Respiratory muscle training in people with cervical spinal cord injury – A systematic review

INTRODUCTION: Spinal cord injury is a physiological disruption often caused by trauma, leading to severe physical and psychological effects, including irreversible impairment and disability. Cervical injuries, particularly between C1 and C8, are the most severe, potentially causing diaphragm paralysis and requiring mechanical ventilation. Reduced respiratory muscle strength not only affects respiratory function but also significantly impacts voice, speech, and communication, which are crucial for quality of life. OBJECTIVE: Conduct a systematic review of the literature on respiratory muscle training protocols in individuals with cervical spinal cord injury and evaluate the methodological quality of scientific publications. METHODS: Studies were searched by two independent researchers in the Regional Portal of the Virtual Health Library, EMBASE, SCOPUS and PubMed databases, using the descriptors: "respiratory muscle strength", "breathing training", and "cervical spinal cord injury", with no restriction on the time of publication. Studies containing respiratory muscle strength measurements and respiratory muscle training in people with cervical SCI were included and those that associated other techniques with functional respiratory training, such as electrical stimulation and other complementary techniques were excluded. The studies had the methodological quality (internal and external validity) classified by the PEDro scale (Physiotherapy Evidence Database). RESULTS: Nine studies were identified and considered valid based on the inclusion criteria. The protocols presented varied parameters. The session time ranged from 15 to 45 minutes, the number of sessions per day ranged from 1 to 2, the number of days per week ranged from 3 to 7, and the number of intervention weeks ranged from 4 to 10. Only three studies presented internal and external validity for respiratory muscle training programs. CONCLUSION: This review identified that respiratory muscle training is an effective intervention to improve respiratory function in people with cervical SCI. However, due to the poor methodological quality of the studies, the effect size of the treatment, as well as the ideal dose and intensity, requires further investigation to better determine its overall effectiveness.