Prospective Observational Study of Exhaled Carbon MonoxideTrajectories and Outcomes in ICU Patients
For patients and families
In plain language
An automatic summary of structured registry data. It is an orientation aid, not a substitute for the official protocol or a physician assessment.
- What is being studied
- This is an observational study: the protocol does not assign a study treatment.
- Who it may be relevant to
- Registry conditions: Critical Illness； Intensive Care Unit Patients. Basic parameters: from 18 years · All.
- What needs checking
- Age, condition and sex are only basic indicators. Prior treatment, laboratory values and other mandatory requirements appear in the eligibility criteria below.
- Where it takes place
- Center list to be confirmed — check the primary protocol.
- Next step
- Save the trial, show it to the treating physician, and confirm current recruitment with the study center. Costs, documents and travel →
Unsure about the terms? Read our patient guide →
Official title
Prospective Observational Study of Exhaled Carbon Monoxide Trajectories and Outcomes in ICU Patients
Overview
This is a single-center, prospective, observational study in adult intensive care unit (ICU) patients. The study will measure exhaled carbon monoxide (eCO) once daily for up to 7 days after ICU admission using a red blood cell lifespan breath analyzer, which simultaneously estimates erythrocyte lifespan. eCO is a gas produced endogenously during heme degradation and may reflect hemolysis, oxidative stress, and inflammation in critically ill patients. The purpose of this study is to describe how eCO changes over time in ICU patients and to determine whether different eCO patterns are associated with clinical outcomes. The primary outcome is all-cause mortality within 28 days after enrollment. Secondary outcomes include 90-day mortality, acute kidney injury, organ dysfunction assessed by SOFA score, transfusion requirement, changes in anemia-related indices, ICU length of stay, and duration of invasive mechanical ventilation. Participation does not change routine clinical care; study procedures involve breath sampling and collection of clinical data from the medical record.
Detailed description
Background: Endogenous carbon monoxide is generated in the human body and may increase during critical illness due to hemolysis, oxidative stress, and inflammation. Whether longitudinal patterns of exhaled carbon monoxide (eCO) provide prognostic information in critically ill patients remains unclear.
Design and setting: This is a single-center, prospective, observational cohort study conducted in an adult intensive care unit (ICU). The study is designed to characterize longitudinal eCO patterns and evaluate their clinical significance in critically ill patients without altering routine clinical management.
Study procedures and data collection: eCO will be measured once daily from Day 0 (baseline, within 24 hours of ICU admission/enrollment) through Day 7 when feasible, using a standardized breath analysis device. For patients receiving mechanical ventilation, breath sampling will be performed according to a standardized protocol for ventilated patients. In addition to serial eCO measurements, demographic characteristics, admission diagnosis, comorbidities, severity-of-illness scores, key treatments, and laboratory variables relevant to hemolysis, inflammation, organ function, anemia, and iron metabolism will be collected from the electronic medical record and protocol-defined assessments, as applicable.
Analytic approach: Group-based trajectory modeling (GBTM) will be used to identify distinct eCO trajectory groups from repeated measurements. Associations between eCO trajectories and prespecified clinical outcomes will be evaluated using Kaplan-Meier methods and multivariable Cox proportional hazards models with adjustment for clinically relevant covariates. Additional exploratory analyses will assess relationships between eCO trajectories and laboratory biomarker patterns, including anemia-related, iron metabolism-related, and inflammatory indices. Machine learning methods (e.g., XGBoost with SHAP-based interpretation) may also be used in exploratory analyses to develop risk prediction models incorporating eCO and other clinical variables.
Study conduct: No intervention is assigned as part of the study, and all treatment decisions remain at the discretion of the treating clinicians.
Primary outcome measures
- 28-day all-cause mortality [Time frame: From enrollment (Day 0) up to Day 28]
Secondary outcome measures (8)
- 90-day all-cause mortality [Time frame: From enrollment up to Day 90]
- Acute kidney injury (AKI) (KDIGO) [Time frame: From enrollment through ICU discharge (up to 28 days)]
- Organ dysfunction assessed by SOFA score [Time frame: Daily from Day 0 (baseline) through Day 7]
- Red blood cell transfusion requirement [Time frame: Up to 28 days after ICU admission/enrollment]
- ICU length of stay [Time frame: From ICU admission to ICU discharge (up to 90 days)]
- Duration of invasive mechanical ventilation [Time frame: From enrollment to liberation from invasive mechanical ventilation or ICU discharge (up to 28 days)]
- Complete blood count-related panel [Time frame: Up to 28 days after enrollment]
- Changes in iron metabolism related indices [Time frame: Baseline and up to 28 days after enrollment]
Eligibility criteria
Inclusion criteria
- Age ≥ 18 years
- Admitted to the intensive care unit (ICU) at the study site
- Expected ICU length of stay ≥ 48 hours
- Able to complete exhaled carbon monoxide (eCO) measurement (spontaneously breathing or mechanically ventilated)
- Written informed consent provided by the patient or a legally authorized representative
Exclusion criteria
- Carbon monoxide poisoning
- Active smoking within 24 hours prior to ICU admission
- Unable to perform breath sampling (e.g., massive airway bleeding, severe airway obstruction, extracorporeal membrane oxygenation)
- Ineffective sampling due to poor mask seal or special ventilation modes
- Pregnant or breastfeeding
- Known hereditary hemoglobinopathies (e.g., sickle cell disease, thalassemia)
- Patient or family refusal
- Other conditions deemed unsuitable by investigators
Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.
Healthy volunteers: No
Study design
- Observational model
- Cohort
Study locations
Center list to be confirmed — check the primary protocol.
Identifiers
NCT: NCT07454057 · B2026-018