Thanks to Daniela Villegas Martinez for the filming of the performance of the live lung ultrasound! A special thanks to Dr Maria Fraga from Children's Hospital of Philadelphia (co-PI of the PuRPOSE Study) for reviewing the content and providing guidance for the preparation, orchestration and content review.  Thanks to Florence and her family for accepting to be part of the filming!

Lung Ultrasound Score

Scoring system from: "Brat, R., Yousef, N., Klifa, R., Reynaud, S., Aguilera, S. S., & De Luca, D. (2015). Lung ultrasonography score to evaluate oxygenation and surfactant need in neonates treated with continuous positive airway pressure. JAMA pediatrics, 169(8), e151797-e151797."

Pneumothorax

Orientation of the linear probe on the chest of the newborn

Lung Ultrasound in the NICU - Review

What is Neonatal Lung Ultrasound?

Neonatal lung ultrasound is a point-of-care ultrasound (POCUS) modality used in the Neonatal Intensive Care Unit (NICU). It is portable, readily available in the unit, non-invasive, and does not involve radiation. It offers descriptive applications, allowing for diagnosis and guidance during procedures and recruitment methods. However, it has limitations, including being operator-dependent, limited in evaluating deep pathology (missing pneumonia not close to the surface), and requiring access to a machine and quality assurance. Skill in neonatal lung ultrasound is not routinely taught enough in neonatology training.

Probes and Technique

• Preferred Probe: The linear probe (often referred to as a hockey stick probe in some contexts) is the best probe for lung ultrasound. Other probes like the phased array (good for cardiac/cranial) and curvilinear (abdomen) exist, but the linear probe's very high frequency provides high resolution at a peripheral depth, which is excellent for looking at artifacts around the plural line. While probes can be used interchangeably if only one is available, knowing the best probe for a task is beneficial.

• Focus on Artifacts: Unlike looking at the actual architecture of the organ as in CAT scans or abdominal ultrasound, lung ultrasound involves interpreting normal and abnormal artifacts.

• Avoiding Filters: On ultrasound machines, it is important to avoid using any filtering effects (like the xres button on Philips apparatus), as this filters artifacts, and for lung ultrasound, you want to generate these artifacts.

• Probe Orientation: When scanning, the probe is typically positioned longitudinally, with the tip of the hockey stick pointing towards the head (12 o'clock or cranial). This means the left side of the screen represents the cranial portion, and the right side represents the caudal portion (towards the feet).

• Scanning Protocol (Zones): The chest is divided into zones for scanning. One technique involves using three zones on each side: Zone one and two anterior, and zone three lateral. Another description divides the chest into six zones: Right upper, right lower, and right lateral, and left upper, left lower, and left lateral.

  • Scanning is done along landmarks:

    • Upper Zones: Along the mid-clavicular line, scanning from the clavicle to the nipple line.

    • Lower Zones: Along the mid-clavicular line, scanning from the nipple line down to the coastal margin or diaphragm.

    • Lateral Zones: Along the mid-axillary line, scanning from the axilla down to the coastal margin or diaphragm.

• Image Acquisition: One clip per lung zone is typically needed, along with one M-mode per lung zone to evaluate for presence of pneumothorax. Clips should be set to record for at least 3 to 5 seconds to capture breathing patterns.

Key Findings and Artifacts

Understanding the artifacts is crucial for interpreting neonatal lung ultrasound:

• Subcutaneous Tissue: Appears at the top of the 2D picture. In M-mode, it's represented as a static area at the top.

• Ribs: Appear below the subcutaneous tissue. They can look anechoic or hyperechoic depending on the angle. When scanning cross-sectionally, they appear as big circles. They create acoustic shadowing (black area behind the ribs) because the ultrasound beam hits the bone and cannot penetrate through.

• Plural Line: One of the most important findings. It represents the visceral and parietal pleura together. It is a highly reflective surface and appears bright or hyperechoic.

  • Normal Plural Line: Thin or smooth.

  • Abnormal Plural Line: Very dense, jagged, or thickened.

• A-lines: A normal finding in lung ultrasound. They represent the reverberation artifact from the highly reflective plural line.

• B-lines: An abnormal finding in lung ultrasound, representing edema, intralobar atelectasis, or fibrotic changes.

  • Appear as lines coming vertically down from the plural line.

  • Can be normal in neonates right after birth due to fluid-filled lungs.

  • Coalesced B-lines are a more significant abnormal finding.

  • More than three B-lines in a space indicate a more pathologic lung (later after birth).

• Lung Sliding: A normal finding where the visceral and parietal pleura move against one another with respiration.

  • 2D Visualization: Can be seen as movement back and forth of the plural line or B-lines in a fanning position or like little white dots ("Ants Marching").

