Respiratory Muscle Training
Acute physiotherapy is an emerging non-invasive option to help patients resume normal pulmonary functioning and timely discharge. Early prophylactic treatment in the form of physiotherapy has been shown to improve diaphragm function and reduce secretions in patients with acute SCI (McMichan et al. 1980). Assisted coughing, intermittent positive pressure breathing, and regular changes in body positioning are some of the techniques used to help keep patients’ airways clear and breathing independently (Berney et al. 2002). In addition, breathing exercises and diaphragm strengthening can also improve lung functioning and assist in weaning from mechanical ventilation. Resistive inspiratory muscle training (RIMT) and abdominal weights training (Gross et al. 1980; Lin et al. 1999) as well as cough training combined with functional electrical stimulation (McBain et al. 2013) are techniques that have been implemented for physiotherapy in chronic patients with SCI. RIMT (Derrickson et al. 1992; Postma et al. 2014; Raab et al. 2019), expiratory resistive muscle training (Roth et al. 2010), respiratory (inspiratory and expiratory) muscle training (Boswell-Ruys et al. 2020; Sikka et al. 2021), abdominal weights training (Derrickson et al. 1992), normocapnic hyperpnea training (Van Houtte et al. 2008), isocapnic hyperpnea (Mueller et al. 2012; 2013), and complex interventions (self-directed RMT consisting in glossopharyngeal breathing exercises, IMT using incentive spirometry, and air stacking exercises with a resuscitation bag) (Shin et al. 2019) have been studied in the acute SCI population and are reviewed below.
Figure 6. The Breather® Respiratory Muscle Trainer
Discussion
A Cochrane review and meta-analysis demonstrated that RMT training in the hospital (including IMT, EMT, isocapnic hyperpnea, among other types of respiratory training) can significantly improve respiratory muscle strength, function, and endurance for people with tetraplegia (as measured by vital capacity, maximal voluntary ventilation, inspiratory capacity, MIP, and MEP). (Berlowitz & Tamplin 2013; Tamplin & Berlowitz 2014).
Eight RCTs have examined the effectiveness of physiotherapy techniques on the pulmonary function of patients with SCI. Boswell-Ruys et al. (2020) found that RMT (IMT and EMT) provided more improvements in MIP, respiratory health, and Borg scores for breathlessness during 10 inspiratory loaded breaths compared to the same exercises using a sham device in 62 patients with acute or chronic tetraplegia. A study of 96 patients by Sikka et al. (2021) suggested that resistive IMT (using a threshold trainer imposing resistance to inspiration and expiration) resulted in a significant positive effect on pulmonary function and on respiratory muscle strength compared to the control group. Mueller et al. (2012 & 2013) evaluated 24 participants with complete tetraplegia in three groups (sham, isocapnic hyperpnea and inspiratory resistive training). After eight weeks of training, patients who performed isocapnic hyperpnea and inspiratory resistive training obtained significantly better results in inspiratory muscle strength and different components of quality of life, compared to those who were training with placebo. Liaw et al. (2000) studied 30 participants with acute SCI and found that the group who performed a target resistive inspiratory muscle training twice a day for 6 weeks showed a greater change in VC and TLC in the IMT group compared to the change in control values, whereas MIP improved in both groups. Postma et al. (2014) investigated the effect of RIMT in people with SCI during inpatient rehabilitation. This technique was found to have a positive short-term effect on inspiratory muscle function one week following the intervention period; however, this effect was no longer significant eight weeks post muscle training. Finally, Roth et al. (2010) assessed the effectiveness of expiratory muscle training compared to sham training in patients with acute SCI. Multivariate analysis did not reveal any significant between-group differences for any pulmonary function tests conducted after the 6-week training period.
A case-control study also found positive results with both inspiratory and combination in- and expiratory muscle training regardless of AIS score (Raab et al. 2018). Measures of inspiratory and expiratory pressure significantly increased, as well as forced vital capacity regardless of muscle training group (Raab et al. 2018). Another study with patients with acute SCI found that IMT, starting about six weeks after injury for six consecutive weeks with a gradual increase in the intensity, provided an increase in MIP and MEP. The association of MIP with training intensity was independent of AIS and lesion level, whereas the effect of training intensity on MEP showed differences between groups; participants with motor complete lesions (AIS A/B) showed a 6.8% (95% CI 2.1 to 11.7%) increase in MEP per 10 units (cmH2O) of increase in training intensity, compared with participants with motor incomplete lesions (AIS C/D) who the increase was 0.1% (95% CI −4.3 to 4.5%) (Raab et al. 2019). The pre-post study of McDonald & Stiller (2019) assessed 7 patients with acute SCI who performed a protocol of IMT consisting of a high-resistance and low repetition, with progressive increase of training load (until 90% MIP) for 4 weeks. They showed no adverse safety outcomes and improvements in lung function in four of the seven participants.
A case control study (Berney et al. 2002) has shown that extubation along with initiation of intensive physiotherapy can improve lung function, reduce the rate of pulmonary complications and decrease the length of stay in intensive care for patients with acute tetraplegia. It should be noted that patients who have been extubated or who have had a tracheostomy are able to receive physiotherapy, if treatment occurs once the patient is in stable condition.
Physiotherapy treatments during acute SCI would be useful for stable patients and in hospitals that have the resources for on-call physiotherapists. Prospective large-scale RCTs should continue to be conducted to confirm these findings that physiotherapy is an effective adjuvant to improve acute pulmonary functioning.
Conclusion
There is level 1b evidence (from four RCTs: Mueller et al. 2012 & 2013; Postma et al. 2014; Liaw et al. 2000; Derrickson et al. 1992), level 3 evidence (from three case-control studies: Raab et al. 2019; Raab et al. 2018; Shin et al. 2019), and level 4 evidence (from one pre-post study: McDonald & Stiller 2019) in support of inspiratory muscle training as an effective means to improve respiratory muscle function compared to usual care in patients with acute SCI regardless of AIS score.
There is level 1a evidence (from two RCTs: Boswell-Ruys et al. 2020; Sikka et al. 2021) that respiratory muscular training (imposing resistance to inspiration and expiration) improves respiratory muscle strength and pulmonary function in patients with acute SCI.
There is level 1b (from one RCT: Van Houtte et al. 2008) that normocapnic hyperpnea training provided a significant increase in respiratory muscle strength and endurance, pulmonary function, and decrease the rate of respiratory infections in patients with acute SCI.
There is level 3 evidence (from one case control: Berney et al. 2002) that extubation and intensive physiotherapy reduces length of stay in intensive care in patients with acute SCI.
