People with spinal cord injury are at risk for retention of secretions because of an increased prevalence of pneumonia compounded by lower expiratory flows during cough, which is greatest during the acute phase after SCI. Increased prevalence of respiratory infections, although decreased during the rehabilitation phase of recovery, is still higher in people with SCI compared to age-matched healthy people. Reduction in expiratory flows during cough is related to the higher levels of SCI. Of considerable surprise, several devices that have been shown to be effective in people with other chronic respiratory conditions have not been evaluated in people with spinal cord injury.
Very few studies have examined the effectiveness of secretion removal techniques in people with SCI even though respiratory complications are a primary cause of morbidity and mortality in this population. With the exception of one RCT, studies performed to date are limited by a survey (Garstang et al. 2000) or lack of documentation of valid measurement technique of standard pulmonary function (Kang et al. 2006). Limited evidence supports the postulate that improving inspiratory muscle strength (Kang et al. 2006) in addition to expiratory muscle force (Estenne et al. 2000) are important to maximize expiratory flows during cough. IMT (Van Houtte et al. 2008), electrical stimulation of the expiratory muscles (Linder 1993; Estenne et al. 2000; DiMarco et al. 2009, Butler et al. 2011), and mechanical insufflation/exsufflation (the application of positive pressure to the airway, then shifting to negative pressure to produce an expiratory flow simulating a cough) as an adjunct to manual respiratory kinesitherapy (Pillastrini et al. 2006) are three potential therapies that can maximize the force produced by the inspiratory and expiratory muscles, respectively, in order to increase expiratory flows during cough. With the exception of the small RCT assessing the latter (Pillastrini et al. 2006), RCTs examining the effectiveness of airway clearance techniques in people after SCI are lacking. RMT (Van Houtte et al. 2008) and mechanical insufflations-exsufflation (Crew et al. 2010) has been shown to decrease infections and tended to decrease respiratory hospitalizations per year, respectively.
Other issues that require further study in SCI is to examine the effectiveness of hand-held devices that facilitate airway clearance, such as those that apply continuous (PeripepÒ) or oscillating positive expiratory pressure (Flutter). Of equal concern is to evaluate the comfort and preference of airway clearance techniques that are readily adhered to and performed by people with SCI. Some evidence supports the effectiveness of these positive expiratory pressure devices and other secretion removal techniques such as autogenic drainage in people with cystic fibrosis and other chronic respiratory diseases; however, the evidence to date is somewhat equivocal (Hess 2001; Reid & Chung 2004).
Secretion removal techniques are common practice in people with spinal cord injury and yet there is predominantly only level 4 evidence to support the use of some airway clearance techniques to facilitate secretion removal in this population. There is level 2 evidence (based on 2 RCTs) (Pillastrini et al. 2006; Jeong and Yoo 2015) in support of mechanical insufflation/exsufflation coupled with manual chest therapy kinesitherapy techniques.
There is no evidence in support of one airway clearance technique over another, and there are no criteria available to indicate when to implement the various airway clearance techniques.
There is a need to determine the most efficient and effective techniques that are comfortable and readily adhered to for people with SCI in order facilitate airway clearance, to improve their quality of life, and decrease health care costs.
- There is limited evidence that suggests that improving inspiratory and expiratory muscle force is important to maximize expiratory flow during cough.
- Cough effectiveness can be enhanced by a variety of methods including manual assistance by a caregiver, respiratory muscle training, and/or electrical stimulation triggered by the person with SCI.
- Hand-held expiratory pressure devices may enhance secretion removal in people with SCI.