Neonatal Radiolgy

Pneumomediastinum in the Neonate Kristi J. Cagle, RNC-NIC, BSN Column Editor Carol Trotter, PhD, RN, NNP-BC Continuing Nursing Education (CNE) Credit A total of 2 contact hours may be earned as CNE credit for reading the articles in this issue identified as CNE and for completing an online posttest and evaluation. To be successful the learner must obtain a grade of at least 80% on the test. Test expires three (3) years from publication date. Disclosure: The author/planning committee has no relevant financial interest or affiliations with any commercial interes ts related to the subjects discussed within this article. No commercial support or sponsorship was provided for this educational activity. ANN/ANCC does not endorse any commercial products discussed/displayed in conjunction with this educational activity. The Academy of Neonatal Nursing is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center ’s Commission on Accreditation. Provider, Academy of Neonatal Nursing, approved by the California B oard of R egis tered Nursing, Provider #CEP 6261; and Florida Board of Nursing, Provider #FBN 3218, content code 2505. The purpose of this article is to describe the pathophysiology, clinical symptoms, and radiographic features of a pneumomediastinum in the neonate.

Abstract A pneumomediastinum is an air leak in which the free air is concentrated in the mediastinum. Although most neonatal pneumomediastinums do not require intervention, complications such as subsequent air leaks can arise. Proper radiologic identification, as well as an understanding of the anatomy and pathophysiology associated with a pneumomediastinum, are necessary for an accurate understanding and diagnosis. This article will review the interpretation of radiologic findings in a neonate with a pneumomediastinum. Keywords: chest x-ray; neonate; pneumomediastinum

P

neumomediastinum, a diagnosis in

the class of air leak syndromes,1 is a condition in which air accumulates in the mediastinum. 2 This accumulation most often occurs due to barotrauma, resulting in rupture of bronchioles, alveolar ducts, or alveoli. 3 This air follows the path of least resistance as it moves toward the hilum continuing to the mediastinum.3 This phenomenon usually occurs shortly after birth or within the first few days of life.3 Neonates are particularly vulnerable to air leaks because of disease processes such as respiratory distress, hyaline membrane disease, and meconium aspiration.4

INCIDENCE OF PNEUMOMEDIASTINUM IN THE NEONATAL POPULATION

Accepted for publication February 2014.

Air leak syndromes are common in the neonatal population5 ; pneumomediastinum is the third most common type of air leak, preceded only by pulmonary interstitial emphysema and pneumothorax.4 The risk of pneumomediastinum increases as the birth weight decreases.1 Conditions in which the neonatal lungs are compromised, such as meconium aspiration, also tend to increase the incidence of pneumomediastinum.1

The incidence of pneumomediastinum in the NICU at the Children’s Hospital at Oklahoma University Medical Center was 0.6 percent (13 patients) for the twoyear period from June 1, 2011, thru June 30, 2013. Of those 13 patients, 5 developed a pneumothorax in addition to the pneumomediastinum. The purpose of this article is to identify the key aspects involved in identifying a pneumomediastinum on the neonatal chest x-ray. An understanding of the relevant anatomy and pathophysiology is important for accurate radiographic interpretation; therefore, these topics will be reviewed next. A case study will also be presented to highlight the clinical and radiographic features of pneumomediastinum.

ANATOMY

The mediastinum extends from the thoracic inlet to the diaphragm, consisting of the superior and inferior mediastinum, then further divides into the anterior mediastinum, middle mediastinum, and posterior mediastinum. The compartments of the mediastinum are depicted in Figure 1. The superior mediastinum begins at the thoracic inlet and ends at approximately the T4

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FIGURE 1  n  Compartments of the mediastinum. Sternal angle

Rib I

Superior mediastinum

Anterior mediastinum Middle mediastinum

Posterior mediastinum

Inferior mediastinum

Diaphragm

Note: The diagram of the mediastinum depicts the compartments and location of the mediastinum. The mediastinum is the area between the thoracic inlet and the diaphragm and the sternum and the spinal column. The mediastinum is first separated into a superior and inferior compartment. The inferior compartment holds the anterior, middle, and posterior mediastinum. From Drake R, Vogl AW, Mitchell A. Gray’s Anatomy for Students. 2nd ed. Philadelphia, PA: Elsevier; 2010. Copyright © Elsevier. Reprinted with permission.

