DR SURESH A

ASSOCIATE PROFESSOR

DEPARTMENT OF RADIOLOGY

VIMS& RC

SONOGRAPHIC DIAGNOSIS OF

PNEUMOTHORAX

INTRODUCTION

• Thoracic sonography is a rapidly evolving imaging

modality of choice for lung imaging.

• Lung sonography is made possible by the interpretation

of ultrasound artifacts, caused secondary to

confinement of air between the lung and chest wall,

that prevents diffusion of the ultrasound beam into the

parietal pleura and deep lung structures.

• Bedside ultrasound of the lung has an established role

in the diagnosis of thoracic diseases.

PROBE SELECTION

• Linear array high frequency probe

(5-13 MHz) To analyze

superficial structures such as the

pleural line and providing better

resolution.

• Curvilinear array probe (1-8 MHz)

More suitable in imaging deeper

lung structures as it provides better

penetration at the cost of less

resolution.

• Phased array probe (2-8 MHz)

Flat and smaller footprint is better

suited for imaging between the ribs;

commonly used in cardiac imaging.

TECHNIQUE• Patients are scanned in

supine/Erect position.

• The probe is placed in sagittal position on the anterior chest wall – 2nd intercostal space in the mid-clavicular line

• The sonographer should identify the landmarks of two ribs with posterior shadowing behind them and visualize the plaueral line in between them Bat Sign

• Periosteum of ribs represent the wings and the hyperechoic pleural line between represent the bats body

• In between the two ribs, the two pleural layers are seen sliding across. BAT SIGN

TECHNIQUE

• Pneumothorax contains air and no fluid, hence it will rise to the anterior and least dependent area of the chest.

• As the patients are commonly supine, this area corresponds to the anterior region of the chest at the 2nd to 4th intercostal spaces in the mid-clavicular line.

• Hence, this is the recommended initial area for investigation in trauma cases

• If the patient is upright, air accumulates in apicolateral location

SAGITTAL SCAN DEPICTING NORMAL ANATOMY

PNEUMOTHORAX

• Pneumothorax: refers to the presence of gas (air) in the pleural space.

• It is useful to divide pneumothoraces into three categories

1)Primary spontaneous: No underlying lung disease

2)Secondary spontaneous: Underlying lung disease is present

3)Iatrogenic/traumatic

Traumatic - Commonly associated with both blunt and penetrating chest injuries.

CHEST ULTRASOUND TIPS

• First get oriented to the machine

• Next get oriented to the patient

• Find something that you recognize (it probably wont be the lung at first)

• Navigate from there Confirm normal findings

• Seek and explore abnormal findings

ADVANTAGES OF ULTRASOUND

• Performed at bedside without delays

• No radiation or contrast exposure

• Repeatable with serial assessment

• Detects and localizes pathology

• Guides procedures

DISADVANTAGES OF ULTRASOUND

• Operator dependent

• Confusing artefacts

• Training requirements

NORMAL LUNG FINDINGS IN THORACIC

ULTRASOUND

• BATWING SIGN

• PLEURAL LINE

• SLIDING LUNG

• A LINES AND B LINES

• LUNG PULSE

• POWER/ DOPPLER SLIDE SIGN

• PLEURAL LINE/SLIDING SIGN: Most important finding in normal aerated lung

• Sonographer visualizes the hyperechoic pleural line in between two ribs moving back and forth

• Lung sliding corresponds to the to and fro movement of the visceral pleural on the parietal pleura occuring with respiration.

• Two different patterns are displayed: motionless portion above the pleural line – Horizontal waves

• Sliding below the pleural line – granular pattern (sand) in M mode.

• The resulting picture resembles waves crashing onto the sand – Seashore sign (indicating normal aerated lung)

BAT WING SIGN

PLEURAL LINE/SLIDING SIGN

SEA SHORE SIGN (M MODE)

• B-LINES OR COMET-TAIL ARTIFACTS: are reverberation artifacts

appearing as hyper echoic vertical lines that extend from the pleura to

the edge of the screen.

