the swallowing process is to functionally protect the airway. During the pharyngeal phase, which is timed with the start of exhalation, respiration briefly ceases, the vocal folds close, and the epiglottis mobilizes to deflect the food bolus toward the esophagus.11 Aspiration of food or fluids into the airway can lead to pneumonia, pneumonitis, and acute lung injury, extensive morbidity, and even aspiration-associated mortality. When clinically apparent, aspiration is associated with coughing, sputtering, or choking while drinking or swallowing. However, often aspiration is not clinically apparent and presents as occult or “silent aspiration” with the same adverse consequences.
TESTS FOR THE EVALUATION OF SWALLOWING
Tests commonly used in the clinical setting to evaluate swallowing function include:
Provider-observed Water Swallow Test: Nurse or other bedside care provider observes the patient swallowing a small amount of water, and makes note of any evidence of aspiration (coughing, choking, sputtering).12
Bedside Swallow Evaluation (BSE): A speech language pathologist (SLP) performs a clinical bedside screening and evaluation, which involves a patient interview, directed physical exam, and evaluation for aspiration during bedside swallowing trials of different consistency liquids.12
One primary limitation to clinical BSE is that it can fail to identify silent aspiration, as this still relies on a patient developing a cough, gag, or gurgling sound upon aspiration. This prompts some clinicians to consider either a fiberoptic endoscopic evaluation of swallowing (FEES) or a modified barium swallow study (MBSS) in all patients considered to be at high risk of aspiration based on preexisting conditions or clinical conditions in the ICU (duration of intubation, mental status, etc.).
While there can be some variability in the BSE reliability, in one study of 16 burn patients, the clinical BSE was predictive of a subsequent abnormal modified barium swallow study.4 Eleven patients had an abnormal clinical swallow exam and underwent subsequent MBSS, which revealed abnormal swallowing in 10 of the 11 patients, identifying either oral dysphagia, pharyngeal dysphagia, esophageal dysphagia, or a combination.4
Fiberoptic Endoscopic Evaluation of Swallowing: Passage of a small caliber videoscope through the nares to visualize in real time the passage of food through the mouth, pharynx, larynx, and upper esophagus.12,13 FEES provides a view of the anatomic structures, secretion burden, secretion management, and the sensory function. Two primary advantages of the FEES over a MBSS are that the FEES exam can be performed at the bedside, and that it offers the additional benefit of evaluating vocal fold mobility, which is important for prevention of aspiration.
Modified Barium Swallow Study (also referred to as Videofluoroscopic Swallow Study [VFSS]): Under fluoroscopy, the patient swallows barium-containing foods/liquids per an established protocol for progression, with guidance by a SLP, and a radiologist reviews the videography. The MBSS provides better evaluation of the oral phase of swallowing and upper esophageal dysfunction than FEES, but is limited because it requires patient transport from the ICU to the radiology suite and exposes the patient to radiation.12,13
SCREENING AND EVALUATION OF SWALLOWING
Evaluation of swallowing usually proceeds in a tiered fashion. Soon after extubation and before beginning oral intake, patients are first screened for high-risk features for potential aspiration (e.g., preexisting conditions, prolonged intubation/mechanical ventilation, altered mental status). If deemed safe to do so, begin with a provider-observed water swallow test. If the patient fails the provider-observed swallow, a repeat evaluation can be performed within the next 12-24 hours. Significantly high-risk patients can bypass the water swallow test.
In patients deemed significantly high risk for aspiration based on initial screening, or in those failing the water swallow test, the next tier would be a BSE. Patients who pass the BSE without overt evidence of aspiration may be trialed with an oral diet. Patients who fail the BSE should be further evaluated with either a FEES or MBSS. A change in level of alertness should prompt reevaluation. Evaluation of swallowing should be a multi-disciplinary approach, involving nurses, advanced practice providers, physicians, and SLPs. Should swallowing difficulties occur, physicians may try other interventions, such as modification of dietary texture, position changes (chin tuck, head rotation), and other compensatory mechanisms to reduce risk during swallowing (employing multiple swallows, breath holding, etc.).12,13 An SLP should direct reevaluation for improvement and progression.
Given the growing numbers of mechanically ventilated patients and the high incidence of aspiration associated with swallowing dysfunction, maintaining a high index of suspicion for the presence of possible swallowing dysfunction is key for the clinician. Since there is wide variability in reports of the incidence of swallowing dysfunction, consider screening all patients who have been intubated, regardless of duration of intubation. Formally evaluate swallowing in all patients with high risk for dysfunction based on baseline clinical features as well as those with prolonged intubation, altered mental status, and significant risk for morbidity and mortality should aspiration ensue. Failure of the water swallow test and the BSE to detect silent aspiration should prompt a more definitive evaluation with either FEES or MBSS.
REFERENCES
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Barquist E, et al. Postextubation fiberoptic endoscopic evaluation of swallowing after prolonged endotracheal intubation: A randomized, prospective trial. Crit Care Med 2001;29:1710-1713.
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Leder SB, et al. Fiberoptic endoscopic documentation of the high incidence of aspiration following extubation in critically ill trauma patients. Dysphagia 1998;13:208-212.
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El Solh A, et al. Swallowing disorders post orotracheal intubation in the elderly. Intensive Care Med 2003;29:1451-1455.
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Edelman DA, et al. Bedside assessment of swallowing is predictive of an abnormal barium swallow examination. J Burn Care Res 2008;29:89-96.
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Macht M, et al. Postextubation dysphagia is persistent and associated with poor outcomes in survivors of critical illness. Crit Care 2011;15:R231.
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Macht M, et al. Post-extubation dysphagia is associated with longer hospitalization in survivors of critical illness with neurologic impairment. Crit Care 2013;17:R119.
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Zielske J, et al. Acute and long-term dysphagia in critically ill patients with severe sepsis: Results of a prospective controlled observational study. Eur Arch Otorhinolaryngol 2014;271:3085-3093.
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Brodsky MB, et al. Duration of oral endotracheal intubation is associated with dysphagia symptoms in acute lung injury patients. J Crit Care 2014;29:574-579.
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Kim MJ, et al. Associations between prolonged intubation and developing post-extubation dysphagia and aspiration pneumonia in non-neurologic critically ill patients. Ann Rehabil Med 2015;39:763-771.
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Shaw S, Martino R. The normal swallow: Muscular and neurophysiological control. Otolaryngol Clin N Am 2013;46:937-956.
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Macht M, et al. Swallowing dysfunction after critical illness. Chest 2014;146:1681-1689.
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Brady S, Donzelli J. The modified barium swallow and the functional endoscopic evaluation of swallowing. Otolaryngol Clin N Am 2013;46:1009-1022.
