SonoStudies: Thoracic Ultrasound for Pulmonary Embolism #FOAMed

Thoracic ultrasound is one of the most highly changing and advancing applications of bedside ultrasound, and the research that has been published on the utility of this application for our patients cannot be ignored. It can aid (and is better than chest Xray) in pneumothorax evaluation, pleural effusion assessment (only need 15cc of fluid to see it on ultrasound!), pneumonia evaluation, and pulmonary edema assessment. See prior posts here, here and here with literature referenced to read about all of that – trust me it’s worth it!). Of course, if you add cardiac echo to your evaluation for acute pulmonary embolism, the studies suggest it helps to look for McConnells sign and RV dilation and strain (which is a bad prognostic indicator for PE). Recently, there was a case report published in J of EM of a PE-in-transit diagnosed by bedside echo, leading to expedited care and ability to know the cause of suden cardiac arrest in a patient. For a clip of what it may look like for a “mobile mass” seen in RA, click here. Another study in J of EM was done concluding that ED bedside ultrasound echo results  predicted PE adverse outcomes.

Seeing RV dilation/strain can help but are seen mainly when the patient is hemodynamically unstable. Could thoracic ultrasound identify subsegmental pulmonary embolism in patients who are not hemodynamically unstable? Interesting question and I truly hope so…

So, if that wasnt enough, now it can help with pulmonary embolism evaluation??? What?! That is great and i hope that this teaser of a study below can be repeated and found to be valid. It would be great. Now, there have been a few others, like a meta-analysis showing that thoracic ultrasound should not be ignored when suspecting PE, a review of chest ultrasound for pulmonary diseases showing its utility, and a case report and review by the Italians (who are huge researchers in thoracic ultrasound where I listen to pretty much everything they say about it).

This recent study in Annals of Thoracic Medicine, physicians in Turkey evaluate the use of bedside ultrasound for the evaluation of pulmonary embolism. The abstract is below:

“OBJECTIVES: The diagnosis of pulmonary embolism (PE) is still a problem especially at emergency units. The purpose of study was to determine the diagnostic accuracy of thoracic ultrasonography (TUS) in patients with PE.

METHODS: In this prospective study, 50 patients with suspected PE were evaluated in Department of Pulmonary Diseases of a Training and Reasearch Hospital between January 2010 and July 2011. At the begining, TUS was performed by a chest physician, subsequently for definitive diagnosis computed tomography pulmonary angiography were performed in all cases as a reference method. Other diagnostic procedures were examination of serum d-dimer levels, echocardiography, and venous doppler ultrasonography of the legs. Both chest physician and radiologist were blinded to the results of other diagnostic method. Diagnosis of PE was suggested if at least one typical pleural-based/subpleural wedge-shaped or round hypoechoic lesion with or without pleural effusion was reported by TUS. Presence of pure pleural effusion or normal sonographic findings were accepted as negative TUS for PE.

RESULTS: PE was diagnosed in 30 patients. It was shown that TUS was true positive in 27 patients and false positive in eight and true negative in 12 and false negative in three. Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of TUS in diagnosis of PE for clinically suspected patients were 90%, 60%, 77.1%, 80%, and 78%, respectively.

CONCLUSIONS: TUS with a high sensitivity and diagnostic accuracy, is a noninvasive, widely available, cost-effective method which can be rapidly performed. A negative TUS study cannot rule out PE with certainty, but positive TUS findings with moderate/high suspicion for PE may prove a valuable tool in diagnosis of PE at bedside especially at emergency setting, for critically ill and immobile patients, facilitating immediate treatment decision.”