• Comet-tail artifacts move with lung sliding and respiratory movements

• These artifacts are seen in normal lung due to acoustic impedance

differences between the water and air

• Excessive “B-lines” on the other hand may be abnormal – indicating

interstitial edema

A-LINES

A-lines are a type of reverberation artifact, equally

spaced, horizontal lines originating from the hyperechoic

pleural line.

In normal lung, B-lines extend out and erase the “A-lines”

LUNG PULSE

POWER SLIDE

• It refers to the use of power Doppler to help identify lung

sliding. Power Doppler helps pick up subtle flow and

movement.

• If lung sliding is present, power Doppler will light up the

sliding pleural line with color flow.

LUNG FINDINGS IN PNEUMOTHORAX

• ABSENT LUNG SLIDING SIGN

• LOSS OF COMET-TAIL ARTIFACTS

• BROADENING OF THE PLEURAL LINE TO A BAND

• LUNG POINT OR TRANSITION POINT

• CHANGE FROM SEASHORE TO (STRATOSPHERE OR BAR CODE SIGN IN M MODE)

LUNG SLIDING SIGN

• Presence of sliding effectively rules out pneumothorax.

• The absence of lung sliding does not necessarily

indicate that a pneumothorax is present.

• Lung sliding can also be abolished in other conditions

like acute respiratory distress syndrome, pulmonary

fibrosis, large consolidations, pleural adhesions,

atelectasis, right main stem bronchus intubation,

phrenic nerve paralysis

LUNG POINT IN PNEUMOTHORAX

Pneumothorax

Lung point

LUNG POINT DEMONSTRATED ON CT AND ON ULTRASOUND

EVALUATION OF PNEUMOTHORAX BY M-MODE

SEA SHORE SIGN BAR CODE SIGN

COMET TAIL ARTIFACTS / B-LINES

• In pneumothorax, ultrasound demonstrates the loss of “comet

tail artifacts.

• These artifacts are lost due to air accumulating within the

pleural space causing reduction in the propagation of sound

waves and eliminating the acoustic impedance gradient.

• As comet tail artifacts are generated by the visceral pleura, and

this pleura is not visualized in a pneumothorax, the artifacts are

not generated.

• The visualization of even one comet-tail essentially rules out the

diagnosis of a pneumothorax

A-LINES

• “A-lines” are thoracic artifacts that help in the diagnosis of pneumothorax.

• The space between each A-line corresponds to the same distance between the skin surface and the parietal pleura.

• In the normal patient, B lines extend from the pleural line and erase the A lines

• “A-lines” will be present in a patient with pneumothorax but “B -lines” will not be seen.

• If lung sliding is absent with the presence of “A-lines” the sensitivity and specificity for occult pneumothorax is 95 and 94 % respectively

LUNG-POINT SIGN

• Lung-point sign – occurs at the border of a pneumothorax.

• Helpful in determining the actual size of the pneumothorax

• This sign can be delineated using M-mode where alternating “seashore” and “stratosphere” patterns are depicted over time

• “lung-point sign” is 100% specific for pneumothorax and defines its border

• If the lung-point sign is identified in a location more posterior or lateral, the larger the pneumothorax.

• The determination of the size of a pneumothorax is important, as larger pneumothoraces are likely to require thoracostomy.

LUNG PULSE

• Rhythmic movement of the pleura in

synchrony with the cardiac rhythm.

• Best viewed in areas of the lung adjacent

• to the heart – at the pleural line.

• A result of cardiac vibrations transmitted to

the lung pleura in poorly aerated lung

• Cardiac activity is essentially detected at the

pleural line – when there is absent lung

sliding in certain conditions.

ALGORITHM FOR THE ULTRASOUND DIAGNOSIS

OF PNEUMOTHORAX

CONCLUSION

• Thoracic sonography of has become a well-established modality in the

acute care setting for detection of pneumothorax.

• It is Indispensable in the blunt or penetrating chest trauma patient

• USG chest and AP radiograph are complementary to eachother in

diagnosing a pneumothorax.

• CT scan remains the gold standard and may still catch smaller occult

pneumothoraces that ultrasound misses.