vertebrae, extending across the chest cavity. The brachiocephalic veins, vena cava, aortic arch, and trachea are located within this area. The area from the back of the sternum to the pericardium and from approximately T4 extending all the way to the diaphragm makes up the anterior mediastinum, or the prevascular compartment. The pericardium, heart, pulmonary trunk, hilum, and tracheal bifurcation make up the middle mediastinum. The posterior mediastinal space exists between the pericardium and the spinal column, containing the descending aorta, azygos vein, and esophagus.6,7 The thymus gland and the area of the hilum are important to identify when evaluating the chest x-ray of a neonate and when considering a pneumomediastinum. The thymus gland, depicted in Figure 2, is a lobular organ located above the heart and may be easily manipulated by free air.8 The thymus occupies both the superior and anterior mediastinum and can have an inconsistent appearance with each patient.9 At birth, the thymus is large and visible on chest x-ray; however, in the presence of stress or disease, the size of the thymus may quickly regress. Therefore, the thymus may be minimal on the chest x-ray of a neonate undergoing prenatal stress.10 The pulmonary hilum is where the pulmonary vessels and bronchi intersect with each lung and is typically identified on x-ray as an area of increased density around the fourth and fifth intercostal spaces on each side of the cardiac silhouette9 (Figure 3). The increased density

FIGURE 2  n  Diagram of the anatomic location of the thymus.

Thyroid Thymus

Note: The thymus is a lobular organ that is located directly above the heart. Free air within the mediastinum may lift the lobes of the thymus away from the heart.

is because these hilar structures contain more water and less air than the lung and therefore appear more dense when superimposed over normally aerated lung tissue. The appearance of the hilar area may be altered in the presence of a pneumomediastinum.

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FIGURE 3  n  Diagram of the anatomic location of the hilum of the lungs.

FIGURE 4  n  Diagram of the movement of air in a pneumomediastinum.

lobar bronchus hilum of left lung medial surface

Note: The hilum of the lung consists of the area where the pulmonary vessels meet the bronchi of each lung. Copyright © Queen Mary University. Reprinted with permission.

ETIOLOGY/PATHOPHYSIOLOGY

Pneu momed iast i nu m i n t he neonate ca n occu r without an obvious cause, 11 although positive pressure or mechanical ventilation frequently precipitates a pneumomediastinum in neonates.1 Neonates with underdeveloped or diseased lungs usually have decreased lung compliance4 and are more vulnerable to alveolar rupture12 when treated with positive pressure ventilation (PPV).13 Once ruptured, air from the alveoli will follow the path of least resistance and move to areas of lower pressure,14 first moving to the interstitial spaces of the lung and then surrounding the vessels, bronchioles, and bronchi, penetrating the bronchovascular sheath continuing to move toward the hilum.4 This movement is depicted in Figure 4. From here, the air may breach into the mediastinum, creating the subsequent pneumomediastinum.4 It is thought that the pulsations and activity of the pulmonary vessels and the bronchi facilitate the continued migration of the air through the pulmonary vascular sheaths and into the mediastinum.14 Because of the supine positioning of newborns, this air typically accumulates on the anterior aspect of the mediastinum, although a posterior accumulation is a possibility.13 A pneumomediastinum that occurs without assisted PPV or trauma is called a spontaneous pneumomediastinum.11 In this type of pneumomediastinum, a drop in the interstitial pressure can result in an increase in alveolar pressure, causing air to be leaked from the alveoli into the interstitial spaces. 2,11 Chernick and Avery suggested that a spontaneous air leak is caused by a sequence of events: an aspiration of particles, such as meconium, followed by vigorous, high-pressured breaths directly after birth, leading to increased alveolar pressure, resulting in a rupture of the alveoli.15 During the infant’s first breaths, after birth,

