End Tidal Carbon Dioxide as a Screening Tool for Computed Tomography Angiogram in Postoperative Orthopaedic Patients Suspected of Pulmonary Embolism.
Computed tomography pulmonary angiography (CTA) is the gold standard for diagnosing pulmonary embolism (PE) but involves radiation and iodinated contrast exposure. Of orthopedic patients evaluated for PE, a minority have a positive CTA study. Herein, we evaluate end tidal carbon dioxide (ETCO2) as a method to identify patients at low risk for PE and may not require a CTA. We hypothesize that ETCO2 will be useful for predicting the absence of PE in postoperative orthopedic patients.



In this prospective study, all patients older than 18 years who were admitted for orthopedic surgery and who had a CTA performed for PE were eligible. These patients underwent an ETCO2 measurement. Patients were determined to have PE if they had a positive PE-protocol CT.



Between May 2014 and April 2015, 121 patients met the inclusion criteria for the study. Of these patients, 84 had a negative CTA examination, 25 had a positive examination, and 12 had a nondiagnostic examination. We found a statistically significant difference (P = .03) when comparing the average ETCO2 values for the positive and negative CTA groups. An ETCO2 cutoff value of 43 mm Hg was 100% sensitive with a negative predictive value of 100% for absence of PE on CTA.



This study demonstrates a significant difference in ETCO2 measurements between postoperative orthopedic patients with and without CTA-detected PE. A cutoff value of >43 mm Hg may be useful in excluding patients from undergoing CTA.
Department of Orthopaedic Surgery, New York University Hospital for Joint Diseases, New York, New York.
Austin J
AJ
Ramme
Department of Internal Medicine, New York University Langone Medical Center, New York, New York.
Eduardo
E
Iturrate
Department of Internal Medicine, New York University Langone Medical Center, New York, New York.
Ezra
E
Dweck
Department of Internal Medicine, New York University Langone Medical Center, New York, New York.
David J
DJ
Steiger
Department of Orthopaedic Surgery, New York University Hospital for Joint Diseases, New York, New York.
Lorraine H
LH
Hutzler
Department of Population Health, New York University Langone Medical Center, New York, New York.
Yixin
Y
Fang
Department of Population Health, New York University Langone Medical Center, New York, New York.
Binhuan
B
Wang
Department of Orthopaedic Surgery, New York University Hospital for Joint Diseases, New York, New York.
Joseph A
JA
Bosco
Department of Internal Medicine, New York University Langone Medical Center, New York, New York.
Alana E
AE
Sigmund
D000368:Aged; D000792:Angiography; D001944:Breath Tests; D002245:Carbon Dioxide / Q000032:analysis*; D000072226:Computed Tomography Angiography; D003287:Contrast Media; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000009:adverse effects*; D009985:Orthopedics; D011184:Postoperative Period; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000175:diagnosis* / Q000209:etiology
D003287:Contrast Media; D002245:Carbon Dioxide
capnography; diagnostic tool; orthopedic surgery; peri-operative; prospective study; pulmonary embolism