Read this tutorial on the use of point of care ultrasonography (POCUS) for pediatric lung ultrasound. Then test your skills on the ALiEMU course page to receive your PEM POCUS badge worth 2 hours of ALiEMU course credit.
Module Goals
- List indications for performing a pediatric lung point-of-care ultrasound (POCUS).
- Describe the technique for performing lung POCUS.
- Recognize anatomical landmarks and artifacts related to lung POCUS.
- Interpret signs of a consolidation, interstitial fluid, effusion, and pneumothorax on POCUS.
- Describe the limitations of lung POCUS.
Child with Cough and Fever: Case Introduction
A 6-year-old boy presents to the emergency department complaining of cough for 3 days and fever for the last day. His fever was 103°F this morning and he received ibuprofen. He has also had abdominal and back pain. He was seen at the emergency department earlier in the day where he had a chest X-ray 6 hours prior that was interpreted as negative for consolidation and bloodwork including a complete blood count and comprehensive metabolic panel that were within normal limits. He presents with persistent cough and fever and now has increased work of breathing.
On arrival, his vital signs are:
| Vital Sign | Finding |
|---|---|
| Temperature | 99.7 F |
| Heart Rate | 138 bpm |
| Blood Pressure | 102/61 |
| Respiratory Rate | 32 |
| Oxygen Saturation (room air) | 100% |
He is well appearing but has increased work of breathing. His lungs have decreased breath sounds and crackles over the left lung base. No wheezes are appreciated. He has mild subcostal retractions. His abdomen is soft, non-tender, and non-distended. His back is non-tender to palpation. He has normal HEENT, neck, and cardiac examinations, with the exception of tachycardia as above.
Given his presenting signs and symptoms in the setting of a recent chest X-ray that was interpreted as normal, you decide to perform a lung point-of-care ultrasound (POCUS) examination.
Lung POCUS can be performed for a wide range of cardiorespiratory complaints including cough, fever, difficulty breathing, chest pain, hypoxia, and chest trauma. It can also facilitate early diagnosis, allowing for appropriate management. Children are excellent candidates for lung POCUS as they have thinner chest walls and smaller thoracic widths than adults.
Background
The lungs were traditionally considered poorly accessible to ultrasound, as ultrasound waves cannot penetrate air-filled structures; however, lung POCUS relies on the interpretation of patterns of artifacts to evaluate the normal, air-filled lungs.
When there is lung pathology, the consolidation or fluid allows for direct visualization of the pathology with lung POCUS and replaces the air artifacts. Fluid in a consolidation or effusion is easily visualized with ultrasound if the fluid has direct contact with the pleural surface. As lung POCUS will only visualize the lung under the probe, it is essential to completely evaluate the lungs anteriorly, laterally, and posteriorly to avoid missing pathology.
Technique
Positioning and Probe
Figure 1: Younger children can sit in their parent’s lap and give a hug for lateral and posterior lung scanning.
- The patient should be in a position of comfort: supine, sitting, or in parent’s lap (Figure 1).
- Warm gel helps with the child’s comfort.
- Distractions such as a toy, book, or phone/tablet can also help ease anxiety.
- Use a linear high frequency probe. If increased depth is needed, such as in the evaluation for effusion, a curvilinear or phased array probe may also be used.
Scanning Protocols
There are different protocols to scan the lung depending on the purpose of the evaluation. For example, in pneumothorax, we focus on the anterior chest where air rises in a supine patient, and for the extended Focused Assessment with Sonography (eFAST) exam, we focus on more dependent areas where pleural fluid or blood collects. Below we discuss the complete lung exam which is often used in evaluating for pneumonia.
Figure 2: The 6-zone lung scanning protocol includes anterior, lateral, and posterior lung fields bilaterally.
- A 6-zone lung ultrasound protocol is used for a complete lung examination (Figure 2):
- Anterior lungs bilaterally are scanned in the mid-clavicular line from the apex to the base of the lungs and diaphragm.
