Answers to readers’ questions on aspiration as a cause of cough

July 1, 2008
Carol Smith Hammond, PhD
Carol Smith Hammond, PhD

Volume 29, Issue 7

Cough can be a sign of aspiration in patients with dysphagia. Therefore, in evaluating patients with cough, the history should include a search for conditions associated with increased risk of impaired swallowing. These include conditions that require oropharyngeal suctioning, acute and degenerative neurological diseases (such as stroke, amyotrophic lateral sclerosis [ALS], and head trauma), cervical or brain surgery, head and neck cancer, and use of sedatives.1

 

Evaluating cough: The role of dysphagia and aspiration

When should aspiration be suspected in a patient with cough?

Cough can be a sign of aspiration in patients with dysphagia. Therefore, in evaluating patients with cough, the history should include a search for conditions associated with increased risk of impaired swallowing. These include conditions that require oropharyngeal suctioning, acute and degenerative neurological diseases (such as stroke, amyotrophic lateral sclerosis [ALS], and head trauma), cervical or brain surgery, head and neck cancer, and use of sedatives.1

In a number of studies, normal aging has been associated with impaired swallow function, thus placing the elderly at higher risk. Bedbound nursing home patients who are reliant on others for feeding and oral care are at increased risk for aspiration pneumonia.2-5

In one study of nursing home residents, total assistance for oral care and reliance on gastric tube feeding were found to be independent predictors of pneumonia.6 Among patients not requiring tube feedings, the likelihood of pneumonia was increased in those who were dependent for feeding, were current smokers, or were receiving more than 8 medications.6

An evaluation of swallowing is indicated for high-risk patients. Both videofluoroscopic evaluation performed in the radiology clinic and fiberoptic endoscopic evaluation of swallowing, which may be undertaken at the bedside, are considered the gold standard. The initial approach to identifying dysphagia is the clinical bedside evaluation of swallowing, performed by a speech-language pathologist.7 This evaluation has a number of components, including the subjective assessment of reflexive (involuntary) cough and voluntary cough.

Reflexive and voluntary cough

Both reflexive cough and voluntary cough have been associated with aspiration. Reflexive cough occurs in response to the presence of liquids or solid food in the laryngeal area and protects against tracheobronchial aspiration. Voluntary cough refers to cough that is produced on command and is not related to eating or drinking.

Cough that occurs while eating or drinking can be useful in identifying patients at risk for aspiration. In one study, witnessed aspiration was found to be one of the most important risk factors for pneumonia in a long-term–care facility.8 Therefore, subjective reports of coughing while eating or drinking should be ascertained from the patient, caregiver, or nurse.

McCullough and associates7 assessed the sensitivity and specificity of a clinical swallowing examination to detect aspiration-as identified by videofluoroscopic swallowing evaluation-in 165 patients with acute stroke. The clinical signs of aspiration included dysphonia, dysarthria, wet/gurgly voice, and nasal vocal resonance. The strength and quality of reflexive cough and voluntary cough were subjectively assessed.

The observation of coughing during or immediately after a 3-oz swallow was the single best measure for detecting aspiration.7 The global estimate of aspiration made by a trained speech-language pathologist after completing the clinical examination was useful in detecting aspiration; however, the clinical measures in general did not have adequate sensitivity. The sensitivity and specificity of some of the clinical measures used in this study are shown in the Table.

DeMatteo and associates9 compared clinical evaluation with videofluoroscopic examination of swallowing in children with feeding and swallowing problems. Clinical evaluation had a sensitivity of 92% for aspiration of fluids, but sensitivity was only 33% for solids. Cough was the most significant predictor of fluid aspiration and penetration.

The use of tussigenic challenge to assess the reflexive cough response to increasing concentrations of irritants is being studied as a predictor of aspiration.10-12 However, tussigenic challenge has not yet been studied in comparison with videofluoroscopic or fiberoptic endoscopic evaluation of swallowing.

Validated subjective reports of a weak voluntary cough as a predictor of aspiration in patients with acute stroke are mixed. One study found that voluntary cough was of limited value in screening stroke patients for the risk of aspiration pneumonia.13 The investigators studied 30 patients with acute middle cerebral artery distribution stroke. They found that patients with left middle cerebral artery infarctions were more likely to have cough apraxia (inability to cough on command, or absent or incoordinated phases of cough).

We studied airflow patterns of voluntary cough in patients with acute stroke and found that such patterns were associated with aspiration risk.14 This method is being studied in other at-risk groups.

Silent aspiration

In the syndrome of silent aspiration, reflexive cough does not occur when swallowed material contacts or passes the true vocal folds into the proximal trachea. One study of older adults (mean age, 66 years) found that the risk of pneumonia was increased 4-fold in patients with penetration of material into the laryngeal area during swallowing on videofluoroscopy (P = .008).15 The risk was increased 10-fold in those with tracheobronchial aspiration (P = .0001) and 13-fold in those with silent aspiration (P = .0001).15

A retrospective review of medical records was performed for 1101 patients referred to a speech-language pathologist for feeding or swallowing evaluation.16 Of those who aspirated on videofluoroscopic evaluation, 59% (276 of 469) were silent aspirators. These persons ranged in age from 3 to 98 years and had a variety of medical conditions, which included head and neck cancer, ALS, stroke, Parkinson disease, cerebral palsy, spinal cord injury, closed head injury, brain tumor, and GI problems. Variables significantly associated with silent aspiration included age (P < .0001), male gender(P < .004), and medical diagnosis (neurological impairment, GI problems, and unknown cause; P < .05).

Management

The possible complications of abnormal swallowing include malnutrition, dehydration, bronchospasm, and airway obstruction, as well as aspiration pneumonia and bronchitis. The symptoms of dysphagia, such as coughing and choking at mealtime, may have secondary outcomes, such as social isolation and depression.

Therapy for dysphagia in patients with acute stroke has been associated with a significant reduction in swallowing-related medical complications (relative risk [RR], 0.73; 95% confidence interval [CI], 0.6 to 0.9), chest infection (RR, 0.56; 95% CI, 0.4 to 0.8), and death or institutionalization (RR, 0.73; 95% CI, 0.55 to 0.97), and a significant increase in the proportion of patients regaining swallowing function by 6 months (RR, 1.41; 95% CI, 1.03 to 1.94).17

Conclusions 

Dysphagia should be included in the differential diagnosis of cough, and the medical history should alert clinicians that aspiration may be the cause of cough. An evaluation of swallowing is indicated for high-risk patients. Videofluoroscopy and flexible endoscopy are critical components of the swallowing evaluation, since the sensitivity and specificity of subjective assessment ofcough alone are insufficient to guide dietary modifications to avoid aspiration.