The Efficacy and Mechanisms of Transcutaneous Auricular Vagus Nerve Stimulation on Abdominal Pain and Other Symptoms in Patients With Constipation-predominant Irritable Bowel Syndrome
Phase: NA
Conditions: Constipation-predominant Irritable Bowel Syndrome, Abdominal Pain
Sponsor: Tongji University

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Clinical study protocol 
Protocol Title: The efficacy and mechanisms of transcutaneous auricular vagus nerve stimulation on 
symptoms in patients with constipation-predominant irritable bowel syndrome 
NCT NUMBER: NCT05392439  
Document Date: 5/25/2022 
Principal Investigator: Xiaodan Shi 
Sponsor: Shanghai East Hospital, Tongji University 
 
 
 

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Clinical study summary 
Title 
The efficacy and mechanisms of transcutaneous auricular vagus nerve 
stimulation on symptoms in patients with constipation-predominant 
irritable bowel syndrome  
Protocol number 
2020-006 
Sponsor 
Shanghai East Hospital, Tongji University  
Indication 
Constipation-predominant Irritable Bowel Syndrome (IBS-C) 
Objective/Aim 
This study aims to investigate the effects and possible mechanisms of 
transcutaneous auricular vagal nerve stimulation (taVNS) on abdominal 
pain and other symptoms in patients with IBS-C. 
Sample size 
N = 42 
Case selection 
criteria 
Inclusion criteria:  
1) age 18–75 years,  
2) willing to sign a written informed consent form,  
3) met the Rome IV diagnostic criteria for IBS-C. 
Exclusion criteria:  
1) had a history of previous abdominal surgery (other than appendectomy), 
2) suffering from carcinoma,  
3) had any organic diseases causing constipation or neurologic diseases 
such as multiple sclerosis, rachischisis, Parkinson’s disease or spinal cord 
injury,  
4) taking antidepressant agents including tricyclic antidepressants and 
selective serotonin reuptake inhibitors,  
5) had a serious concomitant disease of the heart, liver, kidney, or diabetes, 
6) women during pregnancy or lactation,  
7) participating in another trial or enrolled in a trial during the past month, 
8) allergic to surface electrodes. 
Timeline 
1) July 2019 - August 2019: Screen and confirm the clinical diagnosis of 
IBS-C patients, and estimate the sample content 
2) September 2019–July 2020: Patient recruitment，and for the selected 
participants, signed an informed consent form, underwent percutaneous 
auricular vagus nerve stimulation treatment, and collected outcome 
measures 
3) August 2020-October 2020: Data analysis  
Statistical analysis 
The independent sample t-test is used to assess the difference between the 
sham-taVNS and taVNS groups; The paired student’s t-test is applied to 
evaluate the differences before and after the taVNS or sham-taVNS 
treatment. P<0.05 is considered statistically significant. 
 
 
 

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Background 
Irritable bowel syndrome (IBS) is a clinical syndrome characterized by persistent or intermittent 
attacks, abdominal pain, abdominal distension, defecation habits and (or) changes in stool characteristics. 
According to the world-wide population survey, the global prevalence of IBS is about 11.2% (95% CI: 
9.8-12.8) (1), and the prevalence of IBS in China is about 5-10% (2). According to Rome IV diagnostic 
criteria (3), IBS can be divided into four types: constipation type (IBS-C), diarrhea type (IBS-D), mixed 
type (IBS-M) and unclassified type (IBS-U). Among them, IBS-C accounted for about 27% of the total 
prevalence (4). The persistent or intermittent symptoms of patients bring a lot of inconvenience and pain, 
resulting in a significant decline in the quality of life, but also increased the burden of the social health 
system.  
The etiology and pathogenesis of IBS have not been fully elucidated, but many factors are involved, 
including genetic factors, intestinal infection, mucosal immune and inflammatory response, altered 
gastrointestinal motility, visceral hypersensitivity, post infectious reactivity, brain-gut interactions, 
disturbance of intestinal flora, food sensitivity or stress(5-8), among which altered gastrointestinal motility 
and visceral hypersensitivity have been considered to be the main pathophysiological basis. At present, 
various drugs are used for pharmacologic treatment. Laxatives and prokinetics are used for constipation, 
while antispasmodics and antidepressants are prescribed for abdominal pain, which in turn may impair 
gastrointestinal motility and thus could worsen constipation (9, 10). Additionally, such medications can 
only relieve symptoms temporarily, and long-term medication is expensive and easy to relapse after 
withdrawal (11). Accordingly, patients often seek complementary and alternative therapies (12). 
It is well known that the autonomic nervous system is a complex hierarchically controlled system, 
providing a neural link between the brain and the body that integrates the external environment with the 
internal milieu to maintain homeostasis. It is composed of two broadly opposing branches, the 
sympathetic and parasympathetic nervous system, and the vagus nerve is the main neural substrate of 
the parasympathetic nervous system (13). A relative paucity of vagal activity, has been implicated in the 
pathophysiology of a number of disorders including, but not limited to, functional dyspepsia, irritable 
bowel syndrome (IBS), inflammatory bowel disease, and chronic pain syndrome (14, 15). Thus, vagus 
nerve stimulation is of interest as a potential therapeutic intervention. 
Vagus nerve stimulation (VNS), approved by FDA for epilepsy and drug-resistant depression (16), 
has been extended in recent years as a complementary and alternative treatment to treat other diseases, 
including gastrointestinal dysmotility, inflammation and pain (17-19). The classic implantable device 
consists of an electrode, which is wrapped around the left vagus nerve, and an implantable unit, 
positioned below the collarbone and containing the battery and pulse generator. However, despite being 
a minimally invasive procedure, the involvement of surgery, perioperative risks, and potentially 
significant side effects have limited its applicability. 
Transcutaneous vagus nerve stimulation (tVNS) is a noninvasive method that has been developed to 
overcome these limitations. The rationale for using tVNS on the ear is based on anatomical studies that 
suggest that the ear is the only place on the surface of the human body where there is afferent vagus nerve 
distribution (20, 21). Thus, direct stimulation of the afferent nerve fibers on the ear should produce an 
effect similar to classic VNS. In recent years, transcutaneous auricular vagus nerve stimulation (taVNS) 

