Non-invasive assessment of autonomic nervous system integrity in able-bodied and spinal cord-injured individuals

The purpose of this study is to identify features of the Valsalva maneuver (VM) that differentiate between able-bodied (AB, n = 14) and spinal cord-injured individuals with high (T, n = 11) and low (P, n = 10) lesions. The systolic blood pressure (BP) recovery during the VM was used as a measure of sympathetic and vagal activity, whereas from the BP rise in phase IV of the VM baroreflex sensitivity was derived. After a similar initial BP decrease in all groups, BP recovered faster and more completely in AB compared to P and T during the VM. After release of the VM, the BP overshoot was very similar in AB and P, suggesting that the BP overshoot reflects sympathetic activity onto the heart, The baroreflex sensitivity was smaller in P, but not in T, compared to AB, However, 36% of the observations of T had such a low correlation between BP and RR interval that a slope could not be determined, which caused loss of observations, but suggested a low baroreflex sensitivity as well.