An observational study in Ventilator Weaning, Airway Extubation and Respiration, Artificial, sponsored by Seoul National University Hospital. Recruiting at 1 site in South Korea. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-08-18.
Sponsored by Seoul National University Hospital · Observational
The goal of this observational study is to learn if a chest monitor that tracks heart rhythm can help predict whether adults on a breathing machine after surgery will be able to breathe on their own once the breathing tube is removed. It is being done in adults recovering from surgery in the intensive care unit (ICU).
The main questions it aims to answer are:
Can heart rhythm patterns, measured soon after ICU admission and during a breathing test, show whether a patient is likely to breathe well without the machine? Do these patterns change in a helpful way when the breathing tube is removed?
Participants will:
Have soft, sticky patches placed on their chest, similar to those used for a regular heart monitor Have their heart rhythm recorded for 5 minutes at four times: soon after ICU admission, before a breathing test, during the breathing test, and right after the breathing tube is removed Continue to receive their usual ICU care; doctors will not see the monitor's readings, so these readings will not affect any treatment decisions
\<Background and Rationale>
Delayed liberation from invasive mechanical ventilation after surgery is associated with increased risk of ventilator-associated pneumonia, prolonged sedation and analgesic exposure, ICU-acquired weakness, delirium, and longer ICU and hospital stays. Identifying patients at risk of extubation failure before or during a spontaneous breathing trial (SBT) could allow clinicians to better time weaning attempts and reduce these complications.
The autonomic nervous system plays a broader physiological role than heart rate control alone, contributing to respiratory muscle regulation, the cholinergic anti-inflammatory pathway, and the stress response. Heart rate variability (HRV) is a validated, non-invasive marker of autonomic function, and reduced HRV has been associated with multiorgan dysfunction and mortality in critically ill patients. The weaning process, particularly the SBT, imposes substantial autonomic and cardiorespiratory stress through abrupt changes in intrathoracic pressure, preload and afterload, and oxygen demand, resembling a physiological stress test.
Several studies have examined HRV around the time of SBT and its association with weaning or extubation outcomes, generally showing that reduced total power or altered low-frequency/high-frequency ratios are associated with SBT failure. However, prior studies have relied on offline, retrospective HRV processing methods that are not readily applicable at the bedside, and none have evaluated HRV parameters derived from a real-time, point-of-care Analgesia Nociception Index (ANI) monitor in relation to extubation outcomes. In addition, no prior study has evaluated whether autonomic function measured at ICU admission, prior to any weaning attempt, predicts subsequent extubation success, nor has this question been examined specifically in postoperative surgical ICU patients.
The ANI monitor (MDoloris Medical Systems, France) is a commercially available, non-invasive device that derives HRV-based indices from surface ECG in real time, producing an instantaneous index (ANIi), a smoothed mean index (ANIm), and a signal quality/magnitude index (Energy, based on SDNN). ANI monitoring is an established, nationally approved technology for intraoperative nociception monitoring in Korea since 2021, but its use as a physiologic prognostic tool in the ICU, specifically for predicting extubation outcomes, remains unexplored.
\<Study Design>
This is a single-center, prospective, observational pilot cohort study conducted in the surgical ICU of a tertiary academic hospital. As a pilot study, no formal sample size calculation was performed; findings are intended to generate preliminary effect estimates and inform the sample size calculation for a subsequent multicenter study.
To minimize confounding from sedative agents with differing autonomic effects, enrollment is restricted to patients sedated with dexmedetomidine as the primary agent, since dexmedetomidine acts directly on alpha-2 receptors to suppress sympathetic activity, in contrast to GABA-mediated agents such as propofol or benzodiazepines, which have been shown to affect HRV parameters differently.
\<Measurement Procedures>
ANI-derived HRV parameters (ANIi, ANIm, Energy) are measured non-invasively via chest-surface ECG patches for 5 minutes at each of four standardized time points: (1) baseline, on the day of ICU admission after confirming stable sedation (RASS -2 to -5 maintained for at least 30 minutes); (2) immediately before the SBT, at transition to pressure support ventilation, using the pre-existing ventilator settings; (3) during the SBT, 10-15 minutes after transition to pressure support ventilation (recommended settings: pressure support 8 cmH2O, PEEP 5 cmH2O, adjustable at clinician discretion, with actual settings recorded); and (4) immediately after extubation, regardless of subsequent success or failure. If ICU admission and extubation occur on the same day, baseline and pre-SBT measurements are obtained separately.
