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October 20, 2019

Stephanie Conner MD

Point of Care Ultrasound Lung Ultrasound

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Objectives

• Basic principles of lung ultrasound• Key lung ultrasound findings• Brief overview of thoracentesis windows

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Objectives

• Basic principles of lung ultrasound• Key lung ultrasound findings• Brief overview of thoracentesis windows

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Probe Selection

Linear

• Superficial depth• High resolution• Ideal for evaluating the

pleural line, lung sliding

Phased array

• Deeper depth• Lower resolution• Ideal for evaluating a-

lines, b-lines, consolidations, and effusions

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Patient Position: Ambulatory

Chest. 2011;140(5):1332-1341. doi:10.1378/chest.11-0348

Hospitalized Patient Technique

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Anatomy of Lung Ultrasound

Skin & soft tissue

Ribs

Pleural line

Intercostal space

Key Learning Point

Ultrasound cannot visualize through bone or air. Therefore, everything we see in lung

ultrasound is either:

Artifact or Abnormal- A-lines

- Rib shadow

- B-lines- Consolidation- Pleural Effusion

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Lung scatter & A-lines

Ultrasound scatters in air, so you can’t see through it

Rib shadowing

Rib shadow

Ultrasound cannot penetrate through bone, so you can’t visualize deep to it.

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Key Learning Point

Ultrasound cannot visualize through bone or air. Therefore, everything we see in lung

ultrasound is either:

Artifact or Abnormal- A-lines

- Rib shadow

- B-lines- Consolidation- Pleural Effusion

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Objectives

• Basic principles of lung ultrasound• Key lung ultrasound findings (5)• Brief overview of thoracentesis windows

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A-lines (1 of 5)

Reverberations between the highly reflective pleura and transducer

Can be seen in any LZ

DDx: • Normal • If no lung sliding:

PTX• If hypoxic/dyspneic:

asthma, COPD, PE

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A- vs. B-lines

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B-lines (2 of 5)

Propogation of US waves through the lungs 2/2 widening of the interlobular septa

Differential diagnosis:• Pulmonary edema• Pneumonia• ILD• ARDS

>3 b-lines in >2 zones bilaterally = interstitial syndrome.• 94% sensitivity, 92%

specificity for pulmonary edema

Features of B-lines

• Arise from the pleural line

• Obliterate a-lines

• Move with lung sliding

• Extend >12cm• Abnormal >3 in

one LZ

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Clinical Correlation of B-lines

Liteplo et al. Real-time resolution of sonographic B-lines in a patient with pulmonary edema on CPAP. AJEM (2010)

• Case: Hx CHF, ESRD, dyspnea, orthopnea

• Initial US: Diffuse B-lines• After CPAP x 3.5hrs: A-lines

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Alveolar Consolidation (3 of 5)

• “Hepatization of lung”

• Ddx: PNA vs atelectasis

• Clinical correlation, other POCUS signs (shred sign, air bronchograms) needed

* Real world note: probably the most challenging application of lung US

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Case: 50 y/o male with cough & fever

Liver

Pleural Effusion (4 of 5)

• Identification of a hypoechoic or echo-free space surrounded by typical anatomic boundaries

• Costophrenic angles bilaterally (LZ 4)• Simple vs complex

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RUQ/Perihepatic view:Normal

Morison’s Pouch

Costophrenic Recess

Diaphragm

Pleural Effusion

Typical anatomic boundaries:• Diaphragm (and abdominal

organs)• Chest wall• Ribs• Visceral pleura• Lung

Spine sign

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Simple vs complex effusions

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Pleural Effusion

US more sensitive than XR or exam: • Exam > 300mL• CXR >200mL• US > 20 mL

Scan dependent zones

Fluid is hypoechoic (black)

Spine sign

Effusion

Lung

Liver

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Lung Findings Summary

• US for B-lines, consolidation, and pleural effusion = more sensitive than physical exam or CXR

• Faster to acquire than CXR

• Less radiation

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Pneumothorax (5 of 5)

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Key Principle: Lung Sliding

Movement of visceral pleura against parietal pleura with respiratory motion

Linear probe

B- and M-mode

Findings:

Syndrome Lung sliding? A-lines? B-lines?

Normal √ √

Pneumothorax √

Pneumonia ± √

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Is Pleural Sliding

Present?

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Is Pleural Sliding

Present?

Pneumothorax

When in doubt… M-mode

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SoftTissue

NormalLung Beach

Ocean

Normal M-mode of Lung

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SoftTissue

AbnormalLung

Ocean / Barcode

Abnormal M-mode: PNEUMOTHORAX

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The Lung Point

Interface of normal lung sliding and absent lung sliding

• Sensitivity: 0.66• Specificity: 1.00

(Lichtenstein 233 ICU pts vs CT)

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Summary: US in pneumothorax

• Outperforms CXR in supine patients• Much higher sensitivity, similar specificity• Lower specificity in critically ill ICU patients• False positives with pleural scarring, TB,

ARDS (specificity 60-91%)• Lung Point: 100% specificity

Summary of Findings in Dyspnea/Hypoxia

Findings Diagnosis

A lines Asthma, COPD, PE

Diffuse B linesCardiogenic

pulmonary edema

Loss of pleural line, consolidation, focal B lines

Pneumonia

A lines without pleural sliding, lung point

Pneumothorax

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Objectives

• Basic principles of lung ultrasound• Key lung ultrasound findings• Brief overview of thoracentesis windows

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Thoracentesis

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US Guidance in Thoracentesis

• Find fluid on ultrasound• Establish landmarks for safe needle insertion

with adequate depth• Usually not done under direct US guidance• Check for lung sliding before AND after the

procedure

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Safe for thoracentesis?

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Safe for thoracentesis?

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