title: Ambulatory vital signs in the workup of pulmonary embolism using a standardized 3-minute walk test.
abstract: OBJECTIVE
  Diagnosing pulmonary embolism can be difficult given its highly variable clinical presentation. Our objective was to determine whether a decrease in oxygen saturation or an increase in heart rate while ambulating could be used as an objective tool in the diagnosis of pulmonary embolism.
  
  
  METHODS
  This was a two-site tertiary-care-centre prospective cohort study that enrolled adult emergency department or thrombosis clinic patients with suspected or newly confirmed pulmonary embolism. Patients were asked to participate in a standardized 3-minute walk test, which assessed ambulatory heart rate and ambulatory oxygen saturation. The primary outcome was pulmonary embolism.
  
  
  RESULTS
  We enrolled 114 patients, including 30 with pulmonary embolism (26.3%). A ≥2% absolute decrease in ambulatory oxygen saturation and an ambulatory change in heart rate >10 beats per minute (BPM) were significantly associated with pulmonary embolism. An ambulatory heart rate change of >10 BPM had a sensitivity of 96.6% (95% confidence interval [CI] 83.3 to 99.4) and a specificity of 31.0% (95% CI 22.1 to 45.0) for pulmonary embolism. A ≥2% absolute decrease ambulatory oxygen saturation had a sensitivity of 80.2% (95% CI 62.7 to 90.5) and a specificity of 39.3% (95% CI 29.5 to 50.0) for pulmonary embolism. The combination of both variables yielded a sensitivity of 100.0% (95% CI 87.0 to 100.0) and a specificity of 11.0% (95% CI 6.6 to 21.0).
  
  
  CONCLUSIONS
  In summary, our study found that an ambulatory heart rate change of >10 BPM or a ≥2% absolute decrease in ambulatory oxygen saturation from baseline during a standardized 3-minute walk test are highly correlated with pulmonary embolism. Although the findings appear promising, neither of these variables can currently be recommended as a screening tool for pulmonary embolism until larger prospective studies examine their performance either alone or with pre-existing rules.
authors.affiliation: *Department of Emergency Medicine,Department of Medicine,Ottawa Hospital Research Institute,University of Ottawa,ON.
authors.forename: Qamar
authors.initials: Q
authors.lastname: Amin
authors.affiliation: *Department of Emergency Medicine,Department of Medicine,Ottawa Hospital Research Institute,University of Ottawa,ON.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Perry
authors.affiliation: *Department of Emergency Medicine,Department of Medicine,Ottawa Hospital Research Institute,University of Ottawa,ON.
authors.forename: Ian G
authors.initials: IG
authors.lastname: Stiell
authors.affiliation: *Department of Emergency Medicine,Department of Medicine,Ottawa Hospital Research Institute,University of Ottawa,ON.
authors.forename: Subhra
authors.initials: S
authors.lastname: Mohapatra
authors.affiliation: *Department of Emergency Medicine,Department of Medicine,Ottawa Hospital Research Institute,University of Ottawa,ON.
authors.forename: Abdulaziz
authors.initials: A
authors.lastname: Alsadoon
authors.affiliation: †Division of Hematology Clinical Epidemiology Program,Ottawa Hospital Research Institute,University of Ottawa,ON.
authors.forename: Marc
authors.initials: M
authors.lastname: Rodger
mesh_terms: D000328:Adult; D000368:Aged; D004636:Emergency Service, Hospital; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010045:Outpatients; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000175:diagnosis*; D012129:Respiratory Function Tests; D013997:Time Factors; D016138:Walking / Q000502:physiology*
keywords: Ambulatory Vital Signs; Pulmonary Embolism; Walk-test