The ANI monitor display is shielded from the treating clinical team throughout the study period so that monitoring values do not influence clinical decision-making. The decision to proceed with SBT and extubation remains entirely at the discretion of the treating physicians and follows standardized institutional SBT initiation/termination criteria (based on oxygen saturation, respiratory rate, heart rate change from baseline, blood pressure, work of breathing, and mental status), which are recorded for use as covariates but do not constitute a study intervention.
Only the SBT and extubation attempt performed on the initial intubation episode (i.e., the final weaning attempt prior to the first extubation) are included in the primary analysis; SBTs or extubation attempts occurring after reintubation are excluded from primary analysis.
\<Data Collection>
In addition to the ANI parameters, the following data are collected via electronic medical record review: demographic and baseline characteristics (age, sex, height, weight, surgery type, elective/emergency status, comorbidities); severity scores at ICU admission (SOFA, APACHE II); sedation and analgesia data (agent, dose, RASS, use of patient-controlled analgesia); hemodynamic and ventilatory parameters (vasopressor use, ventilator settings including FiO2, PEEP, respiratory rate, tidal volume, and actual SBT settings); inflammatory and hematologic laboratory values (CRP, procalcitonin, lactate, complete blood count); and clinical outcomes including length of ICU/hospital stay, mortality, and delirium status (CAM-ICU). No additional invasive procedures, blood draws, or interventions beyond standard ICU care are performed for research purposes; ANI monitoring uses only chest-surface ECG patches, similar to routine cardiac monitoring.
\<Statistical Analysis Plan>
Continuous variables will be assessed for normality using the Shapiro-Wilk test and summarized as mean (SD) or median (IQR) accordingly; categorical variables will be summarized as frequencies and percentages, with Fisher's exact test applied when expected cell counts are below 5.
Associations between each ANI parameter at each time point and the primary outcome will be assessed using univariable logistic regression, reported as odds ratios with 95% confidence intervals. A multivariable model adjusting for SOFA score and cumulative opioid dose (fentanyl equivalents) will be performed; these two covariates were selected a priori based on their established association with weaning outcomes in the literature, with the number of covariates deliberately limited given the small pilot sample size, following the events-per-variable principle to avoid model overfitting.
Because three time points (baseline, pre-SBT, and during-SBT ANI) are each tested as primary predictors, this multiplicity is explicitly acknowledged as exploratory analysis, and formal multiplicity correction (e.g., Bonferroni) is applied exploratorily rather than as a primary inferential adjustment, consistent with the pilot nature of the study. For parameters showing a significant association, receiver operating characteristic curve analysis will be performed to explore the area under the curve and candidate cut-off values.
Secondary analyses include univariable logistic regression for the association between post-extubation ANI and 48-hour reintubation, and for the association between the within-day change in ANI (pre-SBT to during-SBT, ΔANI) and successful extubation. Length of stay will be analyzed using Spearman correlation after assessing normality. All statistical tests are two-sided, with significance defined as p \< 0.05.
Statistical analysis will be performed after completion of enrollment for the pilot cohort (target: up to approximately 50 participants over a 6-month enrollment period), with a total study duration of 12 months from IRB approval, including follow-up medical record review.
1,780 studies on the registry are indexed under Critical Illness; 442 are open to participants now.
This study's planned enrollment of 50 is below the median of 140 across 814 observational studies indexed under Critical Illness.
Browse Critical Illness studies →Seoul National University Hospital is the lead sponsor of 1,900 studies on the registry; 274 are open to participants now.
Of its 12 completed or terminated interventional studies of FDA-regulated products, 2 (17%) have results posted.
Counted across the registry records on this site, refreshed daily.
Participants are drawn from adult patients admitted to the surgical intensive care unit (ICU) of Seoul Metropolitan Government Seoul National University Boramae Medical Center, a public academic hospital in Seoul, South Korea, following surgery. The surgical ICU cares for postoperative patients across multiple surgical specialties, including general surgery, thoracic and cardiovascular surgery, and other surgical disciplines requiring postoperative critical care. Eligible participants are identified from among those requiring invasive mechanical ventilation after surgery and sedated according to standard ICU sedation practice at this institution.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
proportion of participants with successful extubation
A participant's breathing tube is removed (extubated) after a period of mechanical ventilation, following a trial in which the ventilator support is reduced to see if the participant can breathe adequately on their own (a spontaneous breathing trial). Extubation is considered successful if the participant does not need the breathing tube reinserted within 48 hours. If a participant dies within this 48-hour window without having the breathing tube reinserted, this is not counted as a failed extubation and is recorded as a separate outcome. This outcome will be analyzed in relation to heart rate variability measurements (an indicator of autonomic nervous system activity, obtained non-invasively from a chest monitor) taken at the time of intensive care unit admission, before the breathing trial, and during the breathing trial.
