The effects of inspiratory muscle training on inspiratory muscle strength, lung function and quality of life in adults with spinal cord injuries: a systematic review and Meta-analysis

Purpose This systematic review and meta-analysis aimed to evaluate the effectiveness of inspiratory muscle training (IMT) on respiratory muscle strength, lung function and quality of life (QOL) in adults with spinal cord injuries (SCI). Methods Databases were searched up to June 2022; CENTRAL, CINAHL, MEDLINE, PEDRo, and PubMed. Following PRISMA reporting guidelines, two independent reviewers selected studies and extracted data. Study quality and levels of evidence were assessed. Results Following selection from 624 initial search results, six randomised controlled trials were identified, comprising 124 participants. Quality of Evidence was very low to moderate. Meta-analysis showed that post intervention, IMT significantly improved maximal inspiratory pressure (MD 15.72 cmH2O, 95% CI 5.02, 26.41, p = 0.004) when compared with a control intervention. There was no significant benefit for physical QOL (SMD 0.12, 95% CI -1.01, 1.25, p = 0.84), mental QOL (SMD -0.2, 95% CI -1.72, 1.33, p = 0.80), maximal expiratory pressure (MD 5.19 cmH2O, 95% CI -4.16, 14.55, p = 0.80), or FEV1 (MD 0.26 L, 95% CI -0.19, 0.7, p = 0.26). Sensitivity analyses found larger effects for studies with 8 week interventions (MD 17.5 cmH2O (95% CI 3.36 to 31.66)) and spring loaded devices alone (MD 21.18 cmH2O, 95% CI 9.65 to 32.72). Conclusion Moderate quality evidence suggests IMT improves respiratory strength in adults with an SCI. The mental and physical QOL outcomes provided very low quality of evidence, with considerable heterogeneity between study results, leading to inconsistency. Further research is warranted to investigate medium and long-term impact of robust IMT protocols, accounting for patient motivation and adherence to IMT.