Assessment of end-tidal CO₂ levels in the diagnosis and management of patients with pulmonary embolism

Abstract

Pulmonary embolism (PE) is a life-threatening emergency associated with acute cardiopulmonary deterioration. This study evaluated the clinical utility of end-tidal carbon dioxide (EtCO₂) for assessing disease severity and monitoring treatment response in high- and intermediate–high-risk PE. This prospective study (registry ID: NCT07241130) included 120 individuals presenting between February and July 2025, categorized into four groups: high-risk PE with thrombolysis, intermediate–high-risk PE with thrombolysis, intermediate–high-risk PE without thrombolysis, and healthy controls. Physiological parameters were measured using the Rad-97 monitor under standardized conditions. Baseline EtCO₂ levels differed significantly among the groups ( p < 0.001). The lowest mean EtCO₂ value was observed in the high-risk PE group (15.2 ± 1.9 mmHg) and the highest in the control group (31.8 ± 3.1 mmHg). After 24 h of treatment, there were no significant differences among the groups in terms of EtCO₂, peripheral oxygen saturation (SpO₂), or perfusion index (PI) values ( p > 0.05). EtCO₂ was negatively correlated with pulmonary artery obstruction index ( r = − 0.358, p = 0.01) and positively correlated with SpO₂ ( r = 0.594, p < 0.001) and PI ( r = 0.431, p < 0.001). ROC analysis identified an optimum EtCO₂ cutoff of 17.5 mmHg to discriminate between patients with and without thrombolytic therapy (97% sensitivity, 85% specificity). EtCO₂ is a simple, noninvasive physiological marker associated with thrombus burden and treatment-related changes in PE. Rather than determining therapeutic decisions, EtCO₂ may complement established clinical and imaging parameters by providing supportive physiological information in acute settings. ClinicalTrials.gov Identifier: NCT07241130. Retrospectively registered.