Effects of Electroacupuncture at NP82 and SP15 on Bowel Motility in Healthy Subjects

Background and Rationale:

Bowel motility is a fundamental physiological function regulated by the autonomic nervous system. This study explores the potential of electroacupuncture (EA) to modulate this activity using a unique acupoint combination: Dai Hoanh (SP15), a classic point known for regulating the Spleen and Stomach, and Thong Tien (NP82), a newly proposed "extra point" specifically indicated for treating paralysis-related constipation in traditional literature. The study aims to provide the first modern scientific evidence for the effectiveness of NP82 in stimulating bowel motility.

Methodology:

The study follows a before-and-after intervention design involving 30 healthy volunteers. To ensure objective measurement, bowel sounds are recorded using the 3M™ Littmann® CORE Digital Stethoscope, which amplifies sounds and allows for computerized analysis, overcoming the subjectivity of traditional auscultation.

The procedure consists of three phases:

1. Baseline Phase: Continuous 30-minute recording of bowel sounds to establish a physiological reference.
2. Intervention Phase: Simultaneous 20-minute recording during EA. Sterile needles (0.30×40mm) are inserted into NP82 and SP15 points until "De Qi" sensation is achieved. Stimulation utilizes a dense-disperse wave at a 10 Hz frequency, with intensity adjusted (0.1-1 mA) based on participant tolerance.
3. Post-intervention Phase: Continuous 30-minute recording after needle removal to evaluate sustained effects.

Blinded Outcome Assessment Note:

Although the clinical phase of this trial is formally registered as open-label (None/Open) due to its single-arm pre-post interventional design, a rigorous blinded outcome assessment was implemented during data analysis. The raw digital acoustic recordings were completely de-identified, randomized, and assigned arbitrary codes. The independent clinical experts responsible for manual bowel sound annotation and validation were fully masked to the participants' identities and the chronological sequence of the recording phases (baseline, active electroacupuncture, or post-intervention).

Data Analysis:

Automated signal preprocessing, ARMA-based event segmentation, and acoustic parameter extraction will be executed using Python programming software (version 3.10 or later) utilizing the SciPy and NumPy packages. All subsequent statistical analyses will be performed using R statistical software (version 4.3.0 or later; R Core Team, Vienna, Austria). Since acoustic bowel motility parameters do not exhibit a normal distribution (evaluated via the Shapiro-Wilk test), non-parametric paired Wilcoxon signed-rank tests will be utilized for all pairwise comparisons across the three experimental phases (baseline vs. active intervention, baseline vs. post-intervention, and active intervention vs. post-intervention). Continuous variables will be reported as Medians with Interquartile Ranges (IQR). A p-value of < 0.05 will establish the threshold for statistical significance for all tests

• Electroacupuncture at NP82 (Tongbian) and SP15 (Daheng) (Procedure), also known as EA at NP82 and SP15 points: The intervention is performed by practitioners with at least 3 years of experience. Sterile acupuncture needles (0.30×40mm) are inserted vertically into the Tongbian (NP82 - located 3 cun lateral to the umbilicus) and Daheng (SP15 - located 4 cun lateral to the umbilicus) acupoints. Insertion depth ranges from 20 to 65 mm depending on the participant's body type, aiming to achieve the "De Qi" sensation (aching, heaviness, and tension). Electrical stimulation is applied using a Hwato SDZ-III device with a dense-disperse wave at a frequency of 10 Hz for 20 minutes. The current intensity is adjusted (0.1-1 mA) until a mild muscle vibration is visible without causing pain to the participant.

Primary outcomes

• Bowel Sound Interval (SSI) [Continuous recording across three phases: Baseline (30 minutes before intervention), During Intervention (20 minutes), and Post-intervention (30 minutes).]: SSI is the time interval between the end of one bowel sound event and the start of the next. Bowel sounds are recorded and quantified using the 3M™ Littmann® CORE Digital Stethoscope and analyzed with Stata 17.0 software to determine changes in bowel motility.