Note: Schematic presentation of pathophysiology of pneumomediastinum. Alveolar rupture (A) lets alveolar air escape and dissect around the bronchioles and bronchi into the bronchovascular sheath (B) toward the hilum (C). Once in the mediastinum, the air extends around the large vessels (D) and esophagus (E) to the thoracic walls, especially behind the sternum (F). It can also penetrate into the spinal cord (G) or extend to beneath the parietal pleura (H), creating the extrapleural air sign. An ipsilateral or contralateral pneumothorax can occur either by rupture of the parietal sheet of the pleura (I) or after centrifugal air dissecting into the interstitium (J) by rupture of the visceral sheet of the pleura (K). From Chalumeau M, Le Clainche L, Sayeg N, et al. Spontaneous pneumomediastinum in children. Pediatr Pulmonol. 2001;31:6775. Copyright © 2001 Wiley-Liss, Inc. Reprinted with permission.

a high intra-alveolar pressure is initially needed to expand the alveoli and facilitate the adaptation to extrauterine breathing.16 If too much intra-alveolar pressure occurs or the alveoli are compromised or the air is trapped within the alveoli, then a rupture could occur, leading to the leakage of air from the alveoli to the surrounding tissues.15 An isolated pneumomediastinum usually has a selfresolving course with minimal complications.17 In an isolated pneumomediastinum, the amount of air accumulation in the mediastinum determines the degree of respiratory distress.18 If the amount of air is large enough, the increased pressure can impede blood flow both to and from the heart.14,18 Because the mediastinum serves as a critical juncture within the chest, serious complications can occur if the free air moves to other areas in the body.19 Figure 5 depicts the potential pathways of air migration following alveolar rupture. Although rare in the neonatal population, the superior mediastinal air can migrate into the subcutaneous area of the neck along the great vessels through the facial planes. 20 In 2011, Silfeler and colleagues described a case of a term infant, delivered via vaginal delivery without complications.17 The infant displayed mild respiratory distress

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FIGURE 5  n  Pathways of air migration after alveolar rupture.

Air passes along vessels to neck D Subcutaneous emphysema

C

Pneumomediastinum

Air enters plural cavity = Pneumothorax

Air passes to mediastinum

E

A Bronchiole

Bronchovascular Sheath

B

Alveolus

Air passes along bronchi to mediastinum

Arteriole

Venule

Retroperitoneal emphysema F

Note: Pathogenesis of pneumomediastinum and subcutaneous emphysema from airway obstruction. With alveolar rupture, air can dissect into the bronchoalveolar sheath (A) and enters the perivascular interstitium. The air then passes along the bronchi (B) to the mediastinum (C) or to the subcutaneous space. (D) Pleural rupture may cause pneumothorax (E). Air can extend to the peritoneum (F). From Gesundheit B, Preminger A, Harito B, Babyn P, Maayan C, Mei-Zahav M. Pneumomediastinum and subcutaneous emphysema in an 18-month-old child. J Pediatr. 2002;141(1):116-120. Copyright © Elsevier. Reprinted with permission.

after birth, and the chest x-ray revealed a pneumomediastinum complicated by cervical subcutaneous emphysema because of the migration of air into the subcutaneous tissue of the neck. This patient subsequently suffered from brachial palsy because of the pressure from the subcutaneous air. By Day 2, the pneumomediastinum had resolved, but the brachial palsy remained. Ultimately, this patient was discharged with plans to follow up with neurology as an outpatient.17 If the mediastinal air is located behind the heart in the posterior mediastinum, the mediastinal air can exert pressure on the heart, causing cardiac tamponade.13 Air in the posterior mediastinum can also migrate down the aorta or esophagus and into the abdominal cavity, resulting in a pneumoperitoneum. 3 In a case review by Rosenfeld, Cordell, and Jadeja, 5 of 14 neonatal patients with pneumomediastinum developed free air within the abdominal cavity.3 Pneumomediastinum and pneumothorax commonly occur together4 and can impact not only the severity of the

illness21 but the treatment course, as well.4 A pneumomediastinum can also be a precursor to a pneumothorax because, with enough pressure, the mediastinal air ruptures through either the parietal or visceral pleura and into the pleura space that outlines the lungs.22,23

SIGNS AND SYMPTOMS

A patient with an isolated, small pneumomediastinum may not exhibit any clinical signs or symptoms.1 Neonates may show signs of respiratory distress2 ; the severity of the respiratory distress will vary depending on the size of the pneumomediastinum and whether there are any other air leaks or coexisting lung diseases. 2,4 These signs can vary from mild restlessness5 and tachypnea4 to retractions and an increase in oxygen requirements.24 Any neonate with respiratory distress, no matter how mild, should be evaluated for an air leak.5 Decreased or distant heart tones may be auscultated in a patient with pneumomediastinum1,4 because of an

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accumulation of air in the anterior mediastinum in front of the heart which may muffle the heart tones.

