Probing Questions: Lung Ultrasound in Diagnosis and Management of Bronchiolitis

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Thanks to Casey Parker of Broomedocs for this guest contribution – his review is cross-posted here.

Where can I find this paper?

http://www.biomedcentral.com/1471-2431/15/63

What is this paper about (what is the research question)?

This paper aimed to correlate sonographic lung findings with clinically diagnosed bronchiolitis in infants.  The authors also attempted to provide some prognostic information [the need for oxygen support] based on sonographic lung features.

Summary of the Paper

The subjects were infants admitted for clinically suspected bronchiolitis.  There was also a cohort of “normal controls” used as a comparison.  The children underwent a clinical scoring by the treating Paediatrician and lung ultrasound by both a radiologist and Paediatrician sonographer.  The scans were all completed by two of the authors.

Design: Single-centre, observational cohort study conducted in an Italian Paediatric unit.

Objective: to evaluate the accuracy of lung ultrasonography in the diagnosis and management of bronchiolitis in infants.

Outcome of interest:  correlation between clinical and sonographic lung findings in bronchiolitic infants.  Can LUS findings be used to predict the need for supplemental oxygen requirements?

Participants: One hundred six infants, aged from 9 to 239 days old were enrolled.

  • Inclusions: clinically “suspected bronchiolitis” in infants.  Unclear as to whether these were consecutive cases – only 106 over a 3 year study period.
  • Exclusions: radiological pneumonia, other “concomitant pathology” or the unavailability of the study sonographer.

Results: There was a high level [ ~90%] of agreement between the clinician’s severity rating and the predetermined sonographic severity scores.  There was also a high level of agreement between the two sonographers scoring of the LUS findings (K = 89.6%).  The lung US scoring predicted the need for oxygen supplementation with good accuracy [sensitivity: 96.6 %, specificity 98.7 % ] although there were wide confidence intervals as a result of the small numbers in this trial.

Authors’ Conclusions:

In summary, this pilot study demonstrates that the use of LUS in bronchiolitis can be considered as an extension of the clinical evaluation and could be incorporated into clinical algorithms to aid decision-making. Our promising data needs to be confirmed in larger cohort studies also involving critical patients.

On the study design

 This study design is typical of many pilot ultrasound papers.  Small numbers of patients in which sonography is compared to a gold-standard that may not be entirely accurate of itself.  Bronchiolitis is a clinical diagnosis, with no really objective diagnostic standard.  The use of just 2 experienced Paediatric sonographers in a single centre does raise questions about the external validity of the results and there is a high likelihood of bias here.  The clinicians were blinded to the sonographic findings – and therefore the risk of bias here was removed.  The use of “normal cohort” and the “RSV swabs” in the study design was a little confusing and doesn’t really add to the results.

What were the results and what does this mean?

The results suggest that clinically diagnosed bronchiolitis looks like…. sonographic bronchiolitis as per the defined criteria used in this paper.  The protocol used did identify infants with more severe lung disease.  The need for supplemental oxygen was consistent with more severe LUS changes.  However, given the “standard” was clinical examination it is unclear exactly what LUS would add to the prognostication by paediatricians.  The high degree of agreement between the two study sonographers is difficult to extrapolate given they are both highly skilled, ultrasound enthusiasts – a larger mix of observers would be needed to draw any conclusions about our ability to utilise LUS in small kids.

What can we take from this paper into clinical practice?

Lung ultrasound for the diagnosis and severity scoring of bronchiolitis is reasonably accurate.  Does it add anything?  Probably not, unless you are currently using CXR to ‘diagnose’ bronchiolitis.  This paper does provide some useful descriptions of the spectrum of disease and their sonographic appearance.

I think this paper is interesting in that it describes the sonographic spectrum of a common disease of infants.  The study is not really large enough, nor does it have the external validity to make it a “practice changer”.   This pilot can help inform us about the appearance of bronchiolitis – and in the future this may become a more commonplace part of our clinical assessment of children – but for now I am not sure it adds to our quiver.

More questions to ask

  • Can ultrasound reliably differentiate bronchiolitis from important differential diagnoses in infants ? (e.g.. pneumonia, heart failure, upper airway obstruction… )
  • Are the sonographic findings in bronchiolitis consistent when obtained by sonographers of various experience?
  • Previous papers have compared LUS to conventional CXR for the diagnosis of bronchiolitis – and LUS was favourable.  It would be nice to see a paper looking at children with severe disease in which clinicians often turn to CXR to “reconfirm the working diagnosis” in order to ascertain its utility at that end of the spectrum.

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