EFFICACY OF RESPIRATORY MUSCLE TRAINING ON MUSCLE STRENGTH AND PULMONARY FUNCTION IN INDIVIDUALS WITH SPINAL CORD INJURY – A SYSTEMATIC REVIEW

S.-J. Lin¹, I. Marshall¹, M. Lopez¹, D. Anderle¹, J. Roos², M. Johnson¹

¹Texas Woman's University Dallas Campus, School of Physical Therapy, Dallas, United States, ²Fresno State University, Department of Physical Therapy, Fresno, California, United States

Background: Declines in respiratory muscle strength and pulmonary function are common sequelae following spinal cord injury (SCI). Such declines can lead to impaired cough, reduced airway clearance and increased risk of pulmonary complications such as aspiration pneumonia. Respiratory muscle training (RMT) may reduce these risks and enhance quality of life.

Purpose: The purpose of this study was to systematically review available evidence on the efficacy of RMT on respiratory muscle strength and pulmonary function for individuals with SCI.

Methods: A literature search was conducted using databases including PubMed, Cochrane, and CINAHL Complete. The inclusion criteria for article selection were: (1) individuals with SCI (at cervical and thoracic level), (2) outcomes on pulmonary functional test (e.g., forced vital capacity, forced expiratory volume in one second, peak expiratory flow rate, maximal inspiratory pressure (PImax), and/or maximal expiratory pressure (PEmax)), and (3) study designs including cohort studies with pre-/post- assessments, and randomized controlled trials (RCT). Exclusion criteria for article selection consisted of: (1) written in languages other than English, (2) with multiple interventions, and (3) case reports and case series. Two researchers independently screened the literature and extracted the eligible articles. The methodological rigor was assessed with the Physiotherapy Evidence Database (PEDro) scale for RCTs. Descriptive statistics were used for data analysis. Meta-analysis with the R software is ongoing.

Results: Six cohort studies and eighteen RCTs published between 1986 to 2021 were included. Eight studies assessed both Inspiratory muscle training (IMT) and expiratory muscle training (EMT) and one study assessed only EMT. A total of 24 studies with 534 participants met the inclusion criteria for this systematic review. Participants included individuals with SCI at the cervical and thoracic levels. Time since injury ranged from the acute stage to the chronic stage. The average methodological rigor of the studies on the PEDro scale was 7 (+/- 1.6) out of 11 points. The experimental settings included: acute care, home, outpatient facilities, inpatient rehabilitation facilities, specialized SCI units, and institutions for the disabled. Mostly, the RMT protocols included 1-2 sessions per day, 5-7 days per week for 4 weeks to 4 months. Typically, starting exercise intensity was set at 30% (or 60%) PImax and was increased weekly. Two types of training devices were used among the studies: resistive or pressure threshold type. Significant improvements in PImax and/or PEmax were reported in 21 studies, while improvements in pulmonary function were reported in 15 studies.

Conclusions: Our findings demonstrated that RMT is effective for individuals with SCI and could improve pulmonary function and inspiratory (or expiratory) muscle strength, potentially improving quality of life in individuals with SCI. The rigor of RMT studies was fair to good; however, these studies were mostly limited by an unblinded study design and a small sample size. Therefore, high-quality studies with better design and larger sample sizes are warranted in future studies.

Implications: In view of the risk of respiratory complications in individuals living with SCI and mostly positive effects observed from respiratory muscle training in this review, RMT could be encouraged in individuals with SCI.

Funding acknowledgements: None

Keywords:
Spinal cord injury
Maximal inspiratory pressure
Maximal expiratory pressure

Topics:
Neurology: spinal cord injury
Cardiorespiratory

Did this work require ethics approval? No

Reason: This study was a systematic review.