FIGURE 7  n  Pneumomediastinum and left tension pneumothorax.

DIAGNOSIS

The diagnosis of pneumomediastinum is made by a chest x-ray.18 Generally, an anteroposterior (AP) chest x-ray is sufficient, although a lateral view may be indicated if the AP view is unclear, 21,25 such as when a medial pneumothorax mimics the appearance of a pneumomediastinum.26 The appearance of a pneumomediastinum on either view can vary depending on the amount of air and the areas of concentration.26 Air can collect within the mediastinum in a superior or inferior location as well as the anterior or posterior location (see Figure 1). Typically, an AP chest x-ray will show an elevated thymus that is caused by the accumulation of air in the mediastinum between the heart and the thymus.24 The thymus gland has two lobes, is located in the anterior and superior mediastinum, and, on AP x-ray view, appears to sit on top of the heart. When free air in the mediastinum lifts the lobes of the thymus away from the heart, the elevated lobes may appear as triangular densities on one or both sides. This sign is called the spinnaker sail sign 27 but has also been described as an angel wing25 or rocker-bottom8 appearance. The x-ray in Figure 6 depicts an infant with a pneumomediastinum and elevation of the thymus gland. Because free air on x-ray will appear black when compared with the more dense organs (heart and thymus) and diseased lungs,9 the mediastinal air will appear as lucent areas on the film, usually surrounding

Note: Anteroposterior chest x-ray of a 32-week-gestationalage, intubated infant receiving mechanical ventilation. The infant has a large left tension pneumothorax with the heart and mediastinal structures shifted to the right. The pneumomediastinum is demonstrated by the lucency adjacent to the left upper spine most likely in the superior mediastinum and the dark air lucency surrounding the sides and inferior edge of the heart. This inferior mediastinal air appears to lift the heart away from the diaphragm. An echocardiogram ruled out pneumopericardium.

FIGURE 6  n  Pneumomediastinum and left pneumothorax.

Note: Anteroposterior chest x-ray of a 38-week-gestational-age infant intubated and receiving mechanical ventilation. Note the elevated thymus on the right and left, confirming the pneumomediastinum. The density of the scapula on the right blends with the density of the thymus gland, obscuring the edge of the thymus gland (x-ray provided courtesy of Dr. Carol Trotter).

the cardiac and the thymic structures.27 In addition, if there is free air in the inferior mediastinum, the air may lift the heart away from the diaphragm producing the continuous diaphragm sign.20 Normally, the heart overlies the diaphragm so that the edge of the diaphragm, under the heart, is not clearly distinguishable from the heart. With a pneumomediastinum, the lucency from the free air may outline the edge of the diaphragm under the heart so that on AP chest x-ray it appears as a continuously visible diaphragm across the chest. 20 The visualization of free air in the mediastinum under the heart can be seen in Figure 7. Depending on the path that the free air takes, lucent appearance of air may be visualized along the left side of the heart and down the descending aorta, as well as traveling up the vessels of the neck.2 Three types of chest x-rays may be ordered to evaluate an infant for a pneumomediastinum: an AP, a cross-table lateral, and a lateral decubitus x-ray. An anterior pneumomediastinum without elevation of the thymus may be difficult to appreciate on the AP x-ray because of the density of the thymus that overlies the area. 24 If the diagnosis is questionable or to rule out a pneumothorax, a cross-table lateral chest x-ray or a lateral decubitus x-ray may aid in

