Objectives Basic principles of lung ultrasound Key lung - - PDF document

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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

• r

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

• r

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
• ne LZ

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Clinical Correlation of B-lines

Liteplo et al. Real-time resolution

• f 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,
• ther 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
• rgans)
• 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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Soft Tissue Normal Lung

Beach Ocean

Normal M-mode of Lung

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Soft Tissue

Abnormal Lung

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 lines Cardiogenic 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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