Assessing the capacity of the sympathetic nervous system to respond to a cardiovascular challenge in human spinal cord injury.
METHODS
Measurement of haemodynamic responses and cutaneous blood flow during an inspiratory-capacity apnoea following spinal cord injury (SCI).


OBJECTIVE
To assess the capacity of the sympathetic nervous system to respond to a cardiovascular challenge following SCI.


METHODS
Prince of Wales Medical Research Institute, Australia.


METHODS
Thirteen spinal cord injured subjects with injuries ranging from C5-T8 and eight able-bodied control subjects.


METHODS
Continuous blood pressure, an electrocardiogram, respiration and cutaneous blood flow were recorded during a static maximum inspiratory breath-hold for 40 s.


RESULTS
On average, systolic blood pressure decreased 26% from baseline in the spinal group during the breath-hold and remained below baseline throughout the entire apnoeic period. Heart rate in this group had an initial decrease from baseline but quickly increased throughout the breath-hold, being 17% above baseline in the recovery period. Systolic pressure in the control group decreased 12% from baseline at the beginning of the breath-hold but quickly stabilized for the remainder of the apnoea, with heart rate initially decreasing 22% and remaining below baseline throughout the breath-hold.


CONCLUSIONS
A maximal inspiratory breath-hold, which is known to cause a sustained increase in muscle sympathetic nerve activity, is a simple test to perform in supine spinal cord-injured subjects, and provides information on the capacity of muscle and splanchnic vasoconstrictor activity to increase blood pressure in SCI. A sustained decrease in blood pressure, coupled with an increase in heart rate, infers interruption of sympathetic vasoconstrictor pathways to muscle and splanchnic vascular beds.
Brown
R
R
Spinal Injuries Research Centre, Prince of Wales Medical Research Institute, Sydney, New South Wales, Australia. rach.brown@unsw.edu.au
Macefield
V G
VG
D001794:Blood Pressure / Q000502:physiology*; D004562:Electrocardiography / Q000379:methods; D006339:Heart Rate / Q000502:physiology*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D008451:Maximal Voluntary Ventilation / Q000502:physiology*; D010991:Plethysmography / Q000379:methods; D012039:Regional Blood Flow / Q000502:physiology; D012119:Respiration; D012867:Skin / Q000098:blood supply*; D013119:Spinal Cord Injuries / Q000473:pathology / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000503:physiopathology*