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diagnosis. 21 In a cross-table lateral x-ray, any accumulation of mediastinal air either anterior or posterior to the heart will be more readily identifiable against the dense structures within the mediastinum.4 For a cross-table lateral chest x-ray, the patient is placed in the supine position, and the film is shot from the side. If the pneumomediastinum is large, the AP x-ray can mimic the appearance of pneumothoraces. In this case, a lateral decubitus x-ray should be obtained. 25 For the lateral decubitus film, the patient is positioned side-lying, and the film is shot from the side. On a lateral decubitus film, a pneumomediastinum that accumulates in the posterior area will demonstrate areas of lucency that protrude laterally to the cardiac borders. 3 In contrast, if a pneumothorax is present, with the patient in a side-lying position, the air from the pneumothorax will rise to the elevated side outlining the lateral lung border clearly outside of the mediastinal cavity. 20 Alternately, the mediastinal air will rise but will remain within the mediastinum. Both the cross-table lateral and lateral decubitus views allows for a more accurate interpretation of the condition. 24

TREATMENT

Most isolated pneumomediastinums will resolve on their own and require no invasive intervention 20 ; however, the patient should be monitored in a NICU.13 Supplemental oxygen at 100 percent FiO2 may be recommended for the term patient.4 Because the air trapped in the mediastinum is room air and composed of approximately 78 percent nitrogen, the administration of 100 percent FiO2 essentially causes nitrogen to be removed from the blood and tissues.15 This is also called a nitrogen washout procedure. When nitrogen is eliminated from the blood and surrounding tissues, the total tension of dissolved gases in the tissues drops precipitously. This pressure difference between the tissues and the trapped gas in the mediastinum favors movement of the gas from the area of high pressure to low pressure, facilitating the reabsorption of the trapped gas.15 If the patient is symptomatic, experiencing respiratory distress, serial chest x-rays may be warranted until resolution because pneumothoraces may develop.19 If additional air leaks develop, a needle aspiration or a chest tube may be required to evacuate the air.4,13 The following case study is presented to illustrate the course of events with a clinically stable neonate with a pneumomediastinum.

CASE STUDY

Baby “AB” was born at 40 1/7 weeks gestation to a G4P1 mother who is 31 years of age. The mother received routine prenatal care and had an uncomplicated pregnancy. She presented to the birth hospital for a scheduled induction at 40 0/7 weeks gestation, with a successful

progression of labor. Limited fetal data during labor were available; however, it was reported that generally there were normal fetal heart tones with good variability. Two late decelerations in the fetal heart rate were reported after the rupture of membranes, just prior to delivery with recovery back to the baseline heart rate. Spontaneous rupture of membranes (SROM) occurred, with clear fluid noted. The baby was delivered vaginally 22 minutes after the SROM, with terminal meconium noted. Baby AB presented cyanotic with no tone, respirations were shallow, and the heart rate was .100. Therefore, PPV was initiated, via the Neopuff, immediately after birth, transitioning to continuous positive airway pressure (CPAP) for approximately 30 minutes. Apgar scores of 3 (2—heart rate, 1— respirations, 0—tone, 0—reflex, 0—color), 6 (2—heart rate, 1—respirations, 1—tone, 1—reflex, 1—color), and 9 (2—heart rate, 2—respirations, 2—tone, 2—reflex, 1— color) were assigned at 1, 5, and 10 minutes, respectively. The baby was transitioned to flow by supplemental oxygen at approximately 30 minutes of age and then taken to the Level II NICU for continuation of care. The patient was then transitioned to room air at ~1 hour of life. Because of the terminal meconium and the need for PPV at delivery, AP and lateral chest x-ray were ordered at approximately 45 minutes of life. A pneumomediastinum and bilateral small pneumothoraces were noted on the x-rays (Figures 8 and 9). Arrangements were then made to transfer the patient to a Level IV NICU. Upon arrival of the transport team, Baby AB was on room air without grunting, retracting, or nasal f laring. The respiratory rate was 28 breaths per minute, and breath sounds were clear and equal bilaterally. Heart tones were auscultated with the point of maximum impulse noted to be at the lower left sternal border, which is normal and is supportive of no cardiac shift. No decrease in heart tones were appreciated by the transport team, which could indicate a large collection of air anterior to the heart. The patient was then transported to the receiving facility, on room air, via helicopter. Cardiorespiratory status remained stable during transport. On admission to the Level IV NICU, Baby AB’s room air, capillary blood gas was normal: pH 7.48, pCO2 33, pO2 58, base excess 1. Baby AB remained on room air, and an AP chest x-ray was ordered to evaluate the air leak (Figure 10). Because the follow-up x-ray demonstrated no enlargement of the pneumomediastinum or pneumothorax and Baby AB remained stable, he was offered and tolerated PO feedings. The intravenous (IV) fluids were discontinued on the day after admission. On DOL 2, the chest x-ray was repeated, demonstrating a decrease in the size of the pneumomediastinum and resolved pneumothoraces (Figure 11). The patient remained stable, on room air, and was discharged home on DOL 3, with an unremarkable NICU stay.

