Effect of suboccipital release on pain perception and autonomic reflex responses to ischemic and cold pain

Objective/Subjects. To determine the autonomic effects of suboccipital release (SOR) during experimentally induced pain, 16 healthy subjects (eight women, eight men) experienced ischemic (forearm postexercise muscle ischemia [PEMI]) and cold (cold pressor test [CPT]) pain. Design. Beat-to-beat heart rate (electrocardiogram), mean arterial blood pressure (finger photoplethysmography), baroreflex sensitivity (transfer function analysis), and pain perception were measured. SOR or a sham (modified yaw; 30 cycles/min) was performed in minute 2 of pain. Results. PEMI increased blood pressure by 23±2 and 20±2mmHg; no differences occurred between SOR or yaw. PEMI modestly elevated heart rate during ischemia, followed by significant reduction from baseline with SOR (-3±2 bpm) and yaw (-4±2 bpm); no differences were observed between treatments. CPT increased blood pressure (SOR=11±1, yaw=9±2mmHg) and heart rate (SOR=10±2, yaw=8±3 bpm) before SOR and yaw. Neither treatment nor sham blunted blood pressure increases (SOR=25±2, yaw=22±2mmHg) during CPT; both decreased heart rate (SOR = -3±2, yaw = -2±2 bpm) from baseline. PEMI and CPT caused increased pain without treatment modulation. Following pain and manual intervention, SOR increased baroreflex sensitivity in the 0.15-0.35 Hz range and decreased R-R interval power spectral density in the 0.03-0.5 Hz range compared with yaw. To probe potential mechanisms and interactions between manual treatment and a prototypic analgesic, oral aspirin (967 mg) was given 60 minutes before testing to reduce prostaglandin synthesis. Aspirin slightly attenuated pain but neither altered cardiovascular changes to PEMI nor interacted with SOR or yaw. Conclusions. SOR has the capacity to modulate paininduced autonomic control and regulation.