Time frame: Within 48 hours after extubation
Proportion of Participants with Reintubation Following Post-Extubation ANI Measurement
Reintubation is defined as reinsertion of a breathing tube within 48 hours after extubation. This outcome will be analyzed in relation to heart rate variability values measured by a chest monitor immediately after extubation, to explore whether values recorded right after the breathing tube is removed are associated with the need to reinsert it.
Time frame: Within 48 hours after extubation
Proportion of Participants with Successful Extubation, by Change in Heart Rate Variability During the Breathing Trial
The change in heart rate variability value (a measure of autonomic nervous system activity obtained from a chest monitor) between the measurement taken just before the breathing trial and the measurement taken during the breathing trial will be calculated for each participant. Successful extubation is defined as no reinsertion of the breathing tube within 48 hours after extubation. This outcome will be analyzed according to the magnitude of change in heart rate variability
Time frame: From immediately before the breathing trial to 48 hours after extubation
Length of Stay in the Intensive Care Unit and Hospital
Length of stay is defined as the number of days from intensive care unit (ICU) admission to ICU discharge, and from hospital admission to hospital discharge, respectively.
Time frame: From ICU admission until ICU discharge or hospital discharge, up to 28 days
Proportion of Participants who Died in the Intensive Care Unit, in the Hospital, or Within 28 Days
Death occurring during the intensive care unit (ICU) stay, during the hospital stay, and within 28 days of study enrollment will each be recorded separately as three distinct measures of mortality.
Time frame: From ICU admission up to 28 days, or until hospital discharge, whichever occurs first
Proportion of Participants with Delirium as Assessed by CAM-ICU
Delirium was assessed using the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU), a validated bedside screening tool administered by trained staff. A participant is considered positive for delirium if they show both (1) an acute change or fluctuation in mental status and (2) inattention, together with either (3a) disorganized thinking or (3b) an altered level of consciousness. This tool produces a binary result (delirium present or absent) rather than a numeric score.
Time frame: Daily during the intensive care unit stay, up to 28 days
Plan to share: Yes — All individual participant data (IPD) collected during this study that underlie the results reported in future publications will be shared, including de-identified demographic, clinical, laboratory, and Analgesia Nociception Index (ANI)-derived heart rate variability measurements. Data will be shared, after de-identification, beginning after publication of the primary study results and ending 5 years after study completion, consistent with the data retention period specified in the informed consent document. Sharing will be conducted in accordance with Article 18 of the Korean Bioethics and Safety Act and institutional review board approval, upon reasonable request to the corresponding author, for purposes such as independent verification of results or meta-analysis.
Supporting information: Study protocol, Statistical analysis plan, Informed consent form, Clinical study report
Time frame: Start Date: Beginning 3 months after the publication of results End Date: Ending 5 years after study completion
Access criteria: Researchers seeking access to individual participant data (IPD) must submit a written request to the corresponding author, including a research proposal that describes the specific objectives, planned analyses, and statistical methods to be used. Requests will be reviewed by the study's principal investigator to confirm that the proposed use is scientifically sound and consistent with the objectives outlined in the original study protocol and the scope of participant consent. Data will be shared only after execution of a data sharing agreement that specifies conditions for data use, including restrictions on re-identification attempts, requirements for secure data storage, and prohibition of further redistribution to third parties without additional authorization. Approval from the Institutional Review Board of Seoul Metropolitan Government Boramae Medical Center may be required prior to release, depending on the nature of the request. All shared data will be de-identified in accordanc
Started Aug 2026 (actual). Primary completion is estimated for Feb 2027, 6 months after the start.
Of 439 non-industry observational studies under Critical Illness, half reached primary completion within 23 months of starting (the median), counting those still running; a quarter within 12 and three quarters within 45. This study's planned 6 months is below that.
Counting every sponsor, half of 442 studies reached it within 23 months; a quarter within 12 and three quarters within 46.
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