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FIGURE 8  n  Anteroposterior x-ray of term Baby AB at 45 minutes of age.

Note: The lung fields demonstrate a bilateral diffuse hazy appearance except where overlying areas of lucency exist. There is good lung expansion to the ninth rib on the right and ninth to tenth rib on the left. The thymus is visible as an area of increased density in both the right and left upper lobes. On the right, the area extends from approximately T3 to T5–T6, and on the left, it appears as a triangular area of density adjacent to the spine. The thymus is elevated above the heart, giving an angel wing appearance in the upper left lung lobe. The heart is visualized with sharp cardiac borders on the left. The cardiac borders on the right have a less sharp appearance because of the increased pulmonary vascularity of the hilar area. The heart is normal in size and placement without mediastinal shift or compression. There is an area of lucency visualized on both the right and left sides of the cardiac borders (see arrows), consistent with the appearance of a pneumomediastinum. The diaphragm is intact and is visualized at the level of T10 on the left and T9 on the right. The diaphragm has a flattened appearance on the left side. There is no continuous diaphragm sign because the density of the lower edge of the heart blends with the density of the diaphragm. A sharp costophrenic angle is visualized on the right. Small slivers of lucency are visualized in the bases of each lung, supporting the diagnosis of small bilateral pneumothoraces. Impression: pneumomediastinum and small bilateral subpulmonic pneumothoraces.

FIGURE 9  n  Cross-table lateral x-ray of Baby AB at approximately 45 minutes of age.

Note: The cross-table lateral view shows a large, retrosternal lucency anterior to the heart (see arrows). This x-ray confirms the diagnosis of pneumomediastinum.

FIGURE 10  n  Anteroposterior x-ray of Baby AB upon admission to the Level IV NICU.

Note: The pneumomediastinum remains present and visible with continued elevation of the thymus, away from the heart. The air in the mediastinum is best visualized on the right underneath the thymus (see arrows). Very small lucencies remain visible in the right and left subpulmonic areas above the diaphragm.

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FIGURE 11  n  Anteroposterior x-ray of Baby AB on DOL 2.

Residual pneumomediastinum visualized with continued thymic elevation noted on the left (see arrow). Areas of lucency around the right and left sides of the heart are decreasing in size compared with previous films but are still present, particularly under the thymus on the left. The small bilateral pneumothoraces are resolved.

CONCLUSION

Most pneumomediastinums in the neonatal population will resolve without medical intervention. However, close monitoring is necessary to identify possible complications. Bedside nurses are often the first caregivers to identify a change in the neonate’s status. With the understanding of the pathophysiology and risk factors for pneumomediastinum along with knowledge of the identifying characteristics on x-ray, nurses can play a key role in alerting the health care team to the possibility of a pneumomediastinum.

REFERENCES

  1. Jeng MJ, Lee YS, Tsao PC, Soong WJ. Neonatal air leak syndrome and the role of high-frequency ventilation and its prevention. J Chin Med Assoc. 2012;75:551-559.   2. Hauri-Hohl A, Baenziger O, Frey B. Pneumomediastinum in the neonatal and paediatric intensive care unit. Eur J Pediatr. 2008;167:415-418.   3. Rosenfeld DL, Cordell CE, Jadeja N. Retrocardiac pneumomediastinum: radiographic finding and clinical implications. Pediatrics. 1990;85:92-97.  4. Hafis Ibrahim CP, Ganesan K, Mann G, Shaw NJ. Causes and management of pulmonary air leak in newborns. Pediatr Child Health. 2009;19:165-170.  5. Malek A, Afzali N, Meshkat M, Yazdi NH. Pneumothorax after mechanical ventilation in newborns. Iran J Pediatr. 2011;21:45-50.  6. Ronson RS, Duarte I, Miller JI. Embryology and surgical anatomy of the mediastinum with clinical implications. Surg Clin North Am. 2000;80:157-169.   7. Lee YT. The mediastinum. Gastrointest Endosc. 2009;69:S81-S83.   8. Kogutt MS. Rocker-bottom thymus a new sign of pneumomediastinum in the neonate. JAMA. 1981;246:770-771.   9. Trotter C, Carey BE. Radiology basics: overview and concepts. Neonatal Netw. 2000;19:35-47. 10. Nasseri F, Eftekhari F. Clinical and radiologic review of the normal and abnormal thymus: pearls and pitfalls. Radiographics. 2010;30:413-428.

