Difficulty clearing mucus, pulmonary embolism, reduced lung capacity, respiratory failure or pneumonia are the main respiratory complications which can occur after a SCI and continue to be one of the leading causes of morbidity and mortality in this population, especially among cervical and higher thoracic injuries. Many risk factors for respiratory problems include completeness of the injury, higher level of injury, or more severe injury, among others. The present review has shown the evidence regarding different therapies and programs for the treatment of respiratory problems in patients with SCI, showing in general a lack of high-quality studies in form of RCTs, while the majority are retrospective or pre-post (without control group) studies.
Regarding the pharmacological options, there is some evidence that different types of medications (such bronchodilators, anabolic agents, or anxiolytics) could have beneficial effects in pulmonary function in patients with SCI. Despite this, there is a need for more quality of evidence as only one study was a high level of evidence (RCT) in this area.
Exercise training of the upper and lower limbs and respiratory exercise are the fields with the largest and the best evidence in this area. While both exercise training regimens have shown beneficial effects in functionality, respiratory function, and respiratory muscle strength of patients with SCI; the ideal training protocols and dosage remain unclear because there is abundant heterogenicity among studies.
Assistive devices and other treatments like abdominal binders, chest wall vibration and immersion seem to improve respiratory function, but more and high-quality studies are needed to provide more robust conclusion and determine the long-term effects in patients with SCI.
Sleep disordered breathing, commonly known as sleep apnea appears to have a higher prevalence in people after SCI, but despite this high prevalence, there are few studies in this area. Only CPAP therapy has proven beneficial clinical effects to treat SDB in people with SCI, while other treatments with medications could not show clinical effects until this date.
ES interventions for the restoration of inspiratory muscle function in people with SCI include bilateral phrenic nerve pacing, bilateral diaphragmatic pacing and combined intercostal muscle stimulation with unilateral phrenic pacing (DiMarco 2005). From the study by Glenn and colleagues in the 1970s, the scientific evidence has been increased. Despite a large number of studies in the area, and the beneficial effects of phrenic nerve and diaphragmatic stimulation as an alternative to MV, there is still a need for more high-quality studies as the majority of them are pre-post studies or case series.
People with SCI are at risk for secretion retention because of an increased prevalence of pneumonia compounded by lower expiratory flows during cough. Secretion removal techniques are common practice in this population and yet there is predominantly only level 4 evidence to support the use of some airway clearance techniques to facilitate secretion removal in patients with SCI, but until this date, there is no evidence of one airway clearance technique over another, and in the same way, there are no criteria available to indicate when to implement the various airway clearance techniques.
The approach to ventilator weaning in SCI remains an important and somewhat neglected issue. There is a distinct lack of controlled trials in respiratory medicine; again, research in this area primarily consists of retrospective reviews and small case series. There is some evidence of different ventilator and weaning protocols are beneficial in the improvement of respiratory parameters, successful weaning, and successful switch to non-invasive ventilation, but prospective studies on mechanical and weaning protocols are required to determine the best way to assess, treat and wean people requiring MV following SCI.