Journal of Pediatric Critical Care

P - ISSN : 2349-6592    |    E - ISSN : 2455-7099

Case Report
Year : 2016 | Volume : 3 | Issue : 4 | Page : 101-104

Lung ultrasound for diagnosis of pneumothorax in an infant

Tiago Henrique de Souza*, Marina Pavan Giatti**, Marcelo Barciela Brandão***

*Pediatric Intensivist
**Resident physician in Pediatric Critical Care Program
***Pediatric Intensivist –Department of Pediatrics - Faculty of Medical Sciences, Clinical Hospital of State University of Campinas – São Paulo – Brazil

Correspondence Address:

Tiago Henrique de Souza
Adress: José Luiz Camargo Moreira, 202 apt 2 block 2, Zip code: 13087511, Campinas-SP, Brazil,Phone: +55-19-981514355 email: souza.tiagohenrique@gmail.com
Received: 17-Aug-16/accepted: 23-Oct-16/Published online: 22-Nov-16

Source of Funding:None Conflict of Interest:None

DOI:10.21304/2016.0304.00149

Abstract
Point-of-care ultrasound provides rapid and accurate diagnostic imaging in an acute care setting. While thoracic ultrasonography has proved to be a useful technique for adults in the emergency department and intensive care units, few studies have evaluated this technique in children. In this case, we describe the presence of a pneumothorax, identified by point-of-care ultrasound in a 4-month-old infant in postoperative care after cardiac surgery. The infant presented with mild respiratory distress. A resident physician performed the exam, after recently completing ultrasound training.

Keywords: lung ultrasound; point-of-care ultrasound; pneumothorax; pediatric

Case Report
A 4-month-old infant (weighing 5 kg) diagnosed with endocarditis underwent cardiac surgery for removal of a right atrial vegetative lesion. Following surgery, the patient was transferred to the pediatric intensive care unit. At the time of admission, the patient was receiving supplemental oxygen by nasal catheter. Mediastinal drainage was measured. On physical examination, the patient appeared in good general physical condition. The patient was active, and well hydrated with good peripheral perfusion, strong peripheral pulse and healthy skin color. Heart rate was 162 beats per minute and respiratory rate 33 breaths per minute. Thoracic auscultation revealed a slight decrease in breath sounds on the right, when compared to the left side of the chest. No chest retractions were observed. Oxygen saturation was 98%. The point-of-care chest ultrasound, performed by a resident physician in the pediatric intensive care program. The patient was in the supine position and the examination was performed with a 12 Mhz linear transducer, positioned on the anterior right hemithorax, with a longitudinal and transverse orientation. The presence of "A - Lines", without evidence of lung sliding, was observed in the two-dimensional (2D) mode. With the M mode, the "stratosphere sign" was identified (Figure 1). Movement of the transducer to a more transverse position, toward the lateral chest, demonstrated the "lung point sign” (Figure 2). These sonographic findings are very specific for pneumothorax [1]. A chest radiograph confirmed this finding (Figure 3). After establishing pleural drainage, pulmonary expansion was confirmed by a second chest radiograph.

