Twenty-four studies were included in the review: two randomised controlled trials, three prospective controlled studies, nine pre-post studies, three retrospective case series and seven case reports. Sample sizes ranged from one to 40. No information on quality assessment results was reported.
Secretion removal techniques (level 4 and 5 evidence): One case series and one case report demonstrated that mucus plugging in people with cervical spinal cord injury can be successfully managed with vigorous chest physiotherapy. Another case report found that the use of PARI PEP (an expiratory flow device) and inspiratory muscle training for one year decreased occurrence of respiratory infections, hospitalisation resulting from infection and suctioning.
Interventions affecting cough (levels of evidence ranged from 1 to 5): Two pre-post studies, one case series and two case reports found that glossopharyngeal breathing exercises (with or without neck accessory muscle breathing) improved cough in patients with cervical spinal cord injury (level 4 and 5 evidence). One prospective controlled trial and two pre-post studies (level 1 and 4 evidence) reported positive benefits for assisted breathing with the use of abdominal binders in patients with the same type of spinal cord injury. One case study and one high quality randomised controlled trial (14 participants) demonstrated that respiratory infections occurred less and that inspiratory muscle strength and endurance improved following use of inspiratory muscle training (level 1 and 5 evidence). Evidence from two pre-post studies and two case reports showed that electrical stimulation of the lower thoracic-lumbar spinal cord or abdominal wall muscles helped to improve expiratory flow rates during cough (level 4 and 5 evidence). Two prospective controlled trials and one pre-post trial reported that manual abdominal compression led to improvements in cough expiratory flows (level 2 and 4 evidence).
Further results (including some data on adverse events) were reported in the review paper.