Evoked Pain Analgesia in Chronic Pelvic Pain Patients using Respiratory-gated Auricular Vagal Afferent Nerve Stimulation

I medisinsk sammenheng benyttes ofte elektrisk stimuli i øret for å styrke vagusnerven gjennom dens forbindelse til huden i øret. I denne studien viser de at vagus nerven stimuleres best om man synkroniserer stimulien med utpust. Denne kobler altså medisinsk stimuli med pustens stimuli. Men de har ingen oppmerksomhet på mulighetene ved å senke pustefrekvens samtidig.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3376238/

Chronic pain disorders such as CPP are in great need of effective, non-pharmacological options for treatment. RAVANS (Respiratory-gated Auricular Vagal Afferent Nerve Stimulation) produced promising anti-nociceptive effects for 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.

The analgesic mechanisms of VNS have not been fully elucidated, but are likely mediated by afferent (not efferent) input to supraspinal brain regions [16]. Vagal afference is relayed to the nucleus tractus solitarious (NTS) in the medullary brainstem. Importantly, the NTS also receives somatosensory afference via the auricular branch of the vagus (ABV) nerve from specific portions of the auricle [17]. ABV afference is transmitted to both the NTS [17] and the spinal trigeminal nucleus (SpV) [18], by neurons located in the superior (jugular) ganglion of the vagus nerve. Respiration can modulate NTS activity directly (the lungs are innervated by the vagus nerve) and indirectly. In regard to the latter, inspiration increases venous return to the thorax, which increases arterial pressure, and hence vagal (and glossopharyngeal n.) afference to the NTS via aortic and carotid baroreceptors, respectively [19]. The NTS then inhibits efferent vagal outflow to the heart [2021], leading to a transient inspiratory tachycardia with every breath. This feedback loop is termed “respiratory sinus arrhythmia” [22]. Hence, the dorsal medullary vagal system operates in tune with respiration, and we propose that supplying vagal afferent stimulation gated to the exhalation phase of respiration (i.e. when thoracic baroreceptor afference does not enter the NTS), will optimize t-VNS therapy (see Figure 1 for schematic). Furthermore, such intermittent, irregular stimulation (i.e., varying with respiration) will also mitigate classical neuronal adaptation/accomodation, which can occur with continuous stimulation of NTS neurons [23].

 

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