Lung POCUS (Doniger Textbook)

Question 1

Why is lung POCUS more sensitive than xray for diagnosing pneumothorax?

Answer 1

Usually these are sick patients: chest radiographs are especially inaccurate in a supine patient since air layering anteriorly is difficult to detect -one study showed that ultrasound was superior to chest radiographs in identifying traumatic pneumothoraces: sensitivity of 98.1% and specificity of 99.2% compared with chest radiographs (sensitivity of 75.5% and specficity of 100%)

Question 2

What are the 4 point of care questions you can answer via lung POCUS?

Answer 2

1. Is a pneumothorax present? 2. Is a pleural effusion present? 3. Are A-lines or B-lines present? 4. Was endotracheal intubation successful?

Question 3

Which transducer should be used for lung POCUS?

Answer 3

Convex or linear can be used -however, most of the pediatric literature has described lung ultrasound with linear transducers and linear transducers offer the best resolution

Question 4

Why is lung ultrasound particularly different from all other ultrasound examinations?

Answer 4

It’s because lung ultrasound is not based on the anatomic representation of the organ itself but on the ARTIFACTS generated by the lung!

Question 5

What is the best position to assess for the following in a patient: -pneumothorax -pleural effusion

Answer 5

Pneumothorax = supine position (since air rises anteriorly) Pleural effusion = upright/seated position since the fluid accumulates inferiorly/posteriorly

Question 6

Where are the two areas on the chest wall to place your probe in doing a SCREENING lung ultrasound?

Answer 6

1. Anterior chest wall - mid clavicular line at 4th IC space = tells you about pneumothorax (since air rises in a supine patient) 2. Costophrenic recess (ie. LUQ and RUQ) = posteriolateral scan to rule out hemothorax or pleural effusion (since fluid flows to dependent regions)

Question 7

How can you identify the pleural line within the chest wall?

Answer 7

Pleural line = hyperechoic line immediately deep to the ribs (ie. use the ribs as a visual reference point to finding the pleural line)

Question 8

Where should the probe indicator be when you are scanning the lung?

Answer 8

Towards the patient’s head! -remember that the indicator should either always be pointing towards the patient’s head or towards the patient’s right depending on whether you are holding the probe transverse or longitudinal to the body -when scanning the lung, the probe is held longitudinal to the body

Question 9

What is the “bat sign” in lung ultrasound?

Answer 9

Image formed by two ribbs with the pleural line in between them = resembles a bat with open wings.

Question 11

What is lung sliding?

-what does absence of lung sliding mean?

Answer 11

Lung sliding = movement between the visceral pleura and parietal pleura

• should see a to and fro movement synchronized with the respiratory cycle
• absence of lung sliding = pneumothorax or improper endotracheal intubation

Question 12

What is the seashore sign on M mode of lung ultrasound?

Answer 12

Seashore sign: non-moving chest wall appears as horizontal lines (ocean waves) and the sparkling artifact from lung sliding (ie. pleural movement) appears as a grainy pattern (sandy beach)

-demonstrates that the visceral pleura slides directly on the parietal pleura!

Question 13

What is the stratosphere/barcode sign on M mode in lung ultrasound?

Answer 13

Classic sign seen with pneumothorax (aka Barcode sign)

• ultrasound beam hits the free air directly beneath the parietal pleura after traversing the chest wall and is immediately reflected back to the transducer without any scatter caused by the underlying alveolar structure
• thus, there is NO lung sliding and the pneumothorax disrupts the normal sparkling artifact generated by the alveoli
• all the artifact deep to the pleura will be static
• thus you ONLY see horizontal lines and no grainy sand like you should see in a normal lung with the seashore sign

Question 14

Compare and contrast the seashore sign vs. the stratosphere sign?

Answer 14

Seashore sign = on M mode, reflects normal lung sliding = the waves are the non-moving ribs/muscle/chest wall and the sandy beach are the artifacts generated by the movement of the pleura

Stratosphere sign: absence of pleural contact with the lung = the artifact is static thus you see only horizontal lines instead of the sandy beach pattern

Question 15

What is the “lung pulse”?

Answer 15

In the non-ventilated lung (ie. mainstem intubation, apnea, complete atelectasis), the visceral pleura will still present with a tiny rhythmic movement synchronous with the cardiac cycle caused by the arterial pulse and movement of the heart itself

• this can be seen as tiny to and fro movements visually identical to lung sliding but is very short and rapid.
• the presence of this “lung pulse” means that there is pleural contact (ie. no pneumothorax) BUT there is no pulmonary expansion.
• on M mode, will see striped seashore pattern

Question 16

What are “A lines”?

Answer 16

Horizontal lines parallel to the pleural line = reverberation artifact of the ultrasound beam between the pleural and the transducer

-A lines are generated by the presence of air in normal lung parenchyma but will also be present in aerated pathologic conditions like pneumothorax or mainstem intubation

Question 17

What are “B lines”?

