Effects of Expiratory Muscle Strength Training on Airway Protection and Swallowing in Chronic Dysphagia After Radiation Therapy

Radiation therapy for head and neck cancer (HNC) is associated with the development of swallowing difficulties, or dysphagia. Dysphagia has profound negative effects on the health, nutritional status, and quality of life of HNC survivors. It also puts them at risk of developing life-threatening aspiration pneumonia. Radiation-associated dysphagia can be intractable and not responsive to conventional dysphagia therapy. HNC survivors with chronic severe dysphagia may be dependent on long-term tube feeding. Expiratory Muscle Strength Training (EMST) is a low-cost, device-driven therapy. It has been studied as an approach to simultaneously improve cough and swallowing functions. During EMST, patients forcefully expire into a one-way spring-loaded valve to strengthen expiratory and submental musculature. The EMST-150 device is available for clinical use in Singapore. In other research studies, it has been shown to improve cough and swallowing in several populations of people with chronic dysphagia, most recently in people with chronic radiation-associated dysphagia. The investigators propose to study the effect of EMST using the EMST-150 device on cough, airway protection, and swallowing functions of HNC survivors with radiation-associated dysphagia. The investigators will recruit 40 participants to undergo an 8-week EMST programme, with weekly follow-up to calibrate their EMST device. It is hypothesised that EMST will improve participants' respiratory and swallowing functions. Respiratory function improvement will be shown by increased maximum expiratory pressure and improved cough airflow measures. Swallowing function improvement will be evidenced by reduced aspiration or improved ability to clear aspirated material during videofluoroscopic swallow studies. The investigators also hypothesize carryover effects on other aspects of swallowing, such as improved hyoid and laryngeal excursions, and improved laryngeal vestibule closure. With the results of this study, the