Bedside Ultrasound Versus Chest Radiography for Detection of Pulmonary Edema: A Prospective Cohort Study

Abstract

Objectives: Chest radiography has been the preferred imaging study to assess pulmonary congestion. However, chest radiography interpretation is influenced by the level of expertise and high interobserver variability. Lung ultrasound (US) may produce more objective findings through evaluation of vertical comet tail artifacts known as B-lines, which are created by a decrease in the ratio of alveolar air to fluid pulmonary content. Few studies have directly compared chest radiography to bedside US against a reference standard for the diagnosis of pulmonary edema. This study compared the sensitivity and specificity of bedside US and chest radiography in diagnosing pulmonary edema.

Methods: This prospective observational cohort study involved adult patients presenting to the emergency department of an urban tertiary hospital with dyspnea. The primary outcome was the presence or absence of pulmonary edema, as indicated by B-lines on a bedside lung US examination or radiologist-interpreted chest radiography. Patients underwent a US examination within about 1 hour of chest radiography. The final diagnosis from the discharge summary served as the reference standard.

Results: Ninety-nine patients were enrolled; 32.3% had congestive heart failure, and 40.4% had chronic obstructive pulmonary disease. Bedside US showed significantly higher sensitivity (96%) compared to chest radiography (65%; P < .001). Of 18 patients with negative radiographic findings and a discharge diagnosis of pulmonary edema, 16 (89%) had positive US findings (P < .001).

Conclusions: Bedside US has the potential to identify pulmonary edema more accurately than chest radiography. As current practice within the United States uses chest radiography, reflecting American College of Cardiology Foundation/American Heart Association guidelines for management of heart failure, the results of this study warrant further evaluation.

Keywords: dyspnea; heart failure; lung ultrasound; point-of-care testing; pulmonary edema; sensitivity and specificity.