Kelly S, Hughes S, Nixon S, Paterson-Brown S. Spontaneous 11. pneumomediastinum (Hamman’s syndrome). Surgeon. 2010;8:63-66. 12. Hall RT, Rhodes PG. Pneumothorax and pneumomediastinum in infants with idiopathic respiratory distress syndrome receiving continuous positive airway pressure. Pediatrics. 1975;55:493-496. 13. Kyle A, Veldtman G, Stanton M, Weeden D, Baral V. Barotraumaassociated posterior tension pneumomediastinum, a rare cause of cardiac tamponade in a ventilated neonate: a case report and review of the literature. Acta Paediatr. 2011;101:e142-e144. 14. Macklin CC. Transport of air along sheaths of pulmonic blood vessels from alveoli to mediastinum. Arch Intern Med. 1939;64:913-929. 15. Chernick V, Avery ME. Spontaneous alveolar rupture at birth. Pediatrics. 1963;32:816-824. 16. Sinha SK, Donn SM. Fetal-to-neonatal maladaptation. Semin Fetal Neonatal Med. 2006;11:166-173. 17. Silfeler I, Kurnaz H, Acar Y, Arica V, Tutanc M, Pekun F. Spontaneous pneumomediastinum associated with subcutaneous emphysema causing brachial plexus palsy in a term newborn. Pak J Med Sci. 2011;27:190192. 18. Lee CY, Wu CC, Lin CY. Etiologies of spontaneous pneumomediastinum in children of different ages. Pediatr Neonatol. 2009;50:190-195. 19. Kirkpatrick BV, Felman AH, Eitzman DV. Complications of ventilator therapy in respiratory distress syndrome. Am J Dis Child. 1974;128:496502. 20. Gesundheit B, Preminger A, Harito B, Babyn P, Maayan C, Mei-Zabav M. Pneumomediastinum and subcutaneous emphysema in an 18-monthold child. J Pediatr. 2002;141:116-120. 21. Chalumeau M, Le Clainche L, Sayeg N, et al. Spontaneous pneumomediastinum in children. Pediatr Pulmonol. 2001;31:67-75. 22. Kirby C, Trotter C. Pneumothorax in the neonate: assessment and diagnosis. Neonatal Netw. 2005;24:49-55. 23. Thibeault DW, Lachman RS, Laul VR, Kwong MS. Pulmonary interstitial emphysema, pneumomediastinum, and pneumothorax occurrence in the newborn infant. AM J Dis Child. 1973;126:611-614. 24. Lee CT, Tsao PN, Peng SS, et al. Spontaneous multiseptated cystic pneumomediastinum in a term newborn. Pediatr Neonatol. 2008;49: 197-200. 25. Carey BE. Neonatal air leaks: pneumothorax, pneumomediastinum, pulmonary interstitial emphysema, pneumopericardium. Neonatal Netw. 1999;18:81-84. 26. Zylak CM, Standen JR, Barnes GR, Zylak CF. Pneumomediastinum revisited. Radiographics. 2000;20:1043-1057. 27. Miller LK, Calenoff L, Boehm JJ, Riedy MJ. Respiratory distress in the newborn. JAMA. 1980;243:1176-1179.

About the Author

Kristi J. Cagle, RNC-NIC, BSN, is a graduate student in the Neonatal Nurse Practitioner Program at the University of MissouriKansas City. She received her Associates Degree in Nursing from Oklahoma City Community College and her Bachelors Degree in Nursing from Oklahoma City University. Kristi has 6 years of NICU experience and is currently employed as a Neonatal Flight Nurse at the University of Oklahoma Health Sciences Center. For further