From the BLUE protocol by Lichtenstein on how to distinguish the various etiologies of shortness of breath, an algorithm was given (see below) which includes the utility of bedside ultrasound for pulmonary embolism diagnosis:

A Profile: anterior A lines bilaterally only – absence of interstitial syndrome – with lung sliding

A’ profile: A profile without lung sliding

B profile – anterior B lines bilaterally with lung sliding

B’ profile – B profile without lung sliding

A/B profile – A lines on one side and B lines present on the other side (asymmetry)

C profile – anterior consolidation (shred sign)

Normal – A profile without PLAPS

PLAPS = posterolateral alveolar and/or pleural syndrome

Thoracic US and the BLUE protocol

A good presentation on thoracic US for pulmonary embolism can be found here:

5 thoughts on “SonoStudies: Thoracic Ultrasound for Pulmonary Embolism #FOAMed

  1. Lichtestein is the “author” about US in critically ill. Anyway, with all respect, I think BLUE protocol must be like this…

    http://oi42.tinypic.com/2hp3jfp.jpg

    Lichtestein don´t use doppler in none of his US evaluation, but, today, it is a really important adjunt to bidimensional mode…
    The previously I mentioned about doppler is extracted from a great book “Chest Sonography” from Mathis G:

    http://oi43.tinypic.com/34y45yo.jpg

    “The lung infarction could be a correlate of pulmonary embolism. In the case of peripheral obstruction of branches of the pulmonary arteries and insucient nourishment from the bronchial arteries the patient may develop intra-alveolar hemorrhage which is visualized morphologically on the B-mode image as displaced air (Mathis and Dirschmid 1993). On qualitative color-Doppler sonography the lesion characteristically shows the absence of flow
    signals. On semiquantitative spectral analysis one occasionally finds a monophasic pattern close to the pleura; this pattern can be attributed to bronchial arteries. In some cases the disconnected supplying branch of the pulmonary artery is visualized.”
    http://oi42.tinypic.com/34hukbc.jpg

    Best

    • great points and some of Lichtenstein’s patient subjects did show exactly what you show in your version of the algorithm when reading the BLUE protocol on thoracic US (without doppler – as you state) and free veins definitely do not exclude PE in my opinion as well. There is another good presentation on this, stating what you describe as well found here: http://www.slideshare.net/basselericsoussi/thoracic-ultrasound-for-diagnosing-pulmonary-embolism . It would absolutely make sense that doppler would benefit the evaluation and in attempting to look for studies on this, I cannot find a good one – do you have any to provide?

      • Very good presentation. Like you, I didn´t find a doppler based study for thoracic US and PE, just the data in the book I previously mentioned. It is time to make an study about this? what is your opinion? Anyway, I think there is no problem to put doppler-on when a round or triangular hypoechoic subpleural consolidations is seen…
        Great discussion.
        Best
        PB

  2. Nice study. It is not easy to distinguish a consolidation pattern (BLUE “C” pattern) of a PE versus other etiologies (ex.pneumonia). Color doppler must be useful in that context, when a flow stops in the margins of consolidation (PE, pulmonary infarction) or flow is within the lesion (ex. pneumonia).
    Best

    • Hi PB – Thanks for your comment and yes, it can be difficult to distinguish hypoechoic consolidation from pneumonia patterns from hypoechoic area from a PE. Lichtenstein himself says that to increase your confidence with PE as a diagnosis, you should look for DVT. The key is also whether there are any B Lines – as his A profile (A lines seen only) should have you suspicious for PE – without B lines – whereas consolidation may have B lines. His shred sign of consolidation shows a hyperechoic outer pattern with the consolidation appearing hypoechoic – this is where a hypoechoic area of infarction (PE) may be confusing, requiring clinical correlation. From the BLUE protocol:
      “Pulmonary embolism does not yield interstitial change. A normal anterior lung surface was usually seen, as previously reported.29 None of 92 patients with anterior interstitial patterns had pulmonary embolism. The positive predictive value of deep venous thrombosis was 89%, but 94% if associated with the A profile, suggesting that the search for venous thrombosis should be associated with lung analysis.” Ive added the algorithm from Lichtenstein to the post as well.

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