Comparison of Acoustic Variability Index (AVI) and Pulse Pressure Variation (PPV) for Predicting Fluid Responsiveness in Mechanically Ventilated Patients

A Prospective, Single-Center, Single-Arm, Paired-Comparison, Open-Label, Non-Inferiority Confirmatory Trial to Evaluate the Efficacy and Safety of ResQ by Comparing Fluid Responsiveness Prediction Performance of the Acoustic Variability Index (AVI) Versus Pulse Pressure Variation (PPV) in Mechanically Ventilated Patients

The goal of this clinical trial is to learn if a new medical device called ResQ works to predict fluid needs in adults undergoing surgery under general anesthesia. The main questions it aims to answer are:

• Can the Acoustic Variability Index (AVI) measured by ResQ predict if a participant needs more fluids as accurately as the standard arterial blood pressure-based method (PPV)?
• Is the ResQ device safe to use during surgery? Researchers will compare the new method (AVI) to the standard method (PPV) to see if ResQ provides reliable information for managing patient fluids.

Participants will:

• Undergo their planned surgery as scheduled.
• Have a soft probe placed in the esophagus to monitor heart and lung sounds.
• Receive a set amount of intravenous (IV) fluid as part of their regular surgery care.
• Have their heart function checked before and after the fluids are given.

Study Overview

• Status: Recruiting
• Conditions: Anesthesia, General; Hemodynamic Monitoring; Fluid Responsiveness Predictability
• Intervention / Treatment: Device: Biological Signal Processing Device for Acoustic Variability Index; Device: Patient monitor for pulse pressure variation; Device: Hemodynamic monitor for cardiac Output and stroke volume variation; Device: Patient monitor for pleth variability index; Device: Anesthesia monitoring system for respiratory rate

• Study Type: Observational
• Enrollment (Estimated): 122

Contacts and Locations

• Study Contact: Name: Hye-Mee Kwon, MD, PhD; Phone Number: +82-3010-1438; Email: hyemee.kwon@amc.seoul.kr

Study Locations

• South Korea
  • Seoul
    • Seoul, Seoul, South Korea, 05505
      • Recruiting
      • Asan Medical Center
      • Contact: Hye-Mee Kwon, MD, PhD; Phone Number: +82-1688-7575; Email: hyemee.kwon@amc.seoul.kr
      • Principal Investigator: Hye-Mee Kwon, MD, PhD

Participation Criteria

Eligibility Criteria

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

• Sampling Method: Non-Probability Sample

Study Population

The study population consists of adult patients at Asan Medical Center in Seoul, South Korea. Participants will be recruited from the patients scheduled to undergo elective major surgeries involving organs in the abdominal, retroperitoneal, or pelvic cavities (such as hepatobiliary, pancreatic, intestinal, renal, or uterine procedures). These patients will be receiving general anesthesia and mechanical ventilation and are expected to require continuous intraoperative hemodynamic monitoring as part of their standard surgical care.

Description

Inclusion Criteria:

To participate in this study, individuals must meet all of the following criteria:

• Adults aged 19 years or older.
• If female, not pregnant or breastfeeding.
• Scheduled for a planned surgery of major organs in the abdominal, retroperitoneal, or pelvic cavities (e.g., hepatobiliary and pancreatic, small intestine, large intestine, kidney, uterus) under general anesthesia with mechanical ventilation
• Classified as American Society of Anesthesiologists (ASA) Class I, II, or III. (Note: Excluded regardless of class if any exclusion criteria are met)
• Scheduled to receive mechanical ventilation in a volume-controlled or pressure-controlled mode in the operating room or intensive care unit, with an anticipated tidal volume of 6-8 mL/kg (Ideal Body Weight), respiratory rate of 8-14 breaths/min, and PEEP of 0-5 cmH2O
• Scheduled for hemodynamic monitoring to measure the comparison indices during surgery
• Able to understand the study's purpose and procedures and communicate clearly with the investigator and research staff
• Voluntarily signed the written informed consent form before participating in the study

Exclusion Criteria:

Individuals meeting any of the following criteria will be excluded from participation:

• Undergoing emergency or unplanned surgery
• Anticipated to have difficulty with the application of general anesthesia or mechanical ventilation
• Anticipated to experience massive bleeding of 1 L or more during surgery.
• Undergoing a reoperation due to the same underlying disease
• History of severe esophageal damage (e.g., esophageal varices or stricture) that makes inserting the probe difficult
• Inability to have an arterial catheter inserted, making the measurement of Stroke Volume Variation (SVV) and Pulse Pressure Variation (PPV) difficult
• Condition where a fluid challenge is contraindicated or considered high risk (e.g., clinical signs of fluid overload, pulmonary congestion, or pulmonary edema; acute exacerbation of heart failure or renal failure; or a hemodynamically unstable state)
• Body Mass Index (BMI) greater than 30 kg/m²
• Uncontrolled coagulopathy prior to surgery (e.g., Platelet count < 100,000/μL or INR > 2)
• Arrhythmias, such as atrial fibrillation/flutter or premature atrial/ventricular contractions (>2 per 10 seconds), that make it difficult for the variability index to operate accurately
• Other cardiovascular history that makes accurate cardiac output measurement impossible (e.g., severe valvular disease, history of intracardiac shunt surgery, or structural heart surgery)
• Pregnant or lactating women
• Any other condition deemed unsuitable for study participation by the investigator

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Intervention / Treatment

Mechanically Ventilated Surgical Patients (Paired-Comparison); Adult patients (aged 19 years or older) scheduled for elective major abdominal, retroperitoneal, or pelvic surgery under general anesthesia and mechanical ventilation. In this single-arm, within-subject paired-comparison cohort, each participant undergoes real-time monitoring of hemodynamic indices-specifically the Acoustic Variability Index (AVI) and Pulse Pressure Variation (PPV)-both before and after a standardized 500 mL fluid challenge. This design allows for a direct comparison of the two indices within the same physiological state for each participant.

