Lung ultrasonography for the diagnosis of 11 patients with acute respiratory distress syndrome due to bird flu H7N9 infection

Abstract

Background: A novel reassortant avian-origin influenza A (H7N9) virus was found to infect three Chinese residents, the first H7N9 infection in humans in Asia. Chest computed tomography (CT) for acute respiratory distress syndrome (ARDS) diagnosis is not only expensive but also exposes patients to radiation and might cause patients to be at risk of infection during transportation; in addition, chest radiography cannot be used to monitor the lung repeatedly in real time. Therefore, the routine use of bedside lung ultrasonography for critically ill patients with ARDS is especially valuable.

Objectives: The aim of this study was to evaluate the application of ultrasound for lung examination in patients with ARDS.

Methods: Eleven patients infected with H7N9 avian influenza who developed ARDS were diagnosed by lung ultrasonography.

Results: Six patients who had severe ARDS showed a diffuse comet tail sign or a consolidation score ≥ 7 and a lung ultrasound score ≥ 20 points. A diffuse comet tail sign or a consolidation score ≤ 6 and a lung ultrasound score < 25 were observed in four patients. One patient showed a diffuse comet tail sign or consolidation area in four lung areas, with an ultrasound score of 14. Among all 11 patients studied, 6 patients had thoracic puncture and drainage of pleural effusion and 2 patients had pneumothorax puncture drainage.

Conclusions: Lung ultrasound could be useful for monitoring ARDS caused by the influenza virus A H7N9 strain in clinical applications.

Fig. 1

Lung sonography results. Patients with avian-origin influenza A (H7N9) virus were subjected to lung sonography analysis. □ B line; △ pleural effusion; ◯ consolidation; → air bronchography sign. a B line perpendicular to the pleura with a linear probe, namely, an isolated comet-tail sign. b: Four B lines with a linear probe, namely, a multiple comet-tail sign. c: Multiple comet-tail signs and pleural effusion with a convex array probe. d: Pleural effusion, lung consolidation, and air bronchography sign with a convex array probe. e: Disappearance of pleural sliding using a linear probe when the pneumothorax, stratosphere sign, and barcode sign were in the M modes

Fig. 2

Relationship between the lung sonogram score and the oxygenation index. The correlation between the lung sonogram score and the oxygenation index was analyzed by Microsoft Excel (2007), and a negative correlation with a correlation coefficient of −0.782 is shown