Using End-Tidal CO₂ to Help Diagnose and Monitor Pulmonary Embolism

Assessment of End-Tidal CO₂ Levels in the Diagnosis and Management of Patients With Pulmonary Embolism

Pulmonary embolism (PE) can reduce blood flow in the lungs and impair gas exchange, leading to lower end-tidal carbon dioxide (EtCO₂) levels. This prospective observational study aims to evaluate whether EtCO₂ can help identify high-risk and intermediate-high-risk patients and monitor early treatment response, especially during thrombolytic therapy. A total of 120 participants were included: high-risk PE, intermediate-high-risk PE patients who received thrombolysis, intermediate-high-risk PE patients treated only with anticoagulation, and healthy controls.

The study measured EtCO₂ along with oxygen saturation, heart rate, respiratory rate, perfusion index, and radiological obstruction scores. By comparing these parameters at diagnosis and during the first 24 hours, the study seeks to determine whether EtCO₂ can serve as a simple, noninvasive marker of disease severity and early hemodynamic improvement in patients with acute PE.

Study Overview

• Status: Completed
• Conditions: Pulmonary Embolism Acute
• Intervention / Treatment: Other: thrombolytic therapy

• Study Type: Observational
• Enrollment (Actual): 120

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Erzurum, Turkey (Türkiye), 25200
    • Ataturk University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: N/A

• Sampling Method: Non-Probability Sample

Study Population

This study included adult patients diagnosed with acute pulmonary embolism who were classified as high-risk or intermediate-high-risk based on hemodynamic status, right ventricular dysfunction, and cardiac biomarker elevation. Participants were consecutively enrolled at a tertiary university medical center. The study also included a healthy control group composed of adults without cardiopulmonary disease or significant medical comorbidities. A total of 120 individuals were studied across four cohorts representing different clinical risk categories and routine treatment pathways.

Description

Inclusion Criteria:

Adults aged 18 years or older Diagnosis of acute pulmonary embolism confirmed by CT pulmonary angiography (for PE groups) Classified as high-risk or intermediate-high-risk pulmonary embolism according to ESC/ERS 2019 guidelines Ability to provide informed consent For healthy control group: no history of cardiopulmonary disease, coagulation disorders, or acute medical illness

Exclusion Criteria:

Known chronic respiratory diseases significantly affecting EtCO₂ measurement (e.g., advanced COPD, severe asthma, chronic respiratory failure) Active infection, sepsis, or acute complications of malignancy Prior thrombolytic therapy for pulmonary embolism Anatomical or technical limitations preventing reliable nasal capnography Pregnancy Individuals younger than 18 years Inability or refusal to provide informed consent

Study Plan

How is the study designed?

Number of groups / cohorts

4

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Group 1: High-Risk Pulmonary Embolism (Thrombolysis); Patients presenting with shock or persistent hypotension and receiving systemic thrombolytic therapy.	Other: thrombolytic therapy; Participants received standard clinical management according to current pulmonary embolism guidelines. No intervention was assigned by the investigators.
Group 2: Intermediate-High-Risk Pulmonary Embolism (Thrombolysis); Hemodynamically stable patients with RV dysfunction and elevated biomarkers who required thrombolysis.	Other: thrombolytic therapy; Participants received standard clinical management according to current pulmonary embolism guidelines. No intervention was assigned by the investigators.
Group 3: Intermediate-High-Risk Pulmonary Embolism (Non-Thrombolysis); Patients meeting intermediate-high-risk criteria but treated with anticoagulation only.
Group 4: Healthy Controls; Individuals without cardiopulmonary disease and with normal clinical and laboratory findings.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
End-Tidal Carbon Dioxide (EtCO₂) Level at Diagnosis	EtCO₂ level measured in mmHg using nasal capnography at the time of diagnosis to assess its ability to identify high-risk and intermediate-high-risk pulmonary embolism and to predict the need for thrombolytic therapy.	At baseline (within first 1 hour of diagnosis)

Collaborators and Investigators

• Sponsor: Ataturk University

Study record dates

Study Major Dates

• Study Start (Actual): February 1, 2025
• Primary Completion (Actual): July 30, 2025
• Study Completion (Actual): July 30, 2025

Study Registration Dates

• First Submitted: November 17, 2025
• First Submitted That Met QC Criteria: November 17, 2025
• First Posted (Estimated): November 21, 2025

Study Record Updates

• Last Update Posted (Actual): December 22, 2025
• Last Update Submitted That Met QC Criteria: December 19, 2025
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Therapeutics; Drug Therapy; Thrombolytic Therapy
• Other Study ID Numbers: B.30.2.ATA.0.01.00/427