Comparison of the cough reflex test and water swallowing test in healthy participants and neurological patients

Comparison of the cough reflex test and water swallowing test in healthy participants and neurological patients. Background: Silent aspiration is poorly identified by traditional clinical swallowing evaluations. Recently, several studies have proposed the use of a cough reflex test (CRT) for screening patients at risk of aspirations. The first aim of this study is to investigate the CRT thresholds of citric acid concentration for identifying cough responses in healthy participants and neurological patients. The second aim is to compare the results of the CRT with the water swallowing test (WST), a standard screening test for identifying cough responses in neurological patients. Methods: The CRT and then the WST were administered to 100 neurological patients and 100 healthy participants. For the CRT, we administered incremental solutions of citric acid interspersed with placebo doses. We used the results of the CRT in healthy participants to define a citric acid concentration cut-off, which could be used with neurological patients as a screening for aspirations. Results: As all controls coughed at a concentration of 0.1 mol/L, this was used as a cut-off in patients to identify coughing as a screening for aspiration risk. Patients showed cough reflexes at concentrations significantly higher than controls (p=0.001). The WST was not administered to 17 patients, due to cognitive deficits and severe clinical conditions. Thirtysix patients had a cough response above the screening cut-off (> 0.1 mol/L), 25 of which (30.1%) also had a positive cough response during the WST. Conclusion: The CRT correlated significantly with the WST. Unlike the WST, the CRT could be easily administered to severely impaired patients. Our results indicate the use of the CRT as a screening test for silent aspirators.