- Lateral lungs bilaterally are scanned in the mid-axillary line from the apex to the base of the lungs and diaphragm.
- Posterior lungs bilaterally are scanned medial to the scapulae and lateral to the vertebral bodies from the apex to the base of the lungs and diaphragm.
- Place the probe longitudinally, perpendicular to the ribs, with the probe marker towards the patient’s head. Identify anatomical landmarks on ultrasound (Figure 3, Video 1).
Figure 3: Normal lung with A-lines in longitudinal (left) and transverse (right) orientations
Video 1: Normal lung POCUS in longitudinal orientation
Video 2: Normal lung POCUS in transverse orientation
Normal Lung Findings
- Ribs: Hyperechoic, curvilinear structure with posterior acoustic shadowing
-
Pleural line: Hyperechoic line immediately deep to the ribs
- Lung sliding sign: Visceral and parietal pleural are juxtaposed and sliding against each other with respirations, giving the pleural line a shimmering or “ants marching on a log” appearance. For additional examples, see the PEM POCUS Endotracheal Intubation Confirmation article, specifically in Section 2 – Indirect Confirmation: Visualize Bilateral Lung Sliding.
- Lungs filled with air: Visualized on POCUS as horizontal A-lines, which are a reverberation artifact of the pleural line. The pleural line is reflected as the ultrasound beams bounce back and forth between the probe and the highly reflective pleural line, and therefore the distance between A-lines is the same as the distance between the probe and the pleural line (Figure 4).
Figure 4: Reverberation artifact and A-lines. The probe sends out ultrasound waves that bounce back and forth between the highly reflective pleural line and the probe (leftmost 3 arrows). The ultrasound machine then interprets these signals as A-lines equidistant from the pleural line (rightmost 3 arrows).
Figure 5: Pneumonia with sonographic hepatization, air bronchograms, and irregular pleural line
Video 3: Lung POCUS showing a pneumonia
Consolidation will appear as a subpleural, hypoechoic, irregularly shaped area, which will move with respirations. It can have the following findings on lung POCUS:
- Hepatization refers to the homogenous, soft tissue echotexture due to fluid in the lung.
- Shred sign refers to the irregular borders of the non-pleural edge of a pneumonia that is not translobar and thus adjacent to normal lung.
- Pleural line irregularities refer to the hypoechoic or fragmented pleural line at the consolidation.
- Hyperechoic air bronchograms are air in the bronchioles (white dots or branches) surrounded by hypoechoic (dark), fluid-filled lung (Figure 5 and Video 3).
Figure 6: Lung POCUS showing B-lines (A) and a confluence of B-lines, known as the waterfall sign (B)
Video 4: Lung POCUS showing a confluence of B-lines (waterfall sign)
B-lines represent interstitial fluid and may arise from viral infection, pulmonary edema, or acute respiratory distress syndrome (ARDS).
-
POCUS appearance:
- Ring-down artifacts that arise from the pleural line and extend to the bottom of the screen (Figure 6A). They move with lung sliding and erase A-lines at their intersection.
- More than 3 B-lines in an intercostal space has been considered abnormal in the adult population. However it may not always be feasible to accurately count the number of B-lines.
- The distribution of B-lines may help differentiate etiologies, with focal B-lines in pneumonia or atelectasis, and diffuse B-lines in pulmonary edema or ARDS.
- Waterfall sign: A confluence of B-lines (Figure 6B and Video 4)
Figure 7: Lung POCUS with subpleural consolidation
Video 5: Lung POCUS with subpleural consolidation
Subpleural consolidations are small hypoechoic or tissue-like structures with pleural line abnormalities and blurred margins (Figure 7 and Video 5). They measure <1 cm and are usually seen with a viral process.
Figure 8: Pleural effusion with linear probe (A) and phased array probe for increased depth (B).
Video 6: Lung POCUS with pleural effusion using linear probe
A pleural effusion is visualized as anechoic (black) fluid between the chest wall and lung or between the diaphragm and lung (Figure 8 and Video 6).
