Analysis of Respiratory Muscle Strength Training in Amyotrophic Lateral Sclerosis (ALS) Patients: A Systematic Review

Respiratory muscle weakness is a significant contributor to morbidity and mortality in amyotrophic lateral sclerosis (ALS) patients. Respiratory muscle strength training (RMST) has emerged as a potential therapeutic approach to mitigate respiratory muscle weakness in ALS. Still, its efficacy and safety remain unclear due to conflicting evidence and methodological heterogeneity in existing studies. A systematic review was conducted across three databases (PubMed (United States National Library of Medicine, Bethesda, MD, USA), Embase (Elsevier, Amsterdam, Netherlands), and Cochrane Library (Cochrane, Alberta, Canada)) following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to assess the effectiveness of RMST in ALS patients. Eligible studies included comparative studies for RMST, focusing on outcomes such as maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), forced vital capacity (FVC), and ALS Functional Rating Scale (ALSFRS-R). Quality assessment was performed using the Cochrane Risk of Bias tool. This study included six studies, including 183 patients with a mean age of 58.0 years (49.6 to 63.2) and a mean follow-up time of 21.2 weeks (eight to 52). The average mean difference for ALSFRS-R (three studies), MIP (three studies), MEP (three studies), and FVC (two studies) were 2.062 (0.04 to 5.3), 2.285 (-8.145 to 10.8), 19.435 (10.86 to 21.7), and 7.23 (3.6 to 10.86), respectively. Complications related to RMST were poorly reported across studies. Secondary outcomes, such as depression scores, blood oxygen levels, and heart rate variability, showed promising trends but lacked consistency. Despite positive findings on respiratory muscle strength, RMST's efficacy in ALS management remains inconclusive. Challenges include methodological heterogeneity, limited sample sizes, and inadequate reporting of complications. Future research should focus on standardized protocols, larger sample sizes, longer follow-ups, and comprehensive assessment of adverse effects to clarify the role of RMST in ALS treatment.