Chest
Volume 135, Issue 6, June 2009, Pages 1421-1425
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Original Research
Chest Ultrasonography
The Dynamic Air Bronchogram: A Lung Ultrasound Sign of Alveolar Consolidation Ruling Out Atelectasis

https://doi.org/10.1378/chest.08-2281Get rights and content

Background

The objective of this study was to identify the relationship between a dynamic lung artifact, the dynamic air bronchogram, within alveolar consolidation and the diagnosis of pneumonia vs resorptive atelectasis.

Methods

This prospective study was undertaken within the medical ICU of a university-affiliated teaching hospital. The sample comprised 52 patients with proven pneumonia (pneumonia group) and 16 patients with proven resorptive atelectasis (atelectasis group). All patients had alveolar consolidation with air bronchograms on lung ultrasound, were mechanically ventilated, and received fibroscopy and bacteriological tests. The air bronchogram dynamic was analyzed within the ultrasound area of consolidation.

Results

The air bronchograms in the pneumonia group yielded the dynamic air bronchogram in 32 patients and a static air bronchogram in 20. In the atelectasis group, air bronchograms yielded a dynamic air bronchogram in 1 out of 16 patients. With regard to pneumonia vs resorptive atelectasis in patients with ultrasound-visible alveolar consolidation with air bronchograms, the dynamic air bronchogram had a specificity of 94% and a positive predictive value of 97%. The sensitivity was 61%, and the negative predictive value 43%.

Conclusions

In patients with alveolar consolidation displaying air bronchograms on an ultrasound, the dynamic air bronchogram indicated pneumonia, distinguishing it from resorptive atelectasis. Static air bronchograms were seen in most resorptive atelectases and one third of cases of pneumonia. This finding increases the understanding of the pathophysiology of lung diseases within the clinical context and decreases the need for fibroscopy in practice.

Section snippets

Patients

Over a 6-year period, we prospectively studied patients who were critically ill, using the following selection criteria: admitted to a medical ICU, mechanically ventilated, having a suspected (by the managing team, blinded to the ultrasound results) pneumonia or resorptive atelectasis, receiving fibroscopy (ordered at the discretion of the managing team) that showed either an obstacle confirming the resorptive atelectasis (atelectasis group) or a satisfactory airway patency plus positive

Results

In the pneumonia group, ultrasound patterns of alveolar consolidation were located in the right lung in 34 patients, the left lung in 14 patients, and bilaterally in 4 patients. In the atelectasis group, they were located to the right in 4 patients and to the left in 12 patients. In the pneumonia group, a dynamic air bronchogram was observed in 32 patients and a static air bronchogram in 20 patients. In the atelectasis group, a dynamic air bronchogram was observed in 1 patient, and a static air

Discussion

The potential for an ultrasound to distinguish pneumonia from resorptive atelectasis comes first from its ability to document alveolar consolidation. In 98.5% of the patients, acute alveolar consolidations abutted the visceral pleura, creating the mandatory acoustic window for their ultrasound demonstration.5

In this study where all patients were mechanically ventilated, respiratory movement of gas bubbles within the bronchi indicate preserved patency of the airways because the gas bubbles are

Conclusions

In patients with ultrasound-visible alveolar consolidation displaying air bronchograms, the dynamic air bronchogram had a 94% specificity and a 97% positive predictive value for diagnosing pneumonia and distinguishing it from resorptive atelectasis. Static air bronchograms were seen in most resorptive atelectases and in one third of patients with pneumonia. Associated with the clinical data, this finding allows for a better understanding of the pathophysiology of lung diseases and, in some

Acknowledgment

The authors thank François Jardin for his trust.

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    The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/site/misc/reprints.xhtml).

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