Diagnostic assessment of acute respiratory distress syndrome with lung ultrasound – comparison with Computed Tomography- preliminary data

Objectives: Lung ultrasound (LUS) is increasingly used in intensive care medicine to monitor invasive ventilation, however little data exists on the comparison of common lung ultrasound (LUS) findings in Acute Respiratory Distress Syndrome (“b-lines”, consolidations) with the imaging gold standard Computed Tomography (CT). Therefore the aim of our study was to examine these findings under controlled conditions at different Positive End Expiratory Pressure (PEEP) levels in healthy and diseased piglets and compare them with dynamic CT scans. Methods: After approval of the ethics comittee, 8 piglets were studied during pressure controlled mechanical ventilation before and after surfactant depletion injury. Inspiratory, expiratory and dynamic CT scans and ultrasound examinations were performed at defined PEEP levels (0, 5, 15) by one radiologist. (curved transducer 3.5 MHz, in oblique/transverse orientation at approx. 5th/6th intercostal space ventral and dorsal in the anterior axillary line on both sides and and additional transhepatic scans on the right side in 6 pigs). Offline evaluation of the CT images and ultrasound images was performed in separate sessions, blinded to the results. Results: Transhepatic ultrasound evaluation of lung consolidations as compared with CT showed an excellent correlation. Higher B-line counts were present in the diseased lung (compared with healthy lung), dorsally (compared with ventrally), and at lower PEEP levels (compared with higher PEEP levels). No CT correlate for the B-lines could be identified. Conclusion: Transhepatic assessment of consolidations for dynamic modification of respiratory management seems feasible with excellent CT correlation. B lines seemed to be influenced by respiratory parameters and position, however, no CT correlate could be found.