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 Table of Contents  
REVIEW ARTICLE
Year : 2022  |  Volume : 11  |  Issue : 2  |  Page : 117-123

The neonatal lung ultrasound – What should i know as a neonatologist?


Department of Neonatology, Manipal Hospital, Bengaluru, Karnataka, India

Date of Submission22-Dec-2021
Date of Decision01-Feb-2022
Date of Acceptance06-Feb-2022
Date of Web Publication20-Apr-2022

Correspondence Address:
A Venkatesh Harohalli
Manipal Hospital, Bengaluru, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jcn.jcn_144_21

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  Abstract 


The point-of-care lung ultrasound has been used in the care of sick neonates. With the nonionizing radiation property, portability, repeatability, and quick availability, the ultrasound has taken a big role in the management of neonates with respiratory diseases. The clinician taking care of the sick neonate should be well experienced in performing the ultrasound of the lung. The pleura is the main source of information about lung pathology under ultrasound. This guides the ultrasound in making the diagnosis. The utility of ultrasound in neonatal intensive care includes the common pathological conditions of the lung–respiratory distress syndrome, transient tachypnea of newborn, meconium aspiration syndrome, pneumonia pleural effusion, and emergency conditions such as pneumothorax. The knowledge about the normal lung ultrasound, the lung pathology, and its correlation with the lung ultrasound is essential in making the diagnosis. The review article is focused to answer all the aforementioned.

Keywords: Lung, neonate, pleura, ultrasound


How to cite this article:
Harohalli A V, Anitha Raju N M, Narayanaswamy V. The neonatal lung ultrasound – What should i know as a neonatologist?. J Clin Neonatol 2022;11:117-23

How to cite this URL:
Harohalli A V, Anitha Raju N M, Narayanaswamy V. The neonatal lung ultrasound – What should i know as a neonatologist?. J Clin Neonatol [serial online] 2022 [cited 2022 May 18];11:117-23. Available from: https://www.jcnonweb.com/text.asp?2022/11/2/117/343421




  Introduction Top


Respiratory disease has taken the major share of admission into the neonatal intensive care unit. The identification of the etiology of respiratory disease is very crucial in critical management. The chest X-ray though is the gold standard in the diagnosis, the radiation impact on the rapidly replicating cells is very high in the neonates.[1]

The nonionizing radiation, ease to operate, performance in real-time, and reproducibility have made ultrasound an attractive utility in the diagnosis of neonatal lung disease.[2] The thin chest wall and low-volume lung have made this technique a useful modality in the diagnosis of lung disorder in neonates.[3]

The pleura, a horizontal hyperechogenic line on ultrasound, is the backbone for the diagnosis of different pathologies of the lung. The lung ultrasound makes use of artifacts taking the ratio of air and fluid. The knowledge of lung ultrasound is dealt with in a simple understandable way for the sake of neonatal residents to utilize this gadget in the care of sick neonates. The European Society of Pediatric and Neonatal Intensive Care has published the international evidence-based guidelines on point-of-care ultrasound in a standardized form.[4] This review article focuses on ultrasound of the normal lung, the techniques involved, and common lung pathologies.


  The Technique of Performing the Lung Ultrasound Top


The lung ultrasound is performed while nursing the baby in the supine position. The ideal curvilinear probe or linear probe of 10 MHz is used to perform the lung ultrasound for the better visualization of the images including pleura [Figure 1] and [Figure 2].[5] Each hemithorax is divided into six zones namely the anterior, between the parasternal line and the anterior axillary line, the lateral, between the anterior and the posterior axillary lines, and the posterior, between the posterior axillary line and paravertebral line.[6] Each division is horizontally split into upper and lower zones [Figure 3] and [Figure 4]. The probe is placed in each zone to study the lung. The hyperechogenic horizontally placed pleura is the only detectable structure on ultrasound in a normally aerated lung. The back and forth movement of the pleura with the breaths causes the lung to slide.[7] The reverberation of the pleura causes horizontal lines multiple with equidistant and parallel to each other and are called A-lines [Figure 5].[8] The vertical lines reverberating from the pleura erasing the A-lines and moving with the lung sliding constitute the B-lines-Comet tail. The multiple B-lines indicate alveolar-interstitial syndrome [Figure 6]. The Z-lines are the echogenic vertical lines reverberating from the pleural surface not erasing the A-lines and do not move with sliding [Figure 7].[9] These artifacts would be present until the lung fluid is resorbed.[10] Cutting the hyperechoic pleural line using the M mode, the structures above and below the pleural line demonstrate different configurations [Figure 8]. The structures above the pleura are static, hence resembling a sea, and the structure below the pleura is dynamic giving the lung a grainy (sand) appearance. This sign is called the seashore sign.[11],[12],[13],[14]
Figure 1: Curvilinear probe

