Lungs;

Can pleural effusions be reliably detected using point-of-care ultrasound (POCUS)?

FA Manian MD, MPH, , , , , , , , Leave a comment

Absolutely. Though costophrenic blunting may not be seen on a PA or AP chest radiography until more than 200 mL of pleural effusion is present, as little as 20 mL of pleural fluid can be reliability detected with POCUS, with a sensitivity of 100% when more than 100 mL is present. Most pleural effusions will accumulate in the dependent areas within the chest cavity. Thus, in the usual semi-recumbent position used for POCUS, pleural effusion will accumulate above the diaphragm and below the lower lobe of the lungs.1,2

Few things to consider when evaluating for pleural effusion. 

  • Because evaluation for pleural effusions may require imaging depths of 10 to 20 cm, low frequency (preferably a phased array) transducer should be used.
  • Place the transducer in the posterior axillary line around the level of the diaphragm with the orientation marker positioned cephalad in the coronal plane (FIGURE 1).
  • Identify the diaphragm and use it as a point of reference to minimize mistakes such as labeling ascites as pleural effusion. Structures above the diaphragm (atelectatic lung, pleural effusion) will be shown on the left while structures below the diaphragm (abdominal organs, ascites) will be shown on the right side of the ultrasound display (FIGURE 2).
  • Keep in mind that freely flowing atelectatic lung tip (jellyfish sign) and spine shadows (spine sign) may be visible (VIDEO 1). Anechoic, free flowing pleural effusions are categorized as simple while homogeneously and heterogeneously echogenic effusions or those with septations are categorized as complex (VIDEO 2 and VIDEO 3). 2,3 
  • Smaller effusions may be seen as a small anechoic layer of fluid between the chest wall and the lung. If you use the M-mode, you will find that the lung moves towards or away from the chest wall in a wave like pattern (sinusoid sign) (VIDEO 4).1

Bonus Pearl: Did you know that you can estimate pleural effusion volume by using the following formula: Volume=16 x distance from mid lung base to the diaphragm (mm)? 4

Contributed by Woo Moon, D.O, Director, Hospitalist and Internal Medicine Residency Point-of-Care Ultrasound Programs, Mercy Hospital-St. Louis, St. Louis, Missouri

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     Figure 1                                                         Figure 2

Figure 3

Video 1

 

Video 2

 

Video 3

 

Video 4

 

References

  1. Soni NJ, Arntfield R, Kory P. Point of Care Ultrasound. 2nd ed. St. Louis, MO: Elsevier; 2019.
  2. Soni NJ, Franco R, Velez MI, et al. Ultrasound in the diagnosis and management of pleural effusions. J Hosp Med 2015;10(12):811–6. Ultrasound in the diagnosis and management of pleural effusions – PubMed (nih.gov) 
  3. Yang PC, Luh KT, Chang DB, Wu HD, et al. Value of sonography in determining the nature of pleural effusion: analysis of 320 cases. AJR Am J Roentgenol 1992;159(1):29–33.     Value of sonography in determining the nature of pleural effusion: analysis of 320 cases – PubMed (nih.gov)
  4. Usta E, Mustafi M, Ziemer G. Ultrasound estimation of volume of postoperative pleural effusion in cardiac surgery patients. Interact Cardiovasc Thorac Surg 2010;10(2):204–7. Ultrasound estimation of volume of postoperative pleural effusion in cardiac surgery patients – PubMed (nih.gov).

Disclosures/Disclaimers: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis, Massachusetts General Hospital, Harvard Catalyst, Harvard University, their affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

Can pleural effusions be reliably detected using point-of-care ultrasound (POCUS)?

Is lung ultrasound useful in evaluating patients with dyspnea?

FA Manian MD, MPH, , , , , , , , , , , , Leave a comment

Yes! Increasingly, lung ultrasound (particularly point-of-care ultrasound-POCUS) is performed at bedside to help explain the cause of dyspnea.  Here are some tips.

