Respiratory Systems 17 - Thoracic Ultrasound

Question 1

Briefly describe the principles of ultrasound

Answer 1

• High frequency sound waves are bounced off internal aging of organs and tissues
• This produces 2D images
• May be B mode or M mode

Question 2

Why is the choice of ultrasound probe important?

Answer 2

• A 3.2MHz probe is rounded, so it can get between ribs, and it creates a low resolution image with high depth of view
• 7-12MHz probes have a flat edge, they produce high resolution images with lower depth of view, used to examine under the surface of the skin

Question 3

What appears as an echogenic line in an ultrasound?

Answer 3

• Visceral and parietal pleura

- Diaphragm

Question 4

What are the signs of a healthy lung on B type ultrasound?

Answer 4

• Gliding pleura, where you can see the visceral pleura moving over the parietal pleura during breathing
• A lines (horizontal)
• B lines (perpendicular to pleura, caused by the interlobular septa)

Question 5

What are interlobular septa?

Answer 5

The boundaries between secondary pulmonary lobules

Question 6

What is an M mode ultrasound?

Answer 6

• A display of motion in the lung

- Echoproducing interfaces are displayed against time

Question 7

What is the sign of a normal lung using M mode ultrasound?

Answer 7

• Sea shore sign
• Above the long is horizontal lines, like the sea
• The lung has a grainy appearance
• Used to determine if there is pneumothorax

Question 8

What planes are usually used in ultrasound?

Answer 8

• Axial or transverse plane allows the liver to be viewed
• Longitudinal/coronal plane allows the lung border to be established in large patients
• Paracoronal plane is along the IC space on the side of the body, this eliminates the rib
• Longitudinal plane

Question 9

List the main uses of ultrasound of the thorax

Answer 9

• Detect pleural effusion and guide drainage
• Differentiate sub-pulmonary from sub-phrenic fluid
• Assess tumour invasion
• Guide pleural and lung biopsy
• Identify pneumothorax
• Assess respiratory muscle function

Question 10

What colour is fluid on ultrasound?

Answer 10

Black

Question 11

In inspiration, what causes the ribs to elevate and the sternum to move anteriorly?

Answer 11

• Scalenes and sterno-clavicular muscle

- External intercostal muscles elevate ribs

Question 12

How is function of the phrenic nerve assessed?

Answer 12

• Forces inspiration (a sniff)
• Normally there is rapid caudal movement
• If abnormal, there is paradoxical cranial movement