Original ContributionBedside lung ultrasound in the assessment of alveolar-interstitial syndrome
Introduction
The alveolar-interstitial syndrome (AIS) of the lung includes several heterogeneous conditions with diffuse involvement of the interstitium and impairment of the alveolocapillary exchange capacity, which leads to more or less severe respiratory failure. Such conditions are either chronic (eg, pulmonary fibrosis) or acute (eg, acute respiratory distress syndrome (ARDS), acute pulmonary edema, interstitial pneumonia). Lung ultrasound is a noninvasive technique potentially useful in detecting AIS at bedside. Sonographic diagnosis of AIS relies on the detection of multiple and diffuse comet tail B lines at lung scans [1], [2], [3]. These are vertical artifacts fanning out from the lung-wall interface and spreading up to the edge of the screen (Fig. 1). They are due to thickened interlobular septa and extravascular lung water and have been found to be associated with bedside diagnosis of diffuse infiltrative lung diseases, pulmonary edema, and ARDS in critically ill patients [2]. Other authors found diffuse comet tail artifacts in patients with diffuse parenchymal lung disease [4], [5]. Jambrik et al [6] showed the usefulness of the artifacts as a nonradiologic sign of extravascular lung water. More recently, Agricola et al [7] showed that, in cardiac surgery patients without lung diseases, the number of comet tail images provides an estimate of extravascular lung water.
Detecting lung AIS is of great importance in the evaluation of dyspneic patients in the ED. Normally, diagnosis of AIS depends on pulmonary high resolution computerized scanning, but in the ED, we are usually dependent upon plain radiography. When chest x-ray is performed at bedside, it may be technically deficient. Nevertheless, it remains the only basis for taking therapeutic decisions. In the evaluation of dyspneic patients presented to the ED, plain film showed high specificity with low sensitivity in diagnosing congestive heart failure [8]. Lung ultrasound is easy to be implemented and potentially useful in detecting AIS at bedside. When performed by the attending emergency physicians, it is not time consuming and permits real-time assessment of dyspneic patients.
The present study aims at assessing the potential of bedside lung ultrasound to diagnose AIS in internal medicine inpatients and aims at estimating feasibility and interobserver agreement in the detection of B line artifacts.
Section snippets
Methods
The study was conducted at San Luigi community Hospital, Orbassano. It is a university hospital in the west side of Turin. The ED serves a primarily adult population with a volume of approximately 40,000 visits per year. The same emergency physician group attending the ED cover the 9 beds of the adult emergency medicine unit.
Results
Among 300 cases studied, ultrasound and chest radiograph findings could be compared in 295. In only 5 patients could a scan not be compared with plain film. They had noninterpretable ultrasound (2 patients with pneumonectomy in lung cancer and 2 patients with fibrothorax, because of lack of lung-wall interface) or noninterpretable radiograph (1 patient with mesothelioma, because of technically deficient image). In the 24 randomly selected patients who performed double ultrasound examination, we
Discussion
Some authors previously showed that comet tail artifacts type B at lung sonography generate through resonance due to multiple reflection of the beam from thickened interlobular septa to lung surface [2], [3], [4], [5], [6], [7], [9]. In a series of critically ill patients admitted to an intensive care unit, Lichtenstein et al [2] showed that the artifact and pulmonary subpleural thickened interlobular septa and/or ground-glass areas at CT were largely associated. The same authors observed that
Acknowledgment
The authors are grateful to Prof. Benedetto Terracini for his important help in translation of this work.
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