Tag Archives: ultrasound

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?


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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21st November 2012: Accuracy of Point-of-Care US for Diagnosis of Elbow Fractures in Children

**Sincere apologies for the delay in this post (due 16th Nov, delayed by technical problems)**

Where can I find this paper?


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

How good is ultrasound at diagnosing elbow fractures in children?

Summary of the Paper

Design: prospective, observational, multi-centre diagnostic study

Objective: to determine the performance characteristics of ED ultrasound by PEM physicians for diagnosis of elbow fractures in children

Test under evaluation: ED (point-of-care) ultrasound of the elbow (scanning protocol pre-determined) to determine presence of lipohaemarthrosis OR elevated posterior fat pad

Reference standard: plain radiographs reported by radiologists blinded to ultrasound findings. Clinical follow-up with notes review or structured telephone follow-up; radiologist report used if follow-up imaging performed.

Primary outcome: determination of test characteristics

Population: convenience sample of patients aged up to 21yrs presenting to either of two urban EDs when a trained study physician was available, between Sept 2010 and Dec 2011.

  • Inclusion: possible elbow fracture requiring radiographic assessment
  • Exclusion: elbow radiographs already obtained, previous confirmed elbow fracture, open wound at the elbow, unstable vital signs, severe life threatening injuries requiring resuscitation.

Results: 130 patients enrolled, fracture present on initial ED radiography in 38/130. 5 additional fractures diagnosed on follow-up radiography (23 patients).

Elevated posterior fat pad was seen on initial XR in 57/130 patients (44%): 36 with fracture, 21 without (of whom, 4 patients had fracture identified on follow-up).

Elevated posterior fat pad OR lipohaemarthrosis was seen on ED US in 68/130 patients.

Elevated posterior fat pad OR lipohaemarthrosis gave the following test characteristics: sensitivity 98% (95% CI 88-100%), specificity 70% (95% CI 60-79%), PPV 0.62 (95% CI 0.50-0.72), NPV 0.98 (95% CI 0.91-1.0), LR+ 3.3 (95% CI 2.4-4.5), LR- 0.03 (95% CI 0.01-0.23)

Authors’ Conclusions:

With focused musculoskeletal ultrasonographic training, novice PEM sonologists were able to attain the skills necessary to perform point-of-care elbow ultrasonography to evaluate for fracture by assessing the posterior fat pad for elevation and lipohaemarthrosis. 

On the study design

Despite including “children” up to the age of 21 (!), there are many positive points about the methodology in this paper. The authors involved two centres over 16 months and although the sample was obtained as a convenience sample, the wide inclusion and few exclusions mean that there’s a good chance that the population is representative of patients seen in my ED.

There are reasonable attempts to minimise bias:

  • Standardised training
  • Blinding of radiologists to US results/clinical findings
  • Standardised data collection sheet for clinical/examination findings
  • Composite reference standard (telephone follow-up)

In addition, it seems pragmatic – with only 1hr training plus 5 practice scans PEM clinicians could achieve an agreement of 0.94 with an experienced PEM sonologist! What concerns me slightly is how unclear it is who these PEM clinicians were. We can all think of the colleagues who would jump at the chance to take part in a study like this; the fact that only one sonologist had prior experience of elbow ultrasound does NOT mean that the others were inexperienced with US in general. Would these results be reproducible in the hands of a not-quite-sure-which-end-of-the-probe-goes-where EM clinician – even with an hour of training? I’m not so sure…

However, the study is nicely designed and would be relatively easy to replicate in your own department.

What were the results and what does this mean?

For diagnostic studies, it can be helpful to draw a 2×2 table. This allows the calculation of test characteristics. Below is a 2×2 table for the presence of posterior fat pad OR lipohaemarthrosis on elbow US.

    Positive Negative Total
US Positive 42 26 68
Negative 1 61 62
Total 43 87 130

Sensitivity of 98% is not terrible, although the 95% confidence interval (88-100%) is pretty wide. This means the “true” sensitivity of elbow US in ED could be as low as 88%. Remember, high sensitivity means that when the test is negative we can effectively rule out the disease (fracture). Would we be happy to rule out at 88%? I don’t think so.

What’s most interesting is that the LR+ for elevated posterior fat pad AND lipohaemarthrosis is 5.8; that is, the proportion of patients who have a fracture and these findings is 5.8 times the proportion of patients with these findings who do not have a fracture. We can surmise that finding both elevated PFP and LH would be highly suggestive of an underlying fracture; but would this prevent an x-ray? Unlikely (pesky orthopods)! We don’t know quite how this correlates with the degree of required intervention (were these the fractures which needed to go to theatre; that were horrible looking supracondylar fractures from the outset?). And the LR- is not particularly brilliant when we look at the confidence intervals.

Not all patients who were followed-up had repeat XRs, but this reflects clinical practice and I think it is pretty reasonable not to XR a child who is pain-free with normal range of movement at their follow-up appointment. In fact, the radiation would be hard to justify. It is worth noting that four patients could not be followed-up; all had negative US and negative XR at their initial visit and were included in the “no fracture” group. The authors made reasonable attempts to follow-up these patients; how would the results be altered if we assumed the worst for these cases? And does it matter?

What can we take from this paper into clinical practice?

With appropriate training and practice, EM clinicians could use ultrasound to reliably exclude elbow fractures in children. However, a larger study is needed to tighten those confidence intervals; further training might also have this effect.

If both lipohaemarthrosis and elevated posterior fat pad are identified on US it is very likely that there is an underlying fracture, but would this change clinical practice? Probably not – yet 🙂

More questions to ask

  • Would more training/greater patient numbers narrow the confidence intervals (so we can effectively rule-out elbow fracture with ultrasound)?
  • Would the results be reproducible with a joe-bloggs ED clinician who’s a bit wobbly with an US probe (like me)?
  • Could we ever persuade orthopods to manage patients on the basis of US-diagnosed fractures without corresponding radiographs?

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