Differences Between Silent And Non-Silent Aspiration

Nutrition Research Newsletter, Jan, 2000 by C. Smith, J. Logemann, L. Coangelo

Healthy individuals may take for granted the ability to swallow. Swallowing is a normal and safe activity in the majority of the population. However, for those inflicted with dysphagia, swallowing may result in foreign materials entering the airway, causing aspiration. Normally, when materials are aspirated they result in a cough to expectorate the foreign material from the air passages. However, silent aspiration resulting in no cough mechanism is at times seen in dysphagic individuals. Previous research suggests that the etiology of aspiration does not appear to be related to whether this condition is silent or not silent.

A recent retrospective study set out to examine the frequency of the cough response in aspirators identified through the use of videofluoroscopy. Eleven hundred patients in two urban acute care hospitals were examined using videofluoroscopy over a two-year period. The variables reviewed included age, gender, and medical diagnosis. An additional goal was to determine the differences between individuals who aspirated only one time during the swallow and those who aspirated more than one time during the same swallow. It was hypothesized that those individuals who aspirated more than one time during a given swallow would be more prone to cough than those who aspirated only once during the swallow.

Four hundred sixty-nine, or 43%, of the individuals studied were identified as aspirating. Two hundred seventy-six, or 59%, of the aspirating patients aspirated silently, without coughing. It was found that age, gender, and medical diagnosis were significantly associated with silent aspiration in the group of individuals who aspirated once during a swallow. The timing of aspiration and the etiology of aspiration were not found to be significantly associated with whether a cough was present. There were no significant associations found in the group of patients who aspirated more than one time during a swallow to the variables examined. There was a high incidence of silent aspiration among the youngest age group ([is less than] 19 years of age). The etiology of dysphagia in this group was primarily neurologic causes. The higher incidence of silent aspiration among those with neurological impairment may be due to the higher incidence of sensory loss seen in this population than seen in the groups with other medical diagnoses. At the other end of the spectrum, the oldest age group ([is greater than] 70 years of age) also had a high proportion of silent aspirators. It is known that sensory loss commonly occurs with aging. Men were found to be more likely to aspirate than were women. Other characteristics that may affect aspiration, such as smoking history, were not included in this analysis.

These findings suggest that silent aspiration is more common in the youngest and eldest age groups, in men, and in those with neurologic impairment. These findings can be helpful in identifying silent aspiration in an acute care setting.

C. Smith, J. Logemann, L. Coangelo, et al., Incidence and patient characteristics associated with silent aspiration in the acute care setting. Dysphagia 14:1-7 (December 1999) [Correspondence: Christina H. Smith, M. Sc., Dept. of Communication Sciences and Disorders, Northwestern University, 2299 N. Campus Dr., Evanston, IL 60208]