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Figure 2: Linear probe

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Figure 3: Anterolateral division of chest into four compartments: upper anterior, lower anterior (between parasternal and anterior axillary line), upper lateral, and lower Lateral (between mid axillary line and posterior axillary line). The probe (P) is placed in each compartment. – Courtesy: H A Venkatesh

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Figure 4: The posterior upper and lower division (between the posterior axillary line and the paravertebral line-Courtesy: HA Venkatesh

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Figure 5: Healthy lung on ultrasound showing the pleura and the A-lines

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Figure 6: The lung ultrasound demonstrates the comet tails

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Figure 7: The Z-line is the echogenic vertical line from the pleura not erasing the A-line. This line mimics the B-line but does not move. Courtesy: H A Venkatesh

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Figure 8: The M-mode cuts the pleura demonstrating smooth horizontal lines above the pleura due to stationary tissue (Sea) and a fine granular sandy pattern below the pleura due to the disruption of the lines because of the lung motion. Here, the stationary chest wall and moving lung give the sea and sand pattern. Courtesy: H A Venkatesh

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  Lung Ultrasound Indications in the Neonate Top


The common indications for performing the bedside ultrasound of the lung in the neonatal period by the trained neonatologists include:

  • Diagnosis of lung diseases including respiratory distress syndrome (RDS), transient tachypnea of the newborn, meconium aspiration syndrome, and pleural effusion
  • Diagnosis of acute emergency – pneumothorax
  • Follow-up of the lung after the intervention
  • The diaphragm excursion
  • Bronchopulmonary dysplasia in preterm neonates.



  Neonatal Respiratory Distress Syndrome Top


Preterm neonates are born with RDS more often requiring respiratory care and endotracheal surfactant administration. The chest X-ray demonstrates a low-volume lung with symmetrical lung opacity [Figure 9]. The lung ultrasound of such neonates demonstrates coalescent B-lines with the absence of A-lines [Figure 10]. The irregular pleura with evidence of subpulmonic consolidation is seen.[15] The compact B-lines and the consolidations are concentrated predominantly in the posterior aspect of the lungs due to constant nursing supine, and hence, the posterior zones should be considered while performing the lung ultrasound.[16]
Figure 9: The chest X-ray demonstrates the low lung volume with symmetrical opaque lung featuring respiratory distress syndrome in a preterm neonate. Courtesy: H A Venkatesh

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Figure 10: The lung ultrasound demonstrates the confluent B-lines with absent A-lines suggesting respiratory distress syndrome. Courtesy: H A Venkatesh

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  Transient Tachypnea of the Newborn Top


The term and postterm neonates sometimes demonstrate respiratory distress due to failure in the reabsorption of fluid from the fetal lung leading to the wet lung disease – the transient tachypnea of the newborn. The chest X-ray shows the prominent horizontal fissure with streaky perihilar shadow indicating fluid in the lung [Figure 11]. The ultrasound in such babies shows double lung point, wherein the more compact B-lines in the lower lung field and less compact B-lines in the upper lung field [Figure 12]. Unlike in neonatal RDS, the pleural line is regular and there would be no subpleural consolidation. It is very crucial to differentiate the transient tachypnoea of newborns from the respiratory distress syndrome, especially in the first few hours of life.[17]
Figure 11: The chest X-ray demonstrating thickened horizontal – A feature of the transient tachypnea of the newborn. Courtesy: H A Venkatesh

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Figure 12: The ultrasound lung demonstrates 2 distinct zones. 1. Demonstrating A-lines indicating the aeration 2. Demonstrating Comet tails –B -lines. This is typically seen in the transient tachypnoea of the newborn (Double lung point). Courtesy: H A Venkatesh

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  Meconium Aspiration Syndrome Top


The meconium aspiration syndrome is most commonly seen in babies born postterm and small for gestational age. On clinical examination, hyperinflation of the chest is seen in addition to respiratory distress. Chest X-ray demonstrates hyperinflation with patchy opacities [Figure 13]. The ultrasound lung demonstrates coalescent B-lines asymmetric distribution of subpulmonic consolidation with a few spared areas [Figure 14].[18] The ultrasound features of the lung resemble the characteristic features of that of pneumonia.
Figure 13: The chest X-ray demonstrated hyperinflation with patchy opacities meconium aspiration syndrome. Courtesy: H A Venkatesh

