Neural Cardiovascular Function After Cervical Spinal Cord Injury

Maintenance of a stable blood pressure (BP) requires dynamic balance between the sympathetic and parasympathetic outflow to the cardiovascular effectors including the heart and the vasculature system. Beside a loss of motor and sensory functioning, hemodynamic instability is a common problem among individuals with SCI especially those occurring in the cervical region. Cardiovascular disorders associated with SCI limit individuals' participation in rehabilitation therapy and negatively impact other aspects of their lives. The aim of this study is to assess the capacity of neural control of BP regulation in individuals with cervical SCI at rest and in response to orthostatic stress. We used spectral power technique to quantify the neural regulation of cardiovascular function in 8 individual with cervical SCI, and 10 non-injured (NI) individuals. Low resting BP and a further decrease in BP with orthostatic stress were common in cervical SCI while heart rate (HR) was in normal range at rest, and significantly increased with stress. Low frequency spectral power of systolic BP was significantly low at rest, and increased with orthostatic stress in individual with motor incomplete SCI. Spectral power of HR, measure of parasympathetic activity, was also low in SCI indicating down regulation of parasympathetic activity, even though its pathways to the heart remain intact. Individuals with SCI are prone to have irregular breathing. Respiratory related oscillations may be augmented in BP and HR variability due to both irregularity and autonomic dysfunction.