Device: Biological Signal Processing Device for Acoustic Variability Index; A biosignal processing device that measures AVI and RR continuously in real-time. It analyzes heart and lung sounds collected via a general-purpose internal probe inserted into the patient's esophagus.; Other Names: SH-ResQ-01; ResQ; Device: Patient monitor for pulse pressure variation; A standard multi-parameter patient monitor used to measure the reference hemodynamic index, Pulse Pressure Variation (PPV), via an arterial catheter; Other Names: GE CARESCAPE Monitor B850; Device: Hemodynamic monitor for cardiac Output and stroke volume variation; A specialized hemodynamic monitoring system used to measure the reference standard for fluid responsiveness: Cardiac Output (CO) and Stroke Volume Variation (SVV); Other Names: Edwards HemoSphere Monitor; Device: Patient monitor for pleth variability index; A patient monitoring system used to measure the Pleth Variability Index (PVI) via a non-invasive sensor attached to the finger or toe; Other Names: Masimo Root Monitor; Device: Anesthesia monitoring system for respiratory rate; An anesthesia delivery and monitoring system used to provide the reference Respiratory Rate (RR) measurement based on end-tidal CO2 (EtCO2) waveforms during general anesthesia; Other Names: GE Carestation 750

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Comparison of Area Under the Receiver Operating Characteristic (ROC) Curve (AUC) between AVI and PPV for Predicting Fluid Responsiveness (Non-inferiority)	Assessed by calculating and comparing the Area Under the Curve (AUC) of the Receiver Operating Characteristic (ROC) curve for both indices to predict fluid responsiveness. The non-inferiority of AVI compared to PPV will be evaluated. Fluid responsiveness is defined as a Cardiac Output (CO) increase of 10% or more following a 500 mL fluid challenge.	Baseline (assessed continuously for 3 minutes before fluid challenge) and 3 minutes after a 500 mL fluid challenge

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Concordance of Respiratory Rate (RR) between ResQ and Carestation 750	Assessed by evaluating the agreement of respiratory rate (RR) measurements between the ResQ device and the reference anesthesia workstation (Carestation 750).	Baseline (assessed continuously for 3 minutes before fluid challenge) and 3 minutes after a 500 mL fluid challenge.
Comparison of Area Under the Receiver Operating Characteristic (ROC) Curve (AUC) between AVI and PVI for Predicting Fluid Responsiveness	Assessed by calculating and comparing the Area Under the Curve (AUC) of the Receiver Operating Characteristic (ROC) curve for both indices to predict fluid responsiveness. Fluid responsiveness is defined as a Cardiac Output (CO) increase of 10% or more following a 500 mL fluid challenge.	Baseline (assessed continuously for 3 minutes before fluid challenge) and 3 minutes after a 500 mL fluid challenge.
Comparison of Area Under the Receiver Operating Characteristic (ROC) Curve (AUC) between AVI and SVV for Predicting Fluid Responsiveness	Assessed by calculating and comparing the Area Under the Curve (AUC) of the Receiver Operating Characteristic (ROC) curve for both indices to predict fluid responsiveness. Fluid responsiveness is defined as a Cardiac Output (CO) increase of 10% or more following a 500 mL fluid challenge.	Baseline (assessed continuously for 3 minutes before fluid challenge) and 3 minutes after a 500 mL fluid challenge
Diagnostic performance of AVI for fluid responsiveness (Sensitivity, Specificity, Positive Predictive Value, Negative Predictive Value)	Assessed by calculating sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) based on the optimal cut-off value determined by ROC curve analysis to evaluate the diagnostic performance of AVI.	Baseline (assessed continuously for 3 minutes before fluid challenge) and 3 minutes after a 500 mL fluid challenge

Collaborators and Investigators

• Sponsor: Signal House Co., Ltd.
• Collaborators: Ministry of SMEs and Startups, Korea
• Investigators: Principal Investigator: Hye-Mee Kwon, MD, PhD, Asan Medical Center

Study record dates

Study Major Dates

• Study Start (Actual): April 13, 2026
• Primary Completion (Estimated): October 1, 2026
• Study Completion (Estimated): December 1, 2026

Study Registration Dates

• First Submitted: March 24, 2026
• First Submitted That Met QC Criteria: March 31, 2026
• First Posted (Actual): April 8, 2026

Study Record Updates

• Last Update Posted (Actual): April 29, 2026
• Last Update Submitted That Met QC Criteria: April 23, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Fluid Responsiveness; Hemodynamic Monitoring
• Additional Relevant MeSH Terms: Diagnostic Techniques and Procedures; Diagnosis; Circulatory and Respiratory Physiological Phenomena; Respiration; Respiratory Physiological Phenomena; Diagnostic Techniques, Cardiovascular; Physical Examination; Heart Function Tests; Vital Signs; Hemodynamics; Cardiovascular Physiological Phenomena; Respiratory Rate; Hemodynamic Monitoring; Monitoring, Physiologic; Cardiac Output
• Other Study ID Numbers: SI_RESQ_02

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED
• IPD Plan Description: A decision on whether to share Individual Participant Data (IPD) has not yet been made. The sponsor and investigators are currently evaluating the data sharing policy, and this record will be updated once a formal decision is reached.

Drug and device information, study documents

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