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The Speed of Sound

The Speed of Sound: RADiUS to the Rescue for Patients with SOB

Butts, Christine MD

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doi: 10.1097/01.EEM.0000451956.24046.61
    Image 1
    Image 1:
    Image 1. M-mode tracing revealing normal lung sliding. The normally sliding lung is seen as the blurred lines (arrow) at the bottom of the image, indicating movement.

    We have been taking a close look at the RADiUS protocol for the past several months, but now it's time to put all of the pieces of the protocol together in assessing patients. RADiUS — rapid assessment of dyspnea with ultrasound — evaluates the heart, IVC, pleura, and lung parenchyma. It is a useful bedside tool for quickly assessing patients with undifferentiated shortness of breath, an extremely valuable tool for emergency physicians. These patients are challenging and require speedy appraisal and treatment.

    A 60-year-old man is brought to the ED by EMS complaining of shortness of breath for a past day. EMS has little history, but carries a bag of the patient's medications, which includes two inhalers, a diuretic, and an ACE inhibitor. The patient is in some distress, and is only able to speak a word or two at a time. His blood pressure is 180/90 mm Hg, heart rate is 120 bpm, respiratory rate is 40 bpm, and SpO2 is 80%. He is obese, and his breath sounds are diminished throughout but no wheezing is noted. He has questionable edema to his lower extremities, although his size makes this difficult to assess.

    Using the RADiUS protocol, we begin by evaluating his heart for overall contractility, pericardial effusion, and evidence of right heart strain. His overall left ventricular function is severely decreased. No effusion or right heart strain is noted.

    Image 2
    Image 2:
    Image 2. Low-frequency image of the lung parenchyma. Hyperechoic (white) B-lines are seen as vertical lines (arrow) emanating from the pleura (arrowhead). No A-lines are seen because they are obscured by the heavier B-lines.

    Shifting gears, we examine the IVC for overall size and change with respiration, and we see that the IVC is enlarged, and shows very little change with respiration. These findings correlate with an elevated central venous pressure.

    Using the high-frequency transducer, the pleura is assessed for sliding to evaluate for a possible pneumothorax. The ultrasound showed that the patient has normal lung sliding bilaterally, ruling out a pneumothorax. An M-mode tracing of the patient's pleura can be seen in Image 1, further confirming a normal pleural interface.

    Finally, evaluation of the lung parenchyma shows the presence of diffuse bilateral B-lines (Image 2), consistent with the interstitial syndrome.

    Putting all of these findings together gives a likely diagnosis of cardiogenic pulmonary edema, allowing the EP to initiate the correct treatment pathway rapidly. It also enables the EP to rule out other life-threatening causes of dyspnea, such as pericardial effusion.

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    The RADiUS Protocol: Videos and Past Articles

    Find the videos for this article on July 5 in the EMN iPad app and on July 12 in the Video Gallery on, where the EMN app can also be downloaded for free. Find all of Dr. Butts' RADiUS articles at

    © 2014 by Lippincott Williams & Wilkins