Acute physiological and electrical accentuation of vagal tone has no effect on pain or gastrointestinal motility in chronic pancreatitis

Abstract

BackgroundThe effective management of pain in chronic pancreatitis (CP) remains a therapeutic challenge. Analgesic drugs, such as opioids, and the underlying pathology can impair gut function. The autonomic nervous system influences hormone secretion and gut motility. In healthy volunteers, electrical (using noninvasive transcutaneous vagal nerve stimulation [t-VNS]) and physiological (using deep slow breathing [DSB]) modulation of parasympathetic tone results in pain attenuation and enhanced gut motility. Thus, the aims were to investigate whether t-VNS and DSB could enhance the parasympathetic tone, decrease pain sensitivity and improve gut motility in CP.Patients and methodsA total of 20 patients (12 males, mean age=61 years, range: 50–78 years) with CP were randomized to short-term (60 minutes) t-VNS and DSB, or their placebo equivalent, in a crossover design. Cardiometrically derived parameters of autonomic tone, quantitative sensory testing of bone and muscle pain pressure, conditioned pain modulation (CPM) and assessments of gastroduodenal motility with ultrasound were performed.ResultsIn comparison to sham, t-VNS and DSB increased cardiac vagal tone (CVT) (P<0.001). However, no changes in pain pressure thresholds for bone (P=0.95) or muscle (P=0.45) were seen. There was diminished CPM (P=0.04), and no changes in gastroduodenal motility were observed (P=0.3).ConclusionThis explorative study demonstrated that t-VNS and DSB increased CVT in patients with CP. However, this short-lasting increase did not affect pain sensitivity to musculoskeletal pain or gastroduodenal motility. The chronic pain in CP patients is complex, and future trials optimizing neuromodulation for pain relief and improved motility are needed.

Motivational nondirective resonance breathing versus transcutaneous vagus nerve stimulation in the treatment of fibromyalgia: study protocol for a randomized controlled trial

“…Active and sham treatment allocation is concealed from the participants and testing administrators. Both testing administrators and study participants will be told that they will provide/receive two different versions of nerve stimulation at different locations on the ear (for the tVNS group) or that there are two breathing techniques that are being explored (for the MNRB group) in this investigation [ 53 ]. The testing administrators will introduce either “Version 1” (active) or “Version 2” (sham) of the treatment interventions.…”

Motivational nondirective resonance breathing versus transcutaneous vagus nerve stimulation in the treatment of fibromyalgia: study protocol for a randomized controlled trial

“…Active and sham treatment allocation is concealed from the participants and testing administrators. Both testing administrators and study participants will be told that they will provide/ receive two different versions of nerve stimulation at different locations on the ear (for the tVNS group) or that there are two breathing techniques that are being explored (for the MNRB group) in this investigation [33]. The testing administrators will introduce either "Version 1" (Active) or "Version 2" (Sham) of the treatment interventions.…”

“…Participants are instructed not to talk or make any movements during their treatment session. Participants will be instructed to breathe at the normal respiration rate for an adult (12 breadths/ min) [45] by following a respiratory pacer [46] on the Krüger&Matz Flow 5 Android MNRB™ program while counting their breadth [33]. Out of a full (100%) breathing cycle, participants are instructed to breathe normally with a 49% inhale and a 49% exhale without any (i.e.…”

“…During CV I, participants will familiarize themselves with the stimulation device and its proper usage under the guidance of the testing administrator. During this visitation, the intensity of the tVNS will be slowly increased until the optimal intensity (mA) is reached (i.e., a slightly uncomfortable tingling sensation) for each individual participant [33]. Both active and sham stimulation constantly alternate between active stimulation for 30 s, followed by a break of 30s [108].…”

“…Even though it is typically considered unfeasible to blind the experimenter to the intervention for investigations of this kind, it has been recommended [101] that studies document expectation bias by carefully designing and standardizing the intervention instructions and measuring participants' expectations about the effectiveness of the to-bedelivered intervention-both of which are exercised in this study. Nonetheless, the di culty in designing a reliable sham breathing protocol for experimental and clinical trials is quite apparent-trials that implement sham breathing protocols commonly instruct participants to either "breathe normally" [33] or "spontaneously breathe" [102] while "focusing on their breadth" [103]. Longitudinal research [104] comparing daily variations of time and frequency-based HRV parameters between controlled breathing (i.e.…”