Diagnostic role of end-tidal carbon dioxide in differentiating chronic obstructive pulmonary disease and chronic heart failure: Association with NT-proBNP in dyspneic patients

Chronic heart failure (CHF) and chronic obstructive pulmonary disease (COPD) are increasingly prevalent among the elderly, and both frequently present with dyspnea as the primary symptom in emergency departments. Differentiating between the two conditions remains challenging, particularly in primary care, yet is essential given their distinct management approaches and prognostic implications. This study investigated the diagnostic utility of non-invasive end-tidal carbon dioxide (ETCO?) measurements in patients presenting with dyspnea and assessed whether combining ETCO? with N-terminal pro-brain natriuretic peptide (NT-proBNP) enhances diagnostic accuracy. A total of 205 patients admitted to the Emergency Department of Kayseri City Hospital and subsequently diagnosed with either CHF or COPD were included. Demographic data, clinical history, treatments, vital signs, NT-proBNP levels, echocardiographic findings, arterial blood gas results, integrated pulmonary index (IPI) scores, ETCO? values, and clinical outcomes were recorded. Echocardiography was performed by a cardiologist, and ETCO? and IPI values were obtained using the Medtronic Capnostream™ 35 monitor. NT-proBNP (p <0.001), ETCO? (p <0.001), and IPI (p = 0.038) were all statistically significant in differentiating CHF from COPD, with ETCO? demonstrating the strongest association. The addition of NT-proBNP or IPI to ETCO? did not provide further diagnostic benefit. NT-proBNP was also predictive of hospital admission (p <0.001). These findings indicate that quantitative ETCO? measurement, performed with a non-invasive and patient-friendly sidestream technique, is effective for diagnostic differentiation in acute dyspnea and has strong clinical applicability. ETCO? outperformed both NT-proBNP and IPI, and its use alone may be sufficient in this setting. Higher NT-proBNP cut-off values may be more appropriate in acute-onset dyspnea, and elevated NT-proBNP in COPD patients may hold prognostic value for poorer clinical outcomes.