Lung Ultrasound a reliable and efficient beside diagnostic tool for detecting ARDS, finds study

Acute respiratory syndrome (ARDS) is a life-threatening condition and one of the major cause of mortality in critically ill patients. Lung ultrasound has gained popularity in recent days for the diagnosis of ARDS. In a recent Italian study, researchers have suggested that lung ultrasound is reliable and efficient beside diagnostic tool that may allow bedside detections of the morphologic patterns in acute respiratory distress syndrome should be more widely used. However, the statement was opposed by U.S researchers stating that using lung ultrasound as a bedside tool posses various challenges which limit there use, especially in the U.S.

Dr Davide Chiumello of the University of Milan and colleagues conducted a single-center study of 32 sedated, paralyzed ARDS patients (62.5% men) with a mean age of 65, mean BMI of 25.9, and mean Pao2/Fio2 of 139.

Computed tomography (CT) and lung US were performed at a positive end-expiratory pressure of 5 cm H2O. A standardized assessment of six regions per hemithorax was used; each region was classified for the presence of normal aeration, alveolar-interstitial syndrome, consolidation, and pleural effusion.

The team calculated agreement between the two techniques and assessed diagnostic variables for US using CT as a reference.

As reported online August 26 in Critical Care Medicine, a global agreement between lung US and CT ranged from 0.640 to 0.934, and was 0.775 on average.

Overall, US sensitivity ranged from 82.7% to 92.3% and specificity, from 90.2% to 98.6%. Results were similar with regional analysis.

US diagnostic accuracy was significantly higher when morphologic patterns not reaching the pleural surface were excluded, with areas under the receiver operating characteristic curve of 0.854 versus 0.903 for the alveolar-interstitial syndrome, and 0.851 versus 0.896 for consolidation.

"Lung ultrasound is a reproducible, sensitive, and specific tool, which allows for bedside detections of the morphologic patterns in acute respiratory distress syndrome," the authors state. "The presence of deep lung alterations may impact the diagnostic performance of this technique."

Dr. Baskaran Sundaram, Director of Cardiothoracic Imaging at Thomas Jefferson University in Philadelphia, told Reuters Health by email, "(Lung) US has limitations, including poor sound wave penetration through the air in the lungs and rib cage, and operator dependence. Obesity, emphysema, chest wall deformity, lines' drain tubes, and support devices over the patients pose additional challenges."

All patients were in the early phase of ARDS, he noted. In this phase, "the lungs have a significant amount of acute inflammatory exudates which may accentuate the performance of (lung) US. As ARDS evolves, inflammatory exudates subside, and fibrosis ensues, which may negatively influence the performance of (lung) US."

Consolidation (pneumonia and aspiration) caused ARDS in most of the study patients, he said. "The texture of the lungs during these conditions becomes similar to the liver or spleen. There was also a significant amount of patients with pleural effusion." Both of those factors may artificially enhance the performance of US, he noted.