-suggestive of what conditions? (6)

Answer 17

B lines = reverberation artifacts like a light beam = are generated when there is a pathologic process that causes thickening of lung and/or partial filling of alveoli by fluid

• B lines arise from the pleural line, move with the pleura during the respiratory cycle, reach the edges of the screen without fading, and are well defined laser like hyperechoic lines
• they also erase A lines
• highly sensitive for any interstitial process such as ARDS, RDS, TTN, cardiogenic pulmonary edema, interstitial pneumonias, pulmonary contusions

Question 18

What 3 things should you look for on M-mode when doing a lung ultrasound?

Answer 18

M mode: generates an image deep to the pleural line = reflection artifact

1. Seashore sign
2. Stratosphere sign
3. Lung pulse

Question 20

What are “C lines”?

Answer 20

C lines = consolidations = these are not actually artifacts but are soft tissue like regions in direct contact with the visceral pleura

-air bronchograms can usually be seen within these consolidations

Question 26

What is a normal amount of B lines to have in a normal lung?

-what number of B lines should concern you for pathologic lung conditions?

Answer 26

It is normal to have a few isolated B lines in the normal lung, especially at lung bases

-however, if you see the presence of more than THREE B line artifacts that are simultaneously visible on an intercostal scan, this should be considered pathologic for ARDS, RDS, TTN, cardiogenic pulmonary edema, interstitial pneumonia, or pulmonary contusion

Question 27

What sonographic artifacts should you expect to see on lung ultrasound in the following conditions:

• normal lung
• pneumothorax
• interstitial syndromes/edema
• pneumonia/atelectasis
• pleural effusion

Answer 27

• Normal lung: A lines with lung sliding
• Pneumothorax: Pure A-lines, no lung sliding
• Interstitial syndromes/edema: B lines only (from increased water content in an aerated lung)
• pneumonia/atelectasis: C-lines (consolidation) (from water-filled parenchyma)
• pleural effusion: No A lines, B lines or C lines (from water only, no parenchyma)

Question 29

Fill in the blank: the presence of ______ on lung ultrasound excludes a pneumothorax.

Answer 29

Lung sliding!

***When scanning the left lung, do NOT confuse cardiac movement for lung sliding (ie. lung movement secondary to cardiac movement is known as the lung pulse)

Question 30

How can you ensure that the vertical artifacts you’re seeing on a lung ultrasound are truly B lines? (4)

Answer 30

1. B lines are multiple hyperechoic well-defined vertical lines which START on the pleural line
2. They move with lung sliding
3. They reach the edge of the bottom of the screen
4. They erase the A lines

Question 31

What are the vertical artifacts seen with subcutaneous emphysema?

-how can you differentiate them from B lines?

Answer 31

E-lines and W-lines = very similar to B lines but they are STATIC (don’t move with lung sliding) and are generated in the chest wall, not the pleural line

Question 32

How can you ensure that you’re looking at the pleural line and not soft tissue or subcutaneous emphysema?

Answer 32

The pleural line should be immediately deep to the ribs!!! So use the ribs as a reference to identify the pleural line.

-any hyperechoic lines ABOVE the ribs (dynamic or static) are not in the pleural cavity but is the soft tissue/chest wall

Question 33

What are two ways to confirm endotracheal tube placement after an intubation?

-which has more evidence to support it right now?

Answer 33

1. Sonographic visualization of the tube in the trachea: less evidence right now
2. Evaluation of bilateral lung expansion during manual ventilation
   - look for lung sliding bilaterally: put the probe onto the anterior chest and scan bilaterally
   - lung sliding synchronized to the manual ventilations must be seen on both sides
   - advantage of this approach = can detect a mainstem intubation and guiding its correction

Question 34

You have just intubated a patient. You would like to confirm endotracheal placement via ultrasound. You place the linear probe onto the anterior chest bilaterally and you see lung sliding on the right but a lung pulse on the left. What does this tell you? What do you do?

Answer 34

This tells us that the lung on the left side is not being ventilated and you most likely have a right mainstem intubation. Thus, can gently pull the tube back little by little under direct visualization of the left lung until lung sliding is detected

-remember that the cause of non-expansion of the left lung can be something other than a mainstem intubation (ie. bronchial foreign body or mucus plugging)

Question 35

You have just intubated a patient. You would like to confirm endotracheal placement via ultrasound. You place the linear probe onto the anterior chest bilaterally and you see lung sliding on the right but no lung sliding or lung pulse on the left. What does this tell you? What do you do?

Answer 35

Absence of lung pulse AND lung sliding tells you that there is no lung expansion at all. Thus, you should be very concerned for pneumothorax! Consider needle decompression

Question 36

What are 3 sonographic signs of pneumothorax?

Answer 36

1. Absence of lung sliding
2. Presence of lung points
3. Absolute absence of B lines

***Any of the following indicates a pneumothorax (remember that a normal person may have complete absence of B lines…but if there is any B line present, then this excludes a pneumothorax, even in the absence of lung sliding since B lines are generated with direct pleural contact)

Question 37

What is the sensitivity of the presence of lung sliding on lung ultrasound to exclude pneumothorax?

