Usefulness of the Simplified Cough Test in Evaluating Cough Reflex Sensitivity as a Screening Test for Silent Aspiration

OBJECTIVE To assess cough reflex sensitivity using the simplified cough test (SCT) and to evaluate the usefulness of SCT to screen for silent aspiration. METHODS THE HEALTHY CONTROL GROUP WAS DIVIDED INTO TWO SUBGROUPS: the young (n=29, 33.44±9.99 years) and the elderly (n=30, 63.66±4.37 years). The dysphagic elderly group (n=101, 72.95±9.19 years) consisted of patients with dysphagia, who suffered from a disease involving central nervous system (ischemic stroke 47, intracerebral hemorrhage 27, traumatic brain injury 11, encephalitis 5, hypoxic brain damage 3, and Parkinson disease 8). The SCT was performed using the mist of a 1% citric acid from a portable nebulizer. The time from the start of the inhalation to the first cough was measured as the cough latency. All the dysphagic patients underwent the videofluoroscopic swallowing study. RESULTS The cough latency was more significantly prolonged in the healthy elderly group than in the healthy young group (p<0.001), and in the dysphagic elderly group than in the healthy elderly group (p<0.001). The sensitivity and specificity of SCT were 73.8% and 72.5% for detecting aspiration in the dysphagic patients, and 87.1% and 66.7% for detecting silent aspiration in the aspirated patients. CONCLUSION Cough latency measured with the SCT reflects the impairment of cough reflex in healthy elderly and dysphasic subjects. The results of this study show that the SCT test can be a valuable method of screening aspiration with or without cough in dysphasic patients.