Incidence and patient characteristics associated with silent aspiration in the acute care setting.

Coughing is a physiologic response to aspiration in normal healthy individuals. However, there are published records that report no cough in response to aspiration (i.e., silent aspiration) in dysphagic patients. In this retrospective study, for more than 2 years in two acute care hospitals we examined frequency of the cough response in patients identified as aspirators by using videofluoroscopy. One thousand one hundred one patients underwent videofluorographic evaluation of their swallowing during this 2-year period; 469 aspirated; 276 were silently aspirating. Two hundred twenty-four of these silent aspirators aspirated once during a swallow and 52 silently aspirated more than once during a swallow. These two groups of patients were analyzed separately. Univariate (chi-square and Fisher's exact tests) and multivariate (logistic regression) analyses were conducted to assess the relationship of silent aspiration to age, gender, medical diagnosis, timing of aspiration, and etiology of aspiration. In univariate analysis, age (p < 0.001), gender (p < 0.004), and medical diagnosis (p = 0.05) were significantly associated with silent aspiration in the group who aspirated once during a swallow. No significant associations were seen in the group of patients who aspirated more than once during a swallow.