Chest radiography versus lung ultrasound for identification of acute respiratory distress syndrome: a retrospective observational study

Kay Choong See,Juvel Taculod,Juliet Sahagun,Venetia Ong,Yi Lin Tan

doi:10.1186/s13054-018-2105-y

Abstract

BackgroundLung ultrasound may be a reasonable alternative to chest radiography for the identification of acute respiratory distress syndrome (ARDS), but the diagnostic performance of lung ultrasound for ARDS is uncertain. We therefore analyzed the clinical outcomes of ARDS diagnosed according to the Berlin Definition, using either chest radiography (Berlin-CXR) or lung ultrasound (Berlin-LUS) as an alternative imaging method.MethodsThis was a retrospective observational study in a 20-bed medical intensive care unit (ICU). Patients who required noninvasive ventilation or invasive ventilation for hypoxemic respiratory failure on ICU admission from August 2014 to March 2017 were included. Both chest radiography and lung ultrasound were performed routinely upon ICU admission. Comparisons were made using either the Berlin-CXR or Berlin-LUS definitions to diagnose ARDS with respect to the patient characteristics and clinical outcomes for each definition. ICU and hospital mortality were the main outcome measures for both definitions.ResultsThe first admissions of 456 distinct patients were analyzed. Compared with the 216 patients who met the Berlin-CXR definition (ICU mortality 19.4%, hospital mortality 36.1%), 229 patients who met the Berlin-LUS definition (ICU mortality 22.7%, hospital mortality 34.5%) and 79 patients who met the Berlin-LUS but not the Berlin-CXR definition (ICU mortality 21.5%, hospital mortality 29.1%) had similar outcomes. In contrast, the 295 patients who met either definition had higher mortality than the 161 patients who did not meet either definition (ICU mortality 20.0% versus 12.4%, P = 0.041; hospital mortality 34.2% versus 24.2%, P = 0.027). Compared with Berlin-CXR, Berlin-LUS had a positive predictive value of 0.66 (95% confidence interval 0.59–0.72) and a negative predictive value of 0.71 (0.65–0.77). Among the 216 Berlin-CXR ARDS patients, 150 patients (69.4%) also fulfilled Berlin-LUS definition.ConclusionsFor the identification of ARDS using the Berlin definition, both chest radiography and lung ultrasound were equally related to mortality. The Berlin definition using lung ultrasound helped identify patients at higher risk of death, even if these patients did not fulfill the conventional Berlin definition using chest radiography. However, the moderate overlap of patients when chest imaging modalities differed suggests that chest radiography and lung ultrasound should be complementary rather than used interchangeably.

Highlights

Lung ultrasound may be a reasonable alternative to chest radiography for the identification of acute respiratory distress syndrome (ARDS), but the diagnostic performance of lung ultrasound for ARDS is uncertain
Among the 66 patients who met the Berlin-Chest radiography (CXR) definition for ARDS but not the Berlin-LUS definition, 61 (92.4%) had CXR opacities not detected by lung ultrasound, while 5 (7.6%) patients had apparent consolidation on CXR that was found to be pleural effusion
ARDS acute respiratory distress syndrome, CXR chest radiography, ICU intensive care unit, LUS lung ultrasound aMild ARDS: ratio of arterial partial pressure of oxygen to inspired fraction of oxygen (P/F) 201–300 mmHg and positive end-expiratory pressure (PEEP)/continuous positive airway pressure (CPAP) ≥5 cmH2O using noninvasive ventilation or invasive mechanical ventilation (IMV); moderate ARDS: P/F 101–200 mmHg and PEEP ≥ 5 cmH2O using IMV only; severe ARDS: P/F ≤ 100 mmHg and PEEP ≥ 5 cmH2O using IMV only identification using a combined approach resulted in a 37% increase in the number of ARDS cases over the Berlin-CXR definition alone while maintaining a specificity of 67%

Summary

Introduction

Lung ultrasound may be a reasonable alternative to chest radiography for the identification of acute respiratory distress syndrome (ARDS), but the diagnostic performance of lung ultrasound for ARDS is uncertain. We analyzed the clinical outcomes of ARDS diagnosed according to the Berlin Definition, using either chest radiography (Berlin-CXR) or lung ultrasound (Berlin-LUS) as an alternative imaging method. The current diagnostic criteria for ARDS follows the Berlin definition, which requires chest radiography or computed tomography for determination of bilateral pulmonary infiltrates [1]. The Kigali Modification of the Berlin definition has been proposed which, among other changes, allows for either chest radiography or lung ultrasound to be used for the determination of bilateral pulmonary infiltrates [2]. Chest radiography has poor sensitivity for the detection of pulmonary infiltrates compared with other imaging modalities such as computed tomography [3]. Chest radiography may not be available in resource-limited settings, or in austere environments, and requires the use of radiation [5]

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