Kline, Jeffrey A.Hogg, Melanie MCourtney, D MarkMiller, Chadwick DJones, Alan ESmithline, Howard AKlekowski, NicoleLanier, Randy2014-09-042014-09-042010-09Kline, J. A., Hogg, M. M., Courtney, D. M., Miller, C. D., Jones, A. E., Smithline, H. A., ... & Lanier, R. (2010). D-dimer and exhaled CO2/O2 to detect segmental pulmonary embolism in moderate-risk patients. American journal of respiratory and critical care medicine, 182(5), 669-675.https://hdl.handle.net/1805/4986Rationale: Pulmonary embolism (PE) decreases the exhaled end-tidal ratio of carbon dioxide to oxygen (etCO2/O2). Objectives: To test if the etCO2/O2 can produce clinically important changes in the probability of segmental or larger PE on computerized tomography multidetector-row pulmonary angiography (MDCTPA) in a moderate-risk population with a positive D-dimer. Methods: Emergency department and hospitalized patients with one or more predefined symptoms or signs, one or more risk factors for PE, and 64-slice MDCTPA enrolled from four hospitals. D-dimer greater than 499 ng/ml was test(+), and D-dimer less than 500 ng/ml was test(−). The median etCO2/O2 less than 0.28 from seven or more breaths was test(+) and etCO2/O2 greater than 0.45 was test(−). MDCTPA images were read by two independent radiologists and the criterion standard was the interpretation of acute PE by either reader. PE size was then graded. Measurements and Main Results: We enrolled 495 patients, including 60 (12%) with segmental or larger, and 29 (6%) with subsegmental PE. A total of 367 (74%) patients were D-dimer(+), including all 60 with segmental or larger PE (posterior probability 16%). The combination of D-dimer(+) and etCO2/O2(+) increased the posterior probability of segmental or larger PE to 28% (95% confidence interval [CI] for difference of 12%, 3.0–22%). The combination of D-dimer(+) and etCO2/O2(−) was observed in 40 patients (8%; 95% CI, 6–11%), and none (0/40; 95% CI, 0–9%) had segmental or larger PE on MDCTPA. No strategy changed the prevalence of subsegmental PE. Conclusions: In moderate-risk patients with a positive D-dimer, the et etCO2/O2 less than 0.28 significantly increases the probability of segmental or larger PE and the etCO2/O2 greater than 0.45 predicts the absence of segmental or larger PE on MDCTPA.en-USFibrin fragment Dvenous thromboembolismmedical decision makingpulmonary embolismArticle