Discussion
Lung ultrasound performed in adults is more accurate than chest radiographs for the diagnosis of pneumothorax. In addition, when compared to computerized tomography, the gold standard for identifying a pneumothorax, the sensitivity and specificity of chest ultrasound is 95% and 100%, respectively [2-6]. However, studies in children are infrequent and there are no guidelines for routine use of chest ultrasound in pediatric patients.
This case report demonstrates the feasibility and ease of using point-of-care chest ultrasound to diagnosis pneumothorax in an infant weighing only 5 kg. In this study, pneumothorax was identified by a resident physician who had previously taken a 6-hour theoretical and practical ultrasound course. Ultrasound evaluation of pneumonia is highly accurate even when performed by inexperienced operators [7]. These studies suggest that physicians can become proficient at pediatric chest ultrasound with minimal training.
The lung and pleural can be evaluated using simple ultrasound devices that generate images in two dimensions. The most commonly used transducers are convex, linear and sector. Transducers with lower frequencies (convex and sector) are useful to assess deep structures. As the linear probe is a higher frequency probe, it is better suited to assess superficial structures (Figure 4). Due to small chest dimensions of young children, the linear probe not only provides visualization of the pleura, but also visualization of the lung parenchyma [7, 8].
A detailed assessment of the pleura and lung sliding is required in chest ultrasound. The absence of lung sliding can occur when air separates the pleural surfaces, as is the case with pneumothorax, or when the pleura are close together or adhered to each other. The major causes of contact between the visceral and parietal pleura, where sliding is not observed, are apnea, selective intubation, atelectasis and inflammatory adhesions. When there is clinical suspicion of a pneumothorax, chest ultrasound should be started in the anterior chest, progressing sideways with transducer [9].
The sonographic study of lung sliding utilizes both 2D and M mode ultrasound. With 2D, it is possible to observe the movement of hyperechoic points in the pleural line that move synchronously with respiration. This synchronous movement is characteristic of normal lung sliding. In patients with pneumothorax, the pleural line is static, despite respiratory movements. However, on occasion, the two-dimensional image of a normal chest may appear similar to the image of a pneumothorax, suggesting that the evaluation of lung sliding is essential for an accurate diagnosis. In patients with pneumothorax, the M-mode generates the "stratosphere sign", which is defined as the presence of multiple parallel straight lines below the pleural line, appearing similar to a bar code (Figure 1) [2, 3]. The identification of lung sliding on an ultrasound examination has a negative predictive value of 100% for pneumothorax [3].
B-lines are hyperechoic artifacts that appear as vertical lines and extend from the visceral pleura to the edge of the screen without fading. (Figure 5). These artifacts move synchronously with lung sliding and respiration. Pneumothorax can be ruled out by the presence of B-lines. [3, 9].
The most specific sonographic sign of pneumothorax is the "lung point sign", which can be difficult to identify [1]. The "lung point sign" can be found at the border of the pneumothorax and normal pleural interface. This sign is due to the sliding lung intermittently contacting the chest wall, and is evident when characteristics of the two regions are seen in the same sonographic image [1, 4]. Thus, the “lung point sign” is useful to determine both the size and position of the pneumothorax [5, 9]. In M mode, the lung point may be intermittently identified as images of "beach sign" or "sign the stratosphere", depending on the placement of the probe and the direction of the ultrasound beam during the respiratory cycle (Figure 3).
In 2013, Kosiak published the first study evaluating chest ultrasound for the diagnosis of iatrogenic pneumothorax in children [10]. Sixty-three patients (7.8 ± 5 years of age) underwent ultrasound examination after subclavian vein catheterization. Characteristic sonographic signs of pneumothorax were identified in four cases. The sensitivity, specificity and predictive values (positive and negative) were 100%. Although the sensitivity of chest radiographs was only 25%, because of the small sample size the authors were unable to conclude that ultrasound is a superior technique for identifying pneumothorax in children.
In 2014, Vitale et al described the use of chest ultrasonography in postoperative pediatric patients after cardiac surgery [11]. Four cases were reported, including a 30-day-old infant with the diagnosis of pneumothorax. In a case report the same year, Magliaro et al described thoracentesis guided by ultrasound in a clinically unstable preterm 680 g infant with a pneumothorax [12].
In 2015, Zhongheng Zhang described the only pediatric report of "double lung point" [13]. The image was taken in an 18-month-old child who presented to the pediatric emergency room in respiratory distress. Chest radiographs showed extensive right pneumothorax and computerized tomography showed a small accumulation of air between the visceral and parietal pleura in the left hemithorax. Chest ultrasound performed in the intensive care unit demonstrated two “lung point signs” in the left lung at the axillary line. The presence of two “lung point signs" is rare, previously described in only three adult patients. In all cases, the treatment was conservative, which suggests that this sign indicates a small pneumothorax.
Recently, the Lung Ultrasound in the Crashing Infant (LUCI) Protocol Study Group, evaluated the use of ultrasound in the diagnosis of pneumothorax in neonates (May 2016) [14]. The study involved six intensive care units from three European countries. Forty-two patients with sudden clinical deterioration were prospectively evaluated. Clinical deterioration was defined by oxygen desaturation and hemodynamic instability or the requirement to increase oxygen supply by 50% for at least 10 minutes to maintain adequate oxygenation. All examinations were performed by the neonatologist. In this study, the diagnosis of pneumothorax by chest ultrasound was extremely accurate, with sensitivity, specificity positive predictive, and negative predictive value of 100%. This study demonstrates the safety and efficacy of chest ultrasound for the diagnosis of pneumothorax in critically ill infants.
The use of chest ultrasound can also decrease exposure to radiation that accompanies routine chest radiographs. Guillaume Escourrou and Daniele De Luca reported a significant reduction in the use of radiographs in the neonatal intensive care unit after implementation of routine chest ultrasound [15]. In 2012, 81% of hospitalized infants had at least one chest radiograph. In 2014, after implementation of chest ultrasound, the routine use of chest radiographs was reduced to 69.7% (p <0.001). The reduction in the number of radiographic examinations for newborns resulted in a decrease in radiation exposure for these infants. The number of premature infants evaluated without exposure to radiation from routine radiographs increased to 30.3% in 2014.

Conclusion
This case report describes the successful use of chest ultrasound to diagnosis a pneumothorax in an infant. In this case, a resident physician successfully identified the classical characteristics of pneumothorax after a short training period. The adoption of new diagnostic methods in clinical pediatric practice requires responsibility and caution. Ultrasonography is a rapid, safe, and effective method of pulmonary evaluation in adult patients. Our report, and others, suggests that chest ultrasound has potential for improving care of critically ill pediatric patients. The routine use of the method could decrease exposure to radiation, as well as improve diagnosis, reduce costs, and provide an accurate assessment of the usual conditions in pediatrics.

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