The Retornus-2 study: impact of respiratory muscle training in subacute stroke patients with dysphagia, study protocol of a double-blind randomized controlled trial

Background: Stroke can lead to varying degrees of oropharyngeal dysphagia, respiratory muscle dysfunction and even increase medical complications such as aspiration, malnutrition and death. Recent studies suggest that inspiratory and expiratory respiratory muscle training (IEMT) can improve swallowing efficacy and may reduce aspiration events. The main purpose of this study is to examine whether an 8-week IEMT programme can improve respiratory muscle strength and swallow dysfunction severity in subacute stroke patients with dysphagia. Methods: Retornus-2 is a two-arm, prospectively registered, randomized controlled study with blinded assessors and the participation of fifty individuals who have suffered a stroke. The intervention group undergoes IEMT training consisting of 5 sets of 10 repetitions, three times a day for 8 weeks. Training loads increase weekly. The control group undergoes a sham-IEMT protocol. The primary outcome examines the efficacy of the IEMT protocol to increase respiratory muscle strength and reduce dysphagia severity. The secondary outcome assesses the longitudinal impact of dysphagia on body composition and nutritional assessment over a 6-month follow-up. Discussion: IEMT induces an improvement in respiratory muscle strength and might be associated with relevant benefits in dysphagia patterns, as well as a reduction in the number of aspiration events confirmed by videofluoroscopy or fiberoptic endoscopic evaluation of swallowing. The description of the impact of swallowing impairment on nutritional status will help develop new strategies to face this known side-effect.