First, obtain images by placing the transducer in the intercostal space (usually 3 regions/hemithorax) with the orientation marker pointing cephalad. 1,2  Now look at the pleural line, the horizontal hyperechoic structure between 2 ribs  (Figure 1). To and fro movement of the pleural line reflects apposition of the visceral and parietal pleura and is a normal finding (“lung sliding”).  Then look for additional horizontal hyperechoic lines visualized deep to the pleural line (“A-lines”) which are reverberation artifacts, reflecting air below the pleura (Clip/Figure 1).2 

You should also look for vertical laser like hyperechoic artifacts that arise from the pleural line and extend to the bottom of the display which may represent  “comet tails” or “B-lines” (Clip/Figure 2).1,3,4 These are reverberation artifacts created by the acoustic impedance difference between widened, fluid filled septa and air-filled alveoli.3,5  Three or more B-lines within a single intercostal space is considered pathological.4

One of the practical uses of lung ultrasound is in the evaluation of dyspnea in a patient with Chronic Obstructive Pulmonary Disease (COPD).6 The presence of lung sliding and bilateral A-lines in the absence of B-lines can help rule out pneumothorax, pneumonia and pulmonary edema and steer you toward other diagnoses (eg, COPD exacerbation) as cause of dyspnea.

You can even take it a step further. Focal unilateral B-lines suggest possible pneumonia while diffuse bilateral B-lines (interstitial syndrome) would be more consistent with pulmonary edema.

As usual, the patient’s history, physical examination and available laboratory data must be taken into consideration when interpreting lung ultrasound findings.2,4

Contributed by Woo Moon, D.O., Department of Medicine, Mercy-St. Louis, St. Louis, Missouri

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Figure 1 

 

 

Clip 1

 

 

Figure 2

 

Clip 2

 

References

  1. Lichtenstein DA. Lung ultrasound in the critically ill. Ann Intensive Care 2014;4(1): https://pubmed.ncbi.nlm.nih.gov/24401163/ 
  2. Soni MD MS NJ, Arntfield MD FRCPC R, Kory MD MPA P. Point of Care Ultrasound. 2nd ed. St. Louis, MO: Elsevier; 2019.
  3. Lichtenstein DA, Mezière GA. Relevance of lung ultrasound in the diagnosis of acute respiratory failure: the BLUE protocol. Chest 2008;134(1):117–25. https://pubmed.ncbi.nlm.nih.gov/18403664/ 
  4. Volpicelli G, Elbarbary M, Blaivas M, et al. International evidence-based recommendations for point-of-care lung ultrasound. Intensive Care Med 2012;38(4):577–91. https://pubmed.ncbi.nlm.nih.gov/22392031/ 
  5. Lichtenstein D, Mézière G, Biderman P, Gepner A, Barré O. The comet-tail artifact. An ultrasound sign of alveolar-interstitial syndrome. Am J Respir Crit Care Med 1997;156(5):1640–6. https://pubmed.ncbi.nlm.nih.gov/9372688/
  6. Qaseem A, Etxeandia-Ikobaltzeta I, Mustafa RA, et al. Appropriate Use of Point-of-Care Ultrasonography in Patients With Acute Dyspnea in Emergency Department or Inpatient Settings: A Clinical Guideline From the American College of Physicians. Ann Intern Med 2021;174(7):985–93. https://www.acpjournals.org/doi/10.7326/m20-7844 

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis, Massachusetts General Hospital, Harvard Catalyst, Harvard University, their affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

Is lung ultrasound useful in evaluating patients with dyspnea?

What is the utility of pulmonary auscultation for crackles (rales) in diagnosing congestive heart failure (CHF) or pneumonia?

FA Manian MD, MPH, , , , , , 1 Comment

The evidence for the accuracy of crackles in CHF is not as robust as often assumed, with wide variations in its sensitivity (13%-70%), specificity (35%-100%), positive predictive value (19%-100%), and negative predictive value (17%-85%) (1).

In a study  of patients at high risk for CHF but without valvular heart disease, symptoms of CHF, or comorbid pulmonary disease,  the prevalence of baseline crackles in one or both lungs increased with age: 45-64 y , 11%; 65-79 y, 34%; and 80-95 y, 70%.  At best, fair or poor positive and negative likelihood ratios (LRs) have been reported for crackles in CHF (3.4, and 0.8, respectively) (2). 

The accuracy of crackles in diagnosing pneumonia in patients with cough and fever is not much better: sensitivity 19-67%, specificity 36-94%, and poor positive and negative LRs (1.8 and 0.8, respectively) (2).

So don’t overestimate the accuracy of crackles in CHF or pneumonia, especially if your suspicion for these conditions is high!

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References

  1. Kataoka H, Matsuno O. Age-related pulmonary crackles (rales) in asymptomatic cardiovascular patients. Ann Fam Med 2008;6:239-245.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2384982/ 
  2. McGee S. Auscultation of the lungs. In Evidence-based physical diagnosis (3rd ed.). Elsevier Saunders, Philadelphia, 2012.
What is the utility of pulmonary auscultation for crackles (rales) in diagnosing congestive heart failure (CHF) or pneumonia?