Respiratory Training Improves Blood Pressure Regulation in Individuals With Chronic Spinal Cord Injury

Abstract Objective To investigate the effects of respiratory motor training (RMT) on pulmonary function and orthostatic stress–mediated cardiovascular and autonomic responses in individuals with chronic spinal cord injury (SCI). Design Before-after intervention case-controlled clinical study. Setting SCI research center and outpatient rehabilitation unit. Participants A sample of (N=21) individuals with chronic SCI ranging from C 3 to T 2 diagnosed with orthostatic hypotension (OH) (n=11) and healthy, noninjured controls (n=10). Interventions A total of 21±2 sessions of pressure threshold inspiratory-expiratory RMT performed 5d/wk during a 1-month period. Main Outcome Measures Standard pulmonary function test: forced vital capacity, forced expiratory volume in one second, maximal inspiratory pressure, maximal expiratory pressure, beat-to-beat arterial blood pressure, heart rate, and respiratory rate were acquired during the orthostatic sit-up stress test before and after the RMT program. Results Completion of RMT intervention abolished OH in 7 of 11 individuals. Forced vital capacity, low-frequency component of power spectral density of blood pressure and heart rate oscillations, baroreflex effectiveness, and cross-correlations between blood pressure, heart rate, and respiratory rate during the orthostatic challenge were significantly improved, approaching levels observed in noninjured individuals. These findings indicate increased sympathetic activation and baroreflex effectiveness in association with improved respiratory-cardiovascular interactions in response to the sudden decrease in blood pressure. Conclusions Respiratory training increases respiratory capacity and improves orthostatic stress–mediated respiratory, cardiovascular, and autonomic responses, suggesting that this intervention can be an efficacious therapy for managing OH after SCI.