Restoration of cough via spinal cord stimulation improves pulmonary function in tetraplegics

Abstract

Background: Spinal cord injury (SCI) results in significant loss in pulmonary function secondary to respiratory muscle paralysis. Retention of secretions and atelectasis and, recurrent respiratory tract infections may also impact pulmonary function. Objective: To determine whether usage of lower thoracic spinal cord stimulation (SCS) to restore cough may improve spontaneous pulmonary function in individuals with chronic SCI. Design/Methods: 10 tetraplegics utilized SCS system on a regular daily basis. Spontaneous inspiratory capacity (IC), maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP) were measured at baseline prior to usage of the device and repeated every 4-5 weeks over a 20-week period. Maximum airway pressure generation (P) during SCS (40 V, 50 Hz, 0.2 ms) at total lung capacity (TLC) with subject maximal expiratory effort, at the same timepoints were determined, as well. Results: Following daily use of SCS, mean IC improved from 1636 ± 229 to 1932 ± 239 ml (127 ± 8% of baseline values) after 20 weeks (P < 0.05). Mean MIP increased from 40 ± 7, to 50 ± 8 cmH2O (127 ± 6% of baseline values) after 20 weeks, respectively (P < 0.05). MEP also improved from 27 ± 3.7 to 33 ± 5 (127 ± 14% of baseline values) (NS). During SCS, P increased from baseline in all participants from mean 87 ± 8 cmH2O to 117 ± 14 cmH2O at weeks 20, during TLC with subject maximal expiratory effort, respectively (P < 0.05). Each subject stated that they experienced much greater ease in raising secretions with use of SCS. Conclusion: Our findings indicate that use of SCS not only improves expiratory muscle function to restore cough but also results in improvement inspiratory function, as well.

Keywords: Cough; Pulmonary function; Rehabilitation; Spinal cord stimulation.

Figures

Figure 1

Mean changes in airway pressure generation during use of SCS (40 V, 50 Hz, 0.2 ms) at TLC with subject maximal expiratory effort during baseline and after 10 and 20 weeks of daily of use of SCS. Regular usage of SCS resulted in an increase in positive expiratory pressure generation overtime. *P 

Figure 1

Mean changes in airway pressure generation during use of SCS (40 V, 50 Hz, 0.2 ms) at TLC with subject maximal expiratory effort during baseline and after 10 and 20 weeks of daily of use of SCS. Regular usage of SCS resulted in an increase in positive expiratory pressure generation overtime. *P 

Figure 2

Raw data of changes in inspiratory capacity (A) and maximum inspiratory pressure (B) during baseline and at the 9- and 16-week time points in one subject.

Figure 2

Raw data of changes in inspiratory capacity (A) and maximum inspiratory pressure (B) during baseline and at the 9- and 16-week time points in one subject.

Figure 3

Mean changes in IC, MIP and spontaneous MEP after 20 weeks of daily use of SCS. *P 

Figure 3

Mean changes in IC, MIP and spontaneous MEP after 20 weeks of daily use of SCS. *P 

Figure 4

Mean changes in inspiratory capacity (IC; top panel), maximum inspiratory pressure (MIP; middle panel) and maximum expiratory pressure (MEP; lower panel) expressed as a percentage of baseline values at the 5-, 10-, 15- and 20-week time points. *P 

Figure 4

Mean changes in inspiratory capacity (IC; top panel), maximum inspiratory pressure (MIP; middle panel) and maximum expiratory pressure (MEP; lower panel) expressed as a percentage of baseline values at the 5-, 10-, 15- and 20-week time points. *P 

Figure 5

Relationship between airway pressure generation during use of SCS at TLC with subject effort and, inspiratory capacity (IC; left panel panel) and maximum inspiratory pressure (MIP; right panel) at week #20. There was a highly significant linear correlation between these parameters (P 

Figure 5

Relationship between airway pressure generation during use of SCS at TLC with subject effort and, inspiratory capacity (IC; left panel panel) and maximum inspiratory pressure (MIP; right panel) at week #20. There was a highly significant linear correlation between these parameters (P