Transcutaneous Auricular Vagus Nerve Stimulation for Reducing Postoperative Hypoxemia

The Effect of Transcutaneous Auricular Vagus Nerve Stimulation on the Incidence of Postoperative Hypoxemia: A Randomized Controlled Trial

Hypoxemia is a common complication in the post-anesthesia care unit (PACU) and represents one of the most meaningful factors associated with poor patient prognosis. Obese patients have a relatively higher incidence of hypoxemia. This may be partly attributable to their unique physiological characteristics. In addition, surgical trauma triggers a systemic inflammatory response with the release of pro-inflammatory factors such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). These mediators increase pulmonary capillary permeability, induce pulmonary edema, and further impair gas exchange. Surgically-induced stress elevates sympathetic tone and reduces vagal activity, which alters bronchial tone and respiratory rhythm and consequently compromises pulmonary function.Postoperative hypoxemia not only prolongs recovery time and increases the likelihood of ICU admission, but severe episodes may also lead to arrhythmia, myocardial ischemia, long-term cognitive and psychiatric disorders, and even cardiac arrest and death. These outcomes impair postoperative recovery and long-term prognosis, prolong hospital stay, and raise healthcare costs.

Although strategies such as postoperative semi-recumbent positioning and intraoperative protective ventilation have been explored, there are currently no preferred interventions or clear clinical guidelines for the prevention of postoperative hypoxemia.

As a non-invasive technique, transcutaneous auricular vagus nerve stimulation (taVNS) activates the auricular branch of the vagus nerve by stimulating the cymba conchae. Vagal activation suppresses macrophage activity and reduces the release of pro-inflammatory cytokines including TNF-α, IL-1β, IL-6 and IL-18, thereby attenuating pulmonary inflammation and edema and improving oxygenation. Afferent vagal signals project to the nucleus tractus solitarius, modulating the medullary respiratory center, respiratory rate and ventilation efficiency. taVNS is easy to perform, safe, applicable in the perioperative period, and has shown promising effects in regulating inflammatory conditions.

This study aims to investigate whether perioperative taVNS reduces the incidence of hypoxemia in the PACU by attenuating excessive sympathetic activation and mitigating pulmonary and systemic inflammatory responses.

Study Overview

• Status: Not yet recruiting
• Conditions: Hypoxemia
• Intervention / Treatment: Device: Transcutaneous Auricular Vagus Nerve Stimulator

• Study Type: Interventional
• Enrollment (Estimated): 80
• Phase: Not Applicable

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

Age ≥18 years; Scheduled for elective bariatric surgery; Classified as American Society of Anesthesiologists (ASA) physical status I to III; Capable of understanding the study procedures and various assessment scales and able to effectively communicate with the researchers; Willing to participate in the study and provide written informed consent.

Exclusion Criteria:

