Measurement of Airway Opening Index During Out-of-hospital Cardiac Arrest: The Lazarus AOI Trial. (Lazarus-AOI)

Out-of-hospital cardiac arrest (OHCA) is a leading cause of death worldwide. Despite constantly improving resuscitation techniques, the chances of survival remain limited. During cardiopulmonary resuscitation (CPR), a closure of the airway may occur, impeding ventilation. This phenomenon also complicates the interpretation of the end-tidal CO2 (ETCO2) in the capnogram. The extent to which airway closure occurs is quantified by the Airway Opening Index (AOI). This can be calculated from the capnogram and is seen as a measure of the quality of CPR applied as well as a possible indicator to predict the outcome of CPR.

In this study, we analyse capnogram data from approximately 150 cases, collected during interventions for OHCA and logged in the Lazarus database (UZ Gent and AZORG) to answer three research questions below:

1. What is the prevalence of AOI during CPR?
2. Is there a correlation between AOI and return of spontaneous circulation (ROSC)?
3. Does the application of positive end-expiratory pressure (PEEP) affect the AOI and ROSC?

A mathematical model for calculating AOI, based on a method from previous work by Bandhari et al. [1] will be developed. Using this model, the AOI will be calculated from the individual capnograms for all cases in the Lazarus database.

In addition, a multivariable regression model will be used to analyse whether AOI can be used to predict ROSC. Corrections will be made for relevant confounders such as age, gender, witnessed arrest and rhythm pattern.

Finally, it is investigated whether PEEP has a positive influence on AOI. This study aims to contribute to better insights into airway dynamics during CPR and the optimization of ventilation in OHCA.

Study Overview

• Status: Recruiting
• Conditions: Cardiac Arrest (CA); Out-of-hospital Cardiac Arrest (OHCA); Resuscitated Sudden Cardiac Death

Detailed Description

This study is a retrospective observational cohort study based on capnography data from out-of-hospital cardiac arrest cases registered in the Lazarus database.

• Study Type: Observational
• Enrollment (Estimated): 150

Contacts and Locations

• Study Contact: Name: Said Hachimi Idrissi, MD, PhD; Phone Number: 0032 9 332 50 24; Email: SAID.HACHIMIIDRISSI@ugent.be
• Study Contact Backup: Name: Thomas Tackaert, MD; Email: thomas.tackaert@ugent.be

Study Locations

• Belgium
  • East-Flanders
    • Ghent, East-Flanders, Belgium, B9000
      • Recruiting
      • Ghent University Hospital
      • Contact: Said Hachimi Idrissi, MD, PhD; Phone Number: 0032 9 332 50 24; Email: SAID.HACHIMIIDRISSI@ugent.be

Participation Criteria

Eligibility Criteria

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

• Sampling Method: Non-Probability Sample

Study Population

This retrospective observational cohort study included adult patients who suffered an out-of-hospital cardiac arrest (OHCA) and were treated by the Mobile Emergency Team (MET) of Ghent University Hospital. All cases were registered in the Lazarus database, which prospectively collects prehospital CPR data including continuous capnography recordings.

Description

Inclusion Criteria:

• Adult (over 18 years old) patients with out-of-hospital cardiac arrest.
• Patients undergoing cardiopulmonary resuscitation (CPR).
• Patients who were intubated and had available capnogram recordings immediately after intubation.

Exclusion Criteria:

• Patients that were not intubated
• Patients that did not receive CPR following intubation
• Cases with a technical challenge with the ETCO₂ measurement (i.e., issues with waveform data of the capnogram.

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort
ROSC; Patients with return-of-spontaneous circulation during initial resuscitation.
non-ROSC; Patients without return-of-spontaneous circulation during initial resuscitation.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
ROSC	Return-of-spontaneous circulation during initial resuscitation.	Initial resuscitation (first day)

Collaborators and Investigators

• Sponsor: University Hospital, Ghent

Study record dates

Study Major Dates

• Study Start (Actual): October 1, 2022
• Primary Completion (Estimated): September 30, 2026
• Study Completion (Estimated): January 1, 2027

Study Registration Dates

• First Submitted: November 14, 2025
• First Submitted That Met QC Criteria: February 23, 2026
• First Posted (Actual): February 27, 2026

Study Record Updates

• Last Update Posted (Actual): February 27, 2026
• Last Update Submitted That Met QC Criteria: February 23, 2026
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: capnography; airway closure
• Additional Relevant MeSH Terms: Cardiovascular Diseases; Heart Diseases; Heart Arrest; Out-of-Hospital Cardiac Arrest
• Other Study ID Numbers: ONZ-2025-0418

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

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