A Pilot Study of the Breath Stacking Technique Associated with Respiratory Muscle Endurance Training in Patients with Amyotrophic Lateral Sclerosis: Videofluoroscopic Findings in the Upper Airway

Introduction: Bulbar impairment represents a hallmark feature of amyotrophic lateral sclerosis (ALS) that significantly impacts survival and quality of life. Respiratory complications arise because of the weakness of the upper airway and respiratory muscles leading to respiratory failure, impaired swallowing, and reduced airway safety. Breath stacking and respiratory muscle endurance training are techniques that have been described to improve respiratory and bulbar function in patients with ALS. Considering the above, a respiratory technique named TR3 was developed. This study aimed to measure the acute effects of this technique on the upper airway through videofluoroscopy and to assess its clinical trial feasibility in patients with ALS. Material andmethods: In this cross-sectional study, we enrolled participants diagnosed with ALS to perform a single session of TR3. Epidemiological data and baseline assessments were collected. The assessments included kinematics from videofluoroscopy measuring the retropalatal airspace size, the size of the narrowest airway, and the pharyngeal area during rest and TR3. Results: Eight participants were included. During TR3, an acute increase of 15% was observed in the retropalatal airspace size (t = 5.14, p < 0.01), a 123% increase was observed in the size of the narrowest airway (t = –4.18, p < 0.001), and a 277% increase was observed in the pharyngeal area (t = –5.34, p < 0.001). Conclusions: During the intervention, TR3 showed acute effects in increasing pharyngeal constriction, pharyngeal expansion, retropalatal airspace size, and post-lingual narrowest airway size and is feasible for a larger research program. A clinical trial (NCT04226144) is already being conducted to assess the chronic therapeutic effects of this technique and its impact on the clinical evolution of ALS.