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Figure 14: The lung ultrasound demonstrated irregular pleural line and subpleural consolidation with compact B-lines favoring meconium aspiration syndrome. Courtesy: H A Venkatesh

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  The Pleural Effusion Top


The sensitivity and the specificity of the lung ultrasound in the diagnosis of pleural effusion are close to 100%. It can pick up the fluid collection as small as 20 ml confirming the superiority over the chest X-ray [Figure 15]. The ultrasound image shows a dark anechoic shadow above the diaphragm and also helps in quantifying the volume of fluid in the space. The static sonographic sign, the quad sign, is well appreciated in pleural effusion [Figure 16]. The M-mode cutting the pleural line in effusion demonstrates the sinusoidal sign [Figure 17].[12],[14],[19]
Figure 15: The chest X-ray demonstrating the left-sided pleural effusion

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Figure 16: The ultrasound demonstrated the anechoic fluid in the pleural cavity. The quad sign represents the pleural effusion. It is a static sonographic sign representing the pleura, the rib, the fluid, and the lung. Courtesy: H A Venkatesh

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Figure 17: The M mode ultrasound cut the pleura and demonstrates dynamic sonographic sign called sinusoid sign –change in the size of pleral effusion with respiration forming a sinusoidal wave moving towards and away from pleural line

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  The Pneumothorax Top


The sudden deterioration of the neonate in the newborn intensive care unit, especially on a ventilator should make the clinician diagnose pneumothorax – a dreaded air-leak syndrome. The bedside ultrasound is more sensitive in picking up the pneumothorax than the X- ray [Figure 18]. The ultrasound features include the disappearance of pleural sliding due to the accumulation of air in the pleural cavity, the absence of B-lines, and a highly specific sign-the lung point wherein one can appreciate the transition between the sliding pleura and the still pleura.
Figure 18: The chest X-ray demonstrated pneumothorax (R) with the left lung collapsed

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The barcode sign also called the stratosphere sign is an important sign observed on performing the lung ultrasound [Figure 19]. This sign is demonstrated when the M-mode cuts the pleura, wherein the structure on either side of the pleura becomes static and looks uniformly the same resembling the barcodes.[11],[13],[20] The sensitivity, specificity, and positive predictive value of ultrasound for pneumothorax is 100%.[21]
Figure 19: The barcode sign – pneumothorax

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  The Ultrasound Diaphragm – An Integral Part While Performing the Lung Ultrasound Top


The ultrasound is an integral part of the evaluation of the functioning of the diaphragm. The 2 phases of respiration are well demonstrated on M- Mode ultrasound cutting the diaphragm [Figure 20] and [Figure 21]. The inspiratory and the expiratory excursion of the diaphragm helps to understand the symmetrical movement of the diaphragm and also in determining the correct endotracheal tip position.[22],[23]
Figure 20: Ultrasound M-mode cutting the diaphragm (R)

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Figure 21: Ultrasound M-mode cutting the diaphragm (L)

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  Bronchopulmonary Dysplasia Top


The most common morbidity seen in preterm neonates in the neonatal intensive care unit. The patchy and streaky shadowing is seen on chest X-ray [Figure 22]. The ultrasound lung demonstrates thickened pleura, subpulmonic consolidation, and nonhomogeneous distribution of confluent B lines [Figure 23].
Figure 22: The chest X-ray shows the features of chronic lung disease. Courtesy: HA Venkatesh

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Figure 23: The ultrasound lung demonstrates thickened pleura, subpulmonic consolidation, and nonhomogeneous distribution of confluent B lines. C-consolidation,P-pleura

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  Conclusion Top


The bedside ultrasound has made its way into the care of sick neonates because of its easy availability, accuracy, and early diagnosis of common lung disorders. The proper understanding of ultrasound physics and the techniques in getting better images is very essential while interpreting the images. The ultrasound pleura is the better term instead of the lung ultrasound as all the images and signs that we see at the lung are at the mercy of the presence of the pleura.



 
  References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17], [Figure 18], [Figure 19], [Figure 20], [Figure 21], [Figure 22], [Figure 23]



 

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  In this article
Abstract
Introduction
The Technique of...
Lung Ultrasound ...
Neonatal Respira...
Transient Tachyp...
Meconium Aspirat...
The Pleural Effusion
The Pneumothorax
The Ultrasound D...
Bronchopulmonary...
Conclusion
References
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