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has been reported to improve gastrointestinal disorders, including abdominal pain (22), constipation (23) 
and functional dyspepsia (24), but there is no study on ta VNS in the treatment of IBS-C. Based on the 
integrative effects of taVNS on both pain and motility we observed in the animal model of functional 
dyspepsia and patients with abdominal pain-related functional gastrointestinal disorders (22, 24, 25), we 
hypothesized that taVNS might improve symptoms in patient with IBS-C by enhancing vagal efferent 
activity. The aim of this study is to investigate the effects and mechanisms of taVNS on symptoms in 
patients with IBS-C. 
Methods 
Study design and plan 
(1) The patients diagnosed with IBS-C are screened and the sample size is estimated; 
(2) The inclusion and exclusion criteria are selected and informed consent is signed; 
(3) The treatment group is treated with taVNS, while the control group is treated with sham taVNS. The 
blood samples are collected and outcome measures are taken; 
(4) Samples are sent for inspection and the results are statistically analyzed. 
 
Patients 
Inclusion criteria:  
1) age 18–75 years,  
2) willing to sign a written informed consent form,  
3) met the Rome IV diagnostic criteria (26) for IBS-C.  
Exclusion criteria:  
1) had a history of previous abdominal surgery (other than appendectomy),  
2) suffering from carcinoma,  
3) had any organic diseases causing constipation or neurologic diseases such as multiple sclerosis, 
rachischisis, Parkinson’s disease or spinal cord injury,  
4) taking antidepressant agents including tricyclic antidepressants and selective serotonin reuptake 
inhibitors,  
5) had a serious concomitant disease of the heart, liver, kidney, or diabetes,  
6) women during pregnancy or lactation,  
7) participating in another trial or enrolled in a trial during the past month,  
8) allergic to surface electrodes. 
Withdrawal criteria: 
1) The subject or his legal guardian voluntarily requests to withdraw; 
2) Violation of inclusion / exclusion criteria; 
3) Withdraw when other unexplained serious complications occur; 
4) If pregnancy occurs during treatment, withdraw from the study; 
5) For safety reasons, the study sponsor proposed to stop the study; 
6) Subjects whose ethics committee decided to stop the study; 
7) Subjects who are considered unsuitable for further study. 
The reason and date of withdrawal are recorded, and the withdrawal rate is counted at the end of the study. 

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The subjects who withdraw from the study will take appropriate treatment measures according to the 
judgment of the researchers. 
Trial interventions 
Enrolled patients will be randomized to undergo either taVNS or sham-taVNS. The taVNS treatment is 
performed at auricular cymba concha, while Sham-taVNS is performed at a sham point (elbow area).  
Study Design and Protocol 
Enrolled patients are randomly divided into two groups (taVNS and sham-taVNS) with a ratio of 
1:1 according to a computer-generated random digital table. The sample size is calculated by G*power 
analyses based on our preliminary study. One week before the start of the study, patients are asked to 
stop all constipation and IBS medications, including laxatives, prokinetic agents, probiotics, and 
antispasmodics. After one-week run-in period, patients in each group are requested to complete the 
following questionnaires once a week: the visual analog scale (VAS) for abdominal pain, IBS symptom 
severity score (IBS-SSS) for the overall IBS symptoms, IBS quality of life questionnaire (IBS-QOL) 
for patient's quality of life, Bristol Stool Form Scale (BSFS) for the stool type, Self-Rating Anxiety 
Scale (SAS) for anxiety, Self-Rating Depression Scale (SDS) for depression, and the bowel diary for 
the number of complete spontaneous bowel movements per week. Autonomic function is assessed at 
the baseline and after 4 weeks of treatment. by the spectral parameters of heart rate variability (HRV), 
calculated using spectral analysis of R-R intervals in electrocardiogram (ECG). A blood sample is taken 
at 8 a.m. at baseline and after 4 weeks treatment, Serum and plasma are separated and frozen at - 80 ℃. 
The chronic taVNS and sham-taVNS intervention is performed twice a day (8am and 8pm) for half an 
hour each time, lasting for four weeks. During the run-in and treatment periods, only Macrogol 4000 
and pinaverium are permitted for use, when the patient could not tolerate symptoms of constipation and 
abdominal pain. The flowchart is shown in Figure 1, and the study schedule is detailed in Table 1.    
 
