Using electrical stimulation of the ear to change cough reflex sensitivity

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Neurological disease, such as stroke, has a devastating effect on sensation in the throat and the cough reflex. Without the ability to detect food or fluid from entering the lungs and eject it with a cough, stroke patients are at a high risk of developing chest infection. Chest infection is associated with prolonged hospitalisation, high death rate, and significant cost to the healthcare system. There are currently limited rehabilitation options available. Interestingly, probing the ear canal during a medical examination or having impacted ear wax can cause coughing. We propose to develop a protocol and explore the effect of using light electrical stimulation of the nerves within the outer ear (transcutaeneous auricular vagus nerve stimulation; taVNS) to improve cough sensitivity after stroke. Using a wearable device to stimulate the external ear has the potential of providing a portable, safe, non-invasive, and low-cost treatment for improving the cough reflex and boosting airway protection. The aim of this study is to find the optimal location and frequency of ear stimulation for improving cough reflex sensitivity in healthy participants. The effects of different stimulation frequencies (high vs. low), stimulation zone (ear canal vs. concha), and side of stimulation (right vs. left ear) on cough sensitivity will be investigated. The parameters in this study that result in the greatest decrease in citric acid cough threshold (i.e., greatest increase in cough sensitivity) will be used as the stimuluation parameters in a future randomised controlled trial investigating taVNS as a treatment for cough sensitivity in individuals with neurological disorders.