- Scan the lateral chest in the posterior axillary line in the supine patient, as fluid is dependent and will accumulate posteriorly.
- The pleural effusion can be fluid in an infectious process or blood in the setting of trauma.
Absent Lung Sliding
Video 7: Lung POCUS showing a pneumothorax with absent lung sliding
In pneumothorax, there is air between the visceral and parietal pleural, so there will be no lung sliding visualized on lung POCUS.
- Scan for a pneumothorax in the anterior chest in the 2nd-4th intercostal space in the mid-clavicular line in a supine patient, as air will rise to the highest point in the chest.
- The pleural line will appear as a static, hyperechoic line (Video 7).
- There will be A-lines visualized, but no B-lines.
- Pro Tip: The presence of B-lines is highly sensitive against the presence of a pneumothorax in that location.
Lung Point
Video 8: Lung POCUS with evidence of a lung point
Lung point, when seen, is the edge of the pneumothorax, where regular lung sliding occurs adjacent to absent lung sliding (Video 8).
- Lung point is 100% specific for pneumothorax, but it may not be visualize d for a large pneumothorax with lung collapse.
Motion (M) Mode
Figure 9: Lung POCUS showing a normal lung with the seashore sign (A) and a pneumothorax with the barcode sign (B)
M-mode may also be used to evaluate for pneumothorax.
- Normal lung: There will be the seashore sign, with a granular pattern representing aerated, moving lung below the pleural line (Figure 9a).
- Pneumothorax: There will be a barcode or stratosphere sign, with no aeration or movement below the pleural line (Figure 9b).
Additional examples can be found in the PEM POCUS: Endotracheal Tube Confirmation article in Section 2 – Indirect Confirmation: Visualize Bilateral Lung Sliding.
Figure 10: Lung abscess with adjacent lung consolidation and pleural effusion
Lung abscess may also be evaluated by lung POCUS and will have a hypoechoic fluid collection (Figure 10).
- Consolidated lung and pleural effusion are also commonly seen.
- Lung ultrasound is more accurate than chest X-ray at evaluating lung abscess.
Lung pathology may be missed without a complete lung POCUS scanning protocol, as you will only see pathology located directly under the probe. The lung POCUS is also operator-dependent, and it has a steep learning curve.
False Negative:
- POCUS can’t visualize a centrally located pneumonia not extending to the pleural surface. A lung consolidation needs to extend to the pleural surface to be visualized on lung POCUS.
- However, a study in adult patients showed that 99% of lung consolidations extend to the pleura [1]. Thus, in children with smaller lung mass, most consolidations likely will be detected by lung POCUS.
False Positives:
Left Lower Chest
|
 Figure 11: The spleen and the stomach with air may be misinterpreted as consolidation. |
Thymus
|
 Figure 12: Thymus (*) located adjacent to the heart |
There have been multiple studies of lung POCUS identifying pneumonia in children, and several meta-analyses have been published [2-4]. Table 1 summarizes these studies, showing an overall high accuracy for lung POCUS diagnosis of pneumonia in children.
| Study | N | Sensitivity | Specificity | Comments |
|---|---|---|---|---|
| Pereda et al., Pediatrics 2015 | 8 studies; 765 patients |
96% |
93% |
Evidence supports lung POCUS as an alternative for diagnosis of pneumonia in children. |
| Balk et al., Pediatr Pulmonol 2018 | 12 studies; 1510 patients |
96% |
95% |
Lung POCUS had significantly better sensitivity than chest X-ray, which had a sensitivity of 87%. |
| Tsou et al., Acad Emerg Med 2019 | 25 studies; 3353 patients |
94% |
92% |
Significant difference in accuracy between novice and advanced sonographers. |
Table 1. Meta-analyses of lung POCUS for diagnosis of pneumonia in children
1. Decreased radiation and length of stay
- A randomized controlled trial comparing lung POCUS to chest X-ray for diagnosis of pneumonia showed a 39% reduction in chest X-ray utilization and a decreased emergency department length of stay from 180 to 132 minutes in the patients receiving only lung POCUS with no cases of missed pneumonia [5].
