Evoked pain analgesia in chronic pelvic pain patients using respiratory-gated auricular vagal afferent nerve stimulation
Pain Medicine, 05/11/2012

Napadow V et al. – Chronic pain disorders such as CPP are in great need of effective, nonpharmacological options for treatment. RAVANS produced promising antinociceptive effects for quantitative sensory testing (QST) outcomes reflective of the noted hyperalgesia and central sensitization in this patient population. Future studies should evaluate longer–term application of RAVANS to examine its effects on both QST outcomes and clinical pain.

• Counterbalanced, crossover study.
• Patients with chronic pelvic pain (CPP) due to endometriosis in a specialty pain clinic.
• Authors evaluated evoked pain analgesia for respiratory–gated auricular vagal afferent nerve stimulation (RAVANS) compared with nonvagal auricular stimulation (NVAS).
• RAVANS and NVAS were evaluated in separate sessions spaced at least 1 week apart.
• Outcome measures included deep–tissue pain intensity, temporal summation of pain, and anxiety ratings, which were assessed at baseline, during active stimulation, immediately following stimulation, and 15 minutes after stimulus cessation.

• RAVANS demonstrated a trend for reduced evoked pain intensity and temporal summation of mechanical pain, and significantly reduced anxiety in N = 15 CPP patients, compared with NVAS, with moderate to large effect sizes (η² > 0.2).