title: Capnometry in suspected pulmonary embolism with positive D-dimer in the field.
abstract: BACKGROUND
  Pulmonary embolism (PE) is one of the greatest diagnostic challenges in prehospital emergency setting. Most patients with suspected PE have a positive D-dimer and undergo diagnostic testing. Excluding PE with additional non-invasive tests would reduce the need for further imaging tests. We aimed to determine the effectiveness of combination of clinical probability and end-tidal carbon dioxide (PetCO2) for evaluation of suspected PE with abnormal concentrations of D-dimer in prehospital emergency setting.
  
  
  METHODS
  We assessed clinical probability of PE and PetCO2 measurement in 100 consecutive patients with suspected PE and positive D-dimer in the field. PetCO2 > 28 mmHg was considered as the best cut-off point. PE was excluded or confirmed by hospital physicians in the University Clinical Center Maribor by computer tomography (CT), ventilation/perfusion scan echocardiography and pulmonary angiography.
  
  
  RESULTS
  PE was confirmed in 41 patients. PetCO2 had a sensitivity of 92.6% (95% CI, 79 to 98%), a negative predictive value of 94.2% (95% CI, 83 to 99%), a specificity of 83% (95% CI, 71 to 91%) and a positive predictive value of 79.2% (95% CI, 65 to 89%). Thirty-five patients (35%) had both a low (PE unlikely) clinical probability and a normal PetCO2 (sensitivity: 100%, 95% CI: 89 to 100%) and twenty-eight patients (28%) had both a high clinical probability (PE likely) and abnormal PetCO2 (specificity: 93.2%, 95% CI: 83 to 98%).
  
  
  CONCLUSIONS
  The combination of clinical probability and PetCO2 may safely rule out PE in patients with suspected PE and positive D-dimer in the prehospital setting.
authors.affiliation: University Clinical Centre Maribor, 2000 Maribor, Slovenia. tadeja.rumpf@gmail.com
authors.forename: Tadeja Hernja
authors.initials: TH
authors.lastname: Rumpf
authors.forename: Miljenko
authors.initials: M
authors.lastname: Krizmaric
authors.forename: Stefek
authors.initials: S
authors.lastname: Grmec
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019296:Capnography / Q000379:methods*; D002245:Carbon Dioxide / Q000032:analysis; D015331:Cohort Studies; D004635:Emergency Medicine; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis*; D006339:Heart Rate; D006469:Hemoptysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications; D018579:Patient Selection; D011237:Predictive Value of Tests; D011336:Probability; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000175:diagnosis* / Q000503:physiopathology; D012680:Sensitivity and Specificity
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D; D002245:Carbon Dioxide