  • M-mode Visualization: Creates a "Seashore sign", where there is a static area at the top (subcutaneous tissue/ribs), a bright line (pleural line), and then a granular/sandy pattern below representing the movement of the lung ("waves").

• Absent Lung Sliding: An abnormal finding where the visceral and parietal pleura are separated, typically by air (pneumothorax).

  • 2D Visualization: Lack of the fanning movement or "Ants Marching".

  • M-mode Visualization: Creates a "Barcode sign" or "Stratosphere sign", appearing as static horizontal lines going all the way down because the ultrasound beams cannot get through the air to see the lung movement.

• Plural Effusion: Accumulation of fluid in the pleural space.

  • Appears black on lung ultrasound.

  • On chest x-ray, fluid appears white, but not everything white on an x-ray is an effusion.

  • Can cause collapse or atelectasis of the lung, which may be seen floating or flapping within the fluid. The wiggling apex of a collapsed lung in fluid is called a "Squid sign".

  • Septations can be present within an effusion, appearing as hyper-echoic lines.

• Atelectasis/Consolidation: Collapse or solidification of lung tissue.

  • Intralobar atelectasis can be represented by B-lines.

  • Can be seen as a collapsed lung, sometimes pushed over by other pathology.

  • A collapsed lung pulsating with the heart beat is called a "Lung pulse".

  • Distinguishing atelectasis from pneumonia based on dynamic vs. static air bronchograms is reported in literature but is very difficult in practice and should be used with clinical experience.

Clinical Applications

Lung ultrasound in the NICU has numerous applications:

• Diagnosis:

  • Distinguish Respiratory Distress Syndrome (RDS) vs. Transient Tachypnea of the Newborn (TTN).

  • Detect pneumothoraces.

  • Detect plural effusions.

  • Evaluate pulmonary edema.

  • Detect anesthesia-induced atelectasis.

  • Distinguish chronic lung disease (thickened pleura).

  • Identify homogeneous lung disease like heart failure (homogeneous B-lines).

  • Identify atelectasis and consolidation (with caution regarding air bronchograms).

• Procedural Guidance:

  • Guide thoracentesis (drainage of pleural fluid). This can be done statically (finding the best location) or dynamically (guiding the needle in real time). Static guidance is often preferred for chest tube placement for pneumothorax or effusion.

  • Guide Endotracheal Tube (ET) position (although this is an emerging application and can be quite challanging).

  • Ensure you know what you are targeting before any chest instrumentation (needle or chest tube) to avoid misplacing it into other structures like the heart or collapsed lung when fluid is not present.

• Functional and Predictive Applications:

  • Using a Quantitative Lung Ultrasound Score. One method involves scoring three zones (anterior zones 1 & 2, lateral zone 3) on each side from 0 to 3 (0=no B-lines, 1=some B-lines, 2=many B-lines (>3-5), 3=large subplural consolidations).

  • Differentiate RDS and TTN using the score.

  • Predict the development of Bronchopulmonary Dysplasia (BPD) at 10 and 14 days of life.

  • Assess readiness to wean from CPAP or for extubation.

  • Guide diuretic therapy.

  • Guide optimal Positive End-Expiratory Pressure (PEEP) and recruitment methods.

• Changing Clinical Management: Lung ultrasound at the bedside can significantly alter clinical decisions, such as correctly diagnosing tension pneumothorax vs. effusion, and guiding appropriate interventions.

• Resuscitation: Can be used during resuscitations to guide volume replacement therapy, surfactant administration, and ventilatory strategies.

Guidelines and Education

• Guidelines now exist for using point-of-care ultrasound for lung in neonates, including from the American Academy of Pediatrics (AAP), which published a guideline table in 2022 calling for education and operationalization of ultrasound in the NICU. These guidelines provide algorithms for interpreting findings like B-lines, A-lines, lung sliding, and M-mode patterns to differentiate conditions depending on whether the ultrasound is done right after birth or later.

• Despite its many applications and relative ease of teaching, the skill is not routinely taught enough in neonatology training, highlighting a need for increased education.

Research Context

Lung ultrasound is also used in research projects, such as a partnership involving Children's Hospital of Philadelphia (CHOP) and the MCH (likely Montreal Children's Hospital based on context) for the Purpose study involving congenital diaphragmatic hernia (CDH) patients. This study has specific protocols for lung ultrasound acquisition, including anonymization requirements, placing study IDs (differing slightly between sites), using specific presets, and the exact zones and types of images/videos (clips and M-modes) required at different time points (delivery room, 12 hours, pre-extubation). For CDH patients, initial scans for the study are typically on the contralateral side of the defect, while pre-extubation scans involve all six zones.

Pleural Effusions

Module on effusions can be found on this part of the website.

Bilateral pleural effusions in the subxyphoid view.

Other resources

Other great resources regarding neonatal lung ultrasound can be found on this NICUPocus webpage.

Lung Ultrasound Made Easy