-what is the specificity of absence of lung sliding for pneumothorax?

Answer 37

Almost 100%

-ie. one single examination of the highest spot on the chest showing lung sliding is enough to exclude a pneumothorax

***Specificity of absence of lung sliding for pneumothorax: only 60-90% specific

-other things can cause absence of lung sliding: anything else that can cause non-expansion of the lung such as pleural adhesions (rare in peds), pulmonary emphysema

Question 38

What is the most common cause of absent lung sliding in adults?

Answer 38

Pulmonary emphysema!

Question 39

What sonographic sign is 100% specific for pneumothorax?

Answer 39

The lung point!!!!

• sensitivity is not as high but as a general rule, it will only be absent in cinically evidence pneumothoraces (ie. tension pneumothorax)
• lung point: transition line where the collapsed lung loses contact with the chest wall
• this is the line where visceral pleura detaches from parietal pleura, glides on the chest wall during the respiratory cycle, accompanying residual expansion of the collapsed lung
• if the transducer is placed exactly on this line, you may see an alternation of lung sliding and absence of lung sliding synchronous with the respiratory movement
• essentially, the point where you see both lung sliding and absence of lung sliding = where pneumothorax begins

Question 40

What is the next step once you detect absence of lung sliding on lung ultrasound?

Answer 40

Next try to find the lung point!

• place the transducer on the posterolateral wall
• this is the spot where pleural contact will be detected in a partial pneumothorax since lung is heavier than free air and wil be seen posterio-laterally
• if no lung sliding is present at this point, there wil be no detectable lung point and your diagnosis is a complete pneumothorax OR another process (ie. pleural adhesion)
• if lung sliding is found at the posterolateral wall, slowly slide the transducer back towards the anterior wall looking for the point where lung sliding becomes absent
• this is the lung point!!!!
• represents the margin of the pneumothorax and can be used to monitor the size

Question 41

Where is the first place to accumulate fluid in a pleural effusion on ultrasound?

Answer 41

Posterior/inferior region (posterior costophrenic sinus)

-will see an anechoic layer overlying pulmonary parenchyma

Question 42

What are 3 signs you may see on lung ultrasound in a patient with pleural effusion?

Answer 42

1. Accumulation of fluid overlying the pulmonary parenchyma = anechoic layer
2. Absent lung sliding
3. Pulmonary parenchyma will present varying degrees of aeration, depending on the volume of effusion and the compression caused by it

Question 43

How can you differentiate between transudative vs. exudative (empyema) pleural effusions on ultrasound?

-what will you see with a traumatic hemothorax?

Answer 43

Transudative/hemothorax: seen as purely anechoic fluid (may see soft tissue like clots in hemothorax)

• empyema: see floating particles, organized fibers and septations
• traumatic hemothorax: will see swirling hyperechoic particles (air bubbles) with an associated pneumothorax

Question 44

What is more sensitive/specific for a pneumonia: ultrasound or CXR?

Answer 44

Ultrasound! Sensitivity and specificity of about 90%

Question 45

What do pneumonic consolidations look like on lung ultrasound?

Answer 45

Subpleural hypoechoic soft tissue like mass of variable size and shape

• can have poorly defined borders and can be surrounded by B lines
• the surrounding B lines are useful in differentiating pneumonias/atelectasis from other types of consolidation
• in beginning of pneumonia, can see C-lines which are multiple, sall (< 1 cm) horizontal lines under the pleura among a region of B lines (Vertical lines)

Question 46

How can you differentiate between pneumonia vs. atelectasis on lung ultrasound?

Answer 46

Look for DYNAMIC air bronchograms vs. STATIC air bronchograms

• also look for “Hepatization” of the lung = dense consolidation above the diaphragm that looks similar to the echotexture of the liver
• Pneumonias: alveolar process that floods the larger airways with secretions and thus the airflow causes the secretions to move back and forth in the bronchi. This movement of secretions = DYNAMIC AIR BRONCHOGRAM SIGN! This is pathognomonic for pneumonia
• also see a tree like branching pattern
• Atelectasis: get occluded airways and thus get STATIC AIR BRONCHOGRAMS = no airflow and thus no movement of secretions inside the bronchi
• get bronchovascular structures closer together tending to a parallel pattern

Question 47

Name the following ultrasound finding in this image:

Answer 47

Hepatization of the lung = seen in pneumonia!

Question 48

In a patient with cardiogenic pulmonary edema, what specific ultrasound sign are you looking for when you scan the lungs?

Answer 48

B lines!! = extravascular water (ie. interstitial edema)

-the absence of B lines excludes the possibility of a cardiogenic pulmonary edema with a sensitivity of 100%

Question 49

What is the “white lung” sonographic sign?

Answer 49

In severe pulmonary edema, B lines are so numerous that they merge together and generate “white lung” which is the same as “ground glass” appearance on CT scan