Secondary outcomes

• Minimum SSI Ratio (SSIR) [The total study duration is 80 minutes, consisting of: (1) Baseline phase: 30 minutes before intervention; (2) Intervention phase: 20 minutes during electroacupuncture; and (3) Post-intervention phase: 30 minutes after needle removal.]: SSIR is calculated as the ratio of the minimum Bowel Sound Interval (SSI) during or after the intervention (Ba) to the minimum SSI before the intervention (Bb). SSI values are derived from digital recordings of bowel sounds captured by a 3M™ Littmann® CORE Digital Stethoscope. The analysis focuses on 10-minute windows within each phase to determine the maximum increase in bowel motility compared to the baseline.
• Bowel Sound Duration Ratio (BSDR) [Continuous recording across three phases: Baseline (30 minutes), Active Electroacupuncture (20 minutes), and Post-intervention (30 minutes)]: Defined as the percentage of the total analytical window duration occupied by active bowel sound events. To account for the unequal durations of the study phases, this metric is calculated using a phase-dependent denominator T as follows: BSDR (%) = (Total BS Duration / T) * 100%, where T = 30 minutes for the baseline and post-intervention phases, and T = 20 minutes for the active electroacupuncture phase
• Bowel Sound Frequency [Continuous recording across three phases: Baseline (30 minutes), Active Electroacupuncture (20 minutes), and Post-intervention (30 minutes)]: Defined as the number of independent bowel sound events detected per minute within each study phase. This metric is computed as the total count of bowel sound events divided by the phase-specific window duration T (where T = 30 minutes for the baseline and post-intervention phases, and T = 20 minutes for the active electroacupuncture phase)

Sex: All, ages: 18 Years to 30 Years, accepts healthy volunteers

Inclusion Criteria:

* Healthy volunteers aged 18 years and older.
* No symptoms related to constipation after comprehensive evaluation based on Rome IV criteria.
* No gastrointestinal symptoms (abdominal pain, diarrhea, blood in stool, constipation, or bloating) in the 4 weeks prior to study participation.
* No use of medications that promote or inhibit bowel motility in the 4 weeks prior to participation (including prokinetics, laxatives, antispasmodics, or opioids).
* Fasting for at least 4 hours before the study session.
* No mental or intellectual disorders; capable of understanding the acupuncture and assessment procedures.
* Willingness to participate and signed informed consent form.

Exclusion Criteria:

* Participants with severe medical conditions (heart, brain, liver, kidney, hematological system, infectious diseases, cancer, or psychiatric disorders).
* Metabolic or functional disorders such as irritable bowel syndrome (IBS), thyroid dysfunction, or glucose/lipid metabolism disorders.
* Use of bowel motility-altering medications within the 4 weeks prior to participation.
* Participation in other clinical trials within the last 2 months.
* Received acupuncture treatment within the last month.
* Skin ulcers, abscesses, or infections at the acupuncture sites.
* Known metal allergy or severe needle phobia.

• Results publication: Wang G, Wang M, Liu H, Zhao S, Liu L, Wang W. Changes in bowel sounds of inpatients undergoing general anesthesia. Biomed Eng Online. 2020 Jul 30;19(1):60. doi: 10.1186/s12938-020-00805-z. PMID 32731903
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• Results publication: Ong SS, Tang T, Xu L, Xu C, Li Q, Deng X, Shen P, Chen Y, Song Y, Lu H, Fang L. Research on the mechanism of core acupoints in electroacupuncture for functional constipation based on data mining and network acupuncture. Front Med (Lausanne). 2024 Dec 11;11:1482066. doi: 10.3389/fmed.2024.1482066. eCollection 2024. PMID 39722820
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• Results publication: Abbasi P, Mojalli M, Kianmehr M, Zamani S. Effect of acupressure on constipation in patients undergoing hemodialysis: A randomized double-blind controlled clinical trial. Avicenna J Phytomed. 2019 Jan-Feb;9(1):84-91. PMID 30788281
• Results publication: Zhao X, Liu L, Diao Y, Ma C. Effectiveness of abdominal electroacupuncture therapy for poststroke constipation: a meta-analysis. Front Neurol. 2024 Nov 22;15:1480681. doi: 10.3389/fneur.2024.1480681. eCollection 2024. PMID 39650243

• Minh Quan Le Hoang, MSc, MD, Principal investigator, University of Medicine and Pharmacy at Ho Chi Minh City