Excluding Pulmonary Embolism with End-tidal Carbon Dioxide: Accuracy, Cost, and Harm Avoidance

Area of Science:

• Pulmonary Medicine
• Diagnostic Imaging
• Critical Care

Background:

• Pulmonary embolism (PE) diagnosis often involves computed tomography pulmonary angiography (CTPA), which carries risks.
• Non-invasive methods to improve PE diagnostic accuracy and reduce healthcare costs are needed.

Purpose of the Study:

• To determine the optimal end-tidal carbon dioxide (EtCO2) threshold for excluding PE in hospitalized adults.
• To evaluate the financial impact and harm avoidance of incorporating EtCO2 into the PE diagnostic pathway.

Main Methods:

• A prospective, non-randomized, single-center study with a descriptive, correlational design.
• 111 hemodynamically stable hospitalized adults were assessed.
• PE diagnosis was confirmed using CTPA; EtCO2 levels were measured.

Main Results:

• PE prevalence was 18.9%. Mean EtCO2 was significantly lower in PE-positive patients (28 ± 7.8 mmHg) compared to PE-negative patients (33 ± 8.1 mmHg).
• An EtCO2 cutoff of ≥42 mmHg demonstrated 100% sensitivity, 12.2% specificity, and 100% negative predictive value for PE exclusion.
• Using EtCO2 could prevent unnecessary CTPA in 1 in 6 patients, avoiding radiation and contrast exposure.

Conclusions:

• An EtCO2 cutoff of ≥42 mmHg is a sensitive tool for excluding PE in stable hospitalized adults.
• Implementing EtCO2 monitoring can reduce unnecessary CTPA procedures, associated harms, and significant healthcare waste (~$88,000/year at this institution).