2. Best view for pneumonia
- A study looking at lung consolidation locations in children with pneumonia found that 96% of pneumonias were detected by the transverse view, compared to 86% in the longitudinal view.
- The authors concluded that the transverse orientation detects more pneumonia than the longitudinal view, and that omission of either orientation or any lung zone may miss pneumonia [6].
3. Pneumothorax: POCUS is better
- A meta-analysis of chest X-ray vs ultrasound for diagnosis of pneumothorax showed that ultrasound had a sensitivity of 88% and specificity of 99% compared to sensitivity of 52% and specificity of 100% for chest X-ray. Furthermore, lung POCUS performed specifically by non-radiologist clinicians had a sensitivity of 89% and specificity of 99% [7].
Case Resolution
The patient’s chest X-ray from earlier in the day was interpreted by the pediatric radiologist as negative for consolidation or other pulmonary pathology. You performed a lung POCUS with a linear, high-frequency probe and observed the following:
Video 9: A lung POCUS of the case patient’s left lower lung (affected side)
Though this child with cough, fever, focal lung findings, and respiratory distress had a negative chest X-ray performed 6 hours earlier, your POCUS evaluation identified a left lower lobe pneumonia which helped you make your diagnosis and start the appropriate treatment.
ED Course
The patient received antibiotics for pneumonia. His work of breathing increased during his emergency department visit, and he was started on high flow nasal cannula at 30 L/min with improvement in his respiratory status. He was admitted to the pediatric intensive care unit. He had a repeat chest X-ray 12 hours later that was interpreted by the pediatric radiologist as having new pleural and parenchymal changes in the left hemithorax with questionable pneumonia. He continued antibiotics, and his repeat X-ray 48 hours later showed a clear left lower lobe consolidation with pleural effusion.
Learn More…
References
- Lichtenstein DA, Lascols N, Mezière G, Gepner A. Ultrasound diagnosis of alveolar consolidation in the critically ill. Intensive Care Med. 2004 Feb;30(2):276-281. PMID: 14722643
- Pereda MA, Chavez MA, Hooper-Miele CC, et al. Lung ultrasound for the diagnosis of pneumonia in children: a meta-analysis. Pediatrics. 2015 Apr;135(4):714-22. PMID: 25780071
- Balk DS, Lee C, Schafer J, et al. Lung ultrasound compared to chest X-ray for diagnosis of pediatric pneumonia: A meta-analysis. Pediatr Pulmonol. 2018 Aug;53(8):1130-1139. PMID: 29696826
- Tsou PY, Chen KP, Wang YH, et al. Diagnostic Accuracy of Lung Ultrasound Performed by Novice Versus Advanced Sonographers for Pneumonia in Children: A Systematic Review and Meta-analysis. Acad Emerg Med. 2019 Sep;26(9):1074-1088. PMID: 31211896
- Jones BP, Tay ET, Elikashvili I, et al. Feasibility and Safety of Substituting Lung Ultrasonography for Chest Radiography When Diagnosing Pneumonia in Children: A Randomized Controlled Trial. Chest. 2016 Jul;150(1):131-8. PMID: 26923626
- Milliner BHA, Tsung JW. Lung Consolidation Locations for Optimal Lung Ultrasound Scanning in Diagnosing Pediatric Pneumonia. J Ultrasound Med. 2017 Nov;36(11):2325-2328. PMID: 28586113
- Ding W, Shen Y, Yang J, He X, Zhang M. Diagnosis of pneumothorax by radiography and ultrasonography: a meta-analysis. Chest. 2011 Oct;140(4):859-866. PMID: 21546439
Additional Reading
- Rizvi MB, Rabiner JE. Pediatric Point-of-Care Lung Ultrasonography: A Narrative Review. West J Emerg Med. 2022 Jun 5;23(4):497-504. PMID: 35980421
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