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The Effects of Transcutaneous Vagal Nerve Stimulation on Dynamic Cerebral Autoregulation
Author(s) -
Ryan Caleb T.,
Pereira Felipe G.,
Picking Haley,
Schlader Zachary J.,
Johnson Blair D.
Publication year - 2022
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2022.36.s1.r5318
Subject(s) - medicine , middle cerebral artery , vagus nerve stimulation , anesthesia , transcranial doppler , photoplethysmogram , mean arterial pressure , vagus nerve , blood pressure , cerebral autoregulation , transcutaneous electrical nerve stimulation , cardiology , heart rate , stimulation , autoregulation , ischemia , alternative medicine , filter (signal processing) , pathology , computer science , computer vision
Purpose Transcutaneous vagal nerve stimulation (tVNS) applied to the cervical branch of the vagus nerve is FDA‐approved to treat migraine and cluster headache. tVNS applied to the auricle branch of the vagus nerve (tVNS ab ) reduces muscle sympathetic nerve activity and improves cardiac parasympathetic activity after one session in healthy participants. Given the use of tVNS to treat cerebral disorders and its effects on autonomic function, we postulated that tVNS ab might be beneficial for cerebral vascular function. We tested the hypotheses that tVNS ab will increase resting middle cerebral artery blood flow velocity (MCAv) and improve dynamic cerebral autoregulation (dCA) during a repeated squat‐to‐stand procedure. Methods Seven healthy participants (age: 20 ± 3 y; BMI:19 ± 7 kg/m 2 ; 3 women) completed two randomized experimental visits on separate days. One visit consisted of tVNS ab using a transcutaneous electrical nerve stimulation device (pulse width = 200 ms; pulse frequency = 30 Hz) with electrodes attached to the tragus of each ear. A time‐control visit (SHAM) was conducted with electrodes attached to the tragus but no current was applied. Mean arterial pressure (MAP; photoplethysmography), the partial pressure of end‐tidal carbon dioxide (PETCO 2 ; capnography) and MCAv (transcranial Doppler ultrasound) were measured continuously. After 45 min of resting tVNS or SHAM, subjects performed a repeated squat‐to‐stand maneuver at a frequency of 0.05 Hz for 5 min while tVNS ab or SHAM continued. Resting conductance values for the MCA (MCAc) were calculated as MCAv/MAP. MCA dCA was assessed during the squat‐to‐stand maneuver using spectral analyses to obtain coherence, gain, and phase values in the very low frequency (VLF) and low frequency (LF) bands. Spectral analysis gain was also assessed using normalized units (gain n ), defined as beat to beat values divided by the mean value relative to changes in blood pressure. Data are presented as mean ± SD. Results There were no differences between tVNS ab and SHAM for MAP (tVNS ab : 103 ± 8; SHAM: 102 ± 12 mmHg; P=0.41), PETCO 2 (tVNS ab : 35 ± 5; SHAM: 36 ± 2 mmHg; P=0.42), MCAv (tVNS ab : 61.5 ± 9.2; SHAM: 58.7 ± 13.3 cm/s, P=0.36) or MCAc (tVNS ab : 0.60 ± 0.08; SHAM: 0.59 ± 0.19 cm/s/mmHg, P=0.46) during baseline. There were no differences between conditions for coherence at VLF (tVNS ab : 0.43 ± 0.14; SHAM: 0.45 ± 0.34; P=0.44) or LF (tVNS ab : 0.65 ± 0.17; SHAM: 0.72 ± 0.13; P=0.06). Phase in the VLF (tVNS ab : 0.35 ± 0.32; SHAM: 0.33 ± 0.36 rad; P=0.44) and LF (tVNS ab : 0.28 ± 0.23; SHAM: 0.30 ± 0.16 rad; P=0.36) were not different. Gain (tVNS ab : 0.56 ± 0.30; SHAM: 0.56 ± 0.54 cm/s/mmHg; P=0.50) and gain n (tVNS ab : 0.99 ± 0.53; SHAM: 0.85 ± 0.84 %/mmHg; P=0.37) in the VLF were not different. However, gain (tVNS ab : 0.76 ± 0.14; SHAM: 0.86 ± 0.17 cm/s/mmHg; P=0.02) and gain n (tVNS ab : 1.22 ± 0.16; SHAM: 1.35 ± 0.23 %/mmHg; P=0.04) in the LF were lower during tVNS ab . Conclusion tVNS ab did not alter resting cerebral vascular responses. However, MCA LF gain was lower during tVNS ab versus SHAM. These preliminary data indicate that dCA in a major intracranial cerebral artery might be improved during a single session of tVNS ab . Further research regarding the influence of chronic tVNS ab on cerebral vascular function is warranted.