Patients with severe underlying cardiopulmonary diseases (e.g., acute exacerbation of chronic obstructive pulmonary disease, acute myocardial infarction, NYHA class Ⅳ heart failure); Patients with resting SpO₂ <90% before surgery; Patients with a preoperative heart rate below 50 beats per minute or severe arrhythmia; Patients with lesions of the auricular concha (e.g., inflammation, ulcer, deformity, implant) or vagus nerve dysfunction (e.g., diabetic peripheral neuropathy, vagus nerve injury due to prior neck surgery); Patients with a history of implanted stimulators (e.g., pacemakers, implanted vagus nerve stimulators, deep brain stimulators, spinal cord stimulators), cochlear implants, or metallic implants (excluding dental work); Patients with cognitive dysfunction (MMSE score <20), psychiatric disorders, or unable to cooperate with study procedures; Patients who received vagus nerve stimulation or acupuncture within 1 month before the study; Patients with skin damage or dermatological conditions at the electrical stimulation site; Pregnant or lactating women; Patients requiring emergency surgery; Patients participating in other clinical trials.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Transcutaneous auricular vagus nerve stimulation(taVNS group); Patients in the taVNS group will have a transcutaneous auricular vagus nerve stimulation device with a transparent, non-insulated thin film placed on the cymba conchae of the left ear. TaVNS will be administered on the day of surgery (starting 30 minutes before anesthesia induction and continuing until the end of the surgery, terminating after the removal of the endotracheal tube in the PACU). The stimulation parameters are set as follows: frequency 20 Hz, pulse width 200 μs, 30 seconds on / 30 seconds off, with the current intensity set to the maximum amplitude the patient can tolerate (just below the pain threshold).	Device: Transcutaneous Auricular Vagus Nerve Stimulator; Intervention Timing of Transcutaneous Auricular Vagus Nerve Stimulator: The intervention will begin 30 minutes before anesthesia induction and continue until the end of the surgery, terminating after the removal of the endotracheal tube in the PACU. The stimulation parameters are set as follows: frequency 20 Hz, pulse width 200 μs, 30 seconds on / 30 seconds off, with the current intensity set to the maximum amplitude the patient can tolerate (just below the pain threshold).
No Intervention: Sham transcutaneous auricular vagus nerve stimulation(Sham taVNS group); Patients in the Sham taVNS group will have a transcutaneous auricular vagus nerve stimulation device with a transparent insulating film placed on the cymba conchae of the left ear on the day of surgery. The stimulation parameters, method, and duration will be the same as those in the taVNS group. However, due to the insulating film applied to the stimulation device in the sham group, patients will not actually receive any stimulation.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of Postoperative Hypoxemia in the PACU	Numerous clinical studies and consensus statements define hypoxemia as either peripheral oxygen saturation (SpO₂) less than 90% lasting for more than 10 seconds, or a partial pressure of arterial oxygen to fraction of inspired oxygen (PaO₂/FiO₂) ratio less than 300 mmHg during PACU stay.	Within 30 minutes in the PACU postoperatively

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence and First Onset Time of Moderate Hypoxemia in the PACU	Moderate hypoxemia is defined as SpO₂ less than 85% lasting for more than 10 seconds during PACU stay.The first onset time was defined as the time interval from extubation to the first onset of severe hypoxemia.	Within 30 minutes in the PACU postoperatively
Incidence of Airway Rescue	Airway rescue was defined as the implementation of non-invasive mask ventilation or re-intubation for respiratory support.	Within 30 minutes in the PACU postoperatively
Time to Extubation and PACU Length of Stay	The time interval from the end of surgical procedure to tracheal extubation. The time interval from PACU admission to PACU discharge.	Within 30 minutes in the PACU postoperatively
Postoperative Respiratory Comfort Score	Respiratory comfort was evaluated using a 0-10 numerical rating scale, with higher scores indicating better respiratory comfort and lower scores indicating more severe respiratory discomfort.	Within 30 minutes in the PACU postoperatively
Incidence of Cough, Pulmonary Infection and Atelectasis within 24 hours after surgery		Within the first day post-surgery
Postoperative Visual Analogue Scale (VAS) pain score	VAS scores were assessed at two states: resting state and coughing state, with scores ranging from 0 to 10 points.	Within the first day post-surgery
Total Length of Hospital Stay	The total length of hospital stay refers to the entire duration of the hospitalization from admission to diacharge	Up to 5 weeks postoperatively
Incidence and Severity of Related Adverse Reactions	Adverse reactions included ear skin erythema, local pain, dizziness, nausea, and bradycardia (heart rate < 50 beats per minute). The severity of adverse reactions was graded according to the following standards: Grade 1, mild discomfort without the need for clinical intervention; Grade 2, symptoms relieved after symptomatic treatment; Grade 3, severe adverse reactions requiring termination of study intervention and formal clinical treatment.	Up to 5 weeks postoperatively

Collaborators and Investigators

• Sponsor: Affiliated Hospital of Nantong University

Study record dates

Study Major Dates

• Study Start (Estimated): September 6, 2026
• Primary Completion (Estimated): August 1, 2027
• Study Completion (Estimated): December 1, 2027

Study Registration Dates

• First Submitted: September 14, 2026
• First Submitted That Met QC Criteria: September 14, 2026
• First Posted (Actual): September 18, 2026

Study Record Updates

• Last Update Posted (Actual): September 18, 2026
• Last Update Submitted That Met QC Criteria: September 14, 2026
• Last Verified: September 1, 2026

More Information

Terms related to this study

• Keywords: Hypoxemia; tavns
• Additional Relevant MeSH Terms: Signs and Symptoms, Respiratory; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Hypoxia
• Other Study ID Numbers: 2026-K102-03

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No