Evaluating a novel Transcutaneous Auricular Vagus Nerve Stimulation control condition

Objective: Transcutaneous auricular vagus nerve stimulation (taVNS) is being actively explored as a therapeutic option for multiple conditions. Current blinding strategies employed in the literature are variable, and non-optimal due to perception confounds. Additional strategies are needed. We assessed the blinding integrity of taVNS when used with a novel sham waveform. Methods: Ten healthy subjects (mean age: 36.6 ± 11.3 y) completed a randomized, double-blind, parallel study. taVNS was delivered while participants performed tasks mimicking upper limb rehabilitative training. The intervention consisted of 6, thirty-minute sessions over 2 weeks. The blinding assessment was performed after the last session.   Results: Majority of the participants (n=6) were unsure of their stimulation allocation. The binomial test indicated no evidence of systematic unblinding based on guessing alone. Bang’s blinding index was -0.20 and -0.60 for the active and sham groups, respectively.  Discussion: This study's sham taVNS protocol indicates satisfactory participant blinding. Testing on larger samples and clinical populations is advocated to further demonstrate utility.