Infection control in cough reflex testing: An equipment-based bacterial contamination study

Abstract

Cough reflex testing evaluates the sensory integrity of the laryngeal cough reflex and has recently been applied for the evaluation of patients with dysphagia. It involves brief nebulization of citric acid through a sterile reservoir, mask, and tubing which are disposed of after use. Nebulizers used for drug delivery or humidification are reported to become contaminated with bacteria, leading to patient colonization and consequently increasing the risk of chest infection. No research has been undertaken to evaluate whether nebulization used for cough reflex testing poses similar threats. This study analyzed whether pathogens colonize in the disposable products used for cough reflex testing in the short duration of usual clinical practice as a component of the clinical swallowing assessment. Samples taken from both ends of the tubing, the reservoir and the mask, pre- and post-nebulization, were smeared onto blood agar plates, then incubated at 37°C in candle jars. After 48 hours the plates were removed and bacterial colonies were counted. No colonies grew from either end of the tubing for any trial. Evidence of bacterial colonization was found in samples from the reservoir and the mask and single-tailed paired t tests were completed for these datasets. For the reservoir and the mask data, there were no significant differences between pre- and post-nebulization bacteria counts. These results suggested that the clinical methods used for cough reflex testing do not result in significant colonization of bacteria on test materials.