Ambulatory vital signs in the workup of pulmonary embolism using a standardized 3-minute walk test

CJEM. 2015 May;17(3):270-8. doi: 10.1017/cem.2014.45.

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).

Conclusion: 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.

Keywords: Ambulatory Vital Signs; Pulmonary Embolism; Walk-test.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Emergency Service, Hospital*
  • Exercise Test
  • Female
  • Follow-Up Studies
  • Humans
  • Male
  • Middle Aged
  • Outpatients*
  • Prospective Studies
  • Pulmonary Embolism / diagnosis*
  • Respiratory Function Tests
  • Time Factors
  • Walking / physiology*