  
 
 
 
 
 
 
 
 
 
 
Figure 1. Flowchart of the study design. 
Participant recruitment 
Analysis
Analysed  
Analysed  
Follow up 
Allocation
Lost to follow up  
Lost to follow up 
Group sham-taVNS  
Group taVNS  
Run in for a week 
Baseline assessment 
Exclude 
Randomization (1:1) 
Screening for eligibility  

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Baseline 
Week 1 
Week 2 
Week 3 
Week 4 
Consent 
× 
 
 
 
 
VAS 
× 
× 
× 
× 
× 
IBS-SSS, IBS-QOL 
× 
× 
× 
× 
× 
SAS, SDS, BSFS 
× 
× 
× 
× 
× 
HRV 
× 
 
 
 
× 
Blood 
× 
 
 
 
× 
Table 1. Study schedule. A bowel diary is recorded during the treatment. 
VAS, visual analog scale; IBS-SSS, IBS symptom severity score; IBS-QOL, IBS quality of life 
questionnaire; SAS, Self-rating Anxiety Scale; SDS, Self-rating Depression Scale; BSFS, Bristol stool 
form scale; HRV, heart rate variability. 
Randomization 
Enrolled patients are randomly divided into two groups (taVNS and sham-taVNS) with a ratio of 1:1 
according to a computer-generated random digital table, which contains 21 odd numbers and 21 even 
numbers. Odd numbers represent taVNS, while even numbers represent sham-taVNS, and enter 
corresponding groups according to the sequence of patients. 
Blinding  
The patients are blinded to the type of treatment. 
Serious adverse events (SAEs) 
Pain at the stimulation site and allergy to the electrode are adverse events. Lowering the intensity of 
stimulation can relieve or eliminate pain. If the patient is allergic to the electrode, we will terminate the 
treatment and let the patient withdraw from the study. 
Statistics 
Quantitative variables are reported as means ± standard deviations (SD), while categorical data qualitative 
variables are presented as absolute values and percentages. Categorical data are compared using the chi-
squared test. The independent sample t-test is used to assess the difference between the sham-taVNS and 
taVNS groups; The paired student’s t-test is applied to evaluate the differences before and after the taVNS 
or sham-taVNS treatment. P<0.05 is considered statistically significant. 
Sample size estimation 
G-Power software is used for calculation, and the steps are as follows:  
1. T test, mean difference between two dependent means (two groups) 
2. A priori: compute required sample size, given α, power, and effect size 
3. Tails：One 
4. Effect size:  In the previous study, the number of spontaneous defecation was: 2.3 ± 2.1 (SD) in 
sham stimulation group; 3.7 ± 1.4 (SD) in true stimulation group. Therefore, the effect size 
dz=0.784. 
5.  α=0.05；β=0.2，1-β=0.8； 
Based on the above data, G-Power software calculated total sample size: n = 42 
 
 

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Ethics committee review 
The protocol, written informed consent, and information directly related to the subjects will be submitted 
to the Ethics Committee for written approval before the study can be formally carried out. The researcher 
must submit an annual report of the study to the ethics committee at least annually (if applicable). When 
the study is terminated and / or completed, the researcher must inform the ethics committee in writing; the 
researcher must timely report to the ethics committee all changes in the research work (such as the revision 
of protocol and / or informed consent number), and shall not implement these changes without the 
approval of the ethics committee, unless it is made to eliminate obvious and direct risks to the subjects 
Changes to the contract. When this happens, the ethics committee will be informed. 
Informed consent 
The researcher must provide the subject or his legal representative with the informed consent which is 
easy to understand and approved by the ethics committee, and give the subject or his legal representative 
sufficient time to consider the study. The subject shall not be enrolled until the written informed consent 
is obtained from the subject. All updated versions of informed consent and written information will be 
provided to the subjects during their participation. Informed consent should be kept as an important 
document of clinical trials for future reference. 
Confidentiality measures 
Subject’s medical records (research medical records, examination reports, etc.) will be kept in the hospital, 
and the doctor will record the examination results in outpatient medical records. Researchers, sponsor 
representatives and ethics committee will be allowed to access subject’s medical records. Any public 
report on the results of this study will not disclose subject’s personal identity. We will make every effort 
to protect the privacy of subject’s personal medical data within the scope permitted by law. 
Subject’s medical records will not be used for any purposes other than this study. 
 
Timeline 
1) July 2019 - August 2019: Screen and confirm the clinical diagnosis of IBS-C patients, and estimate 
the sample content 
2) September 2019–July 2020: Patient recruitment, and for the selected participants, signed an informed 
consent form, underwent percutaneous auricular vagus nerve stimulation treatment, and collected the 
outcome measures  
3) August 2020-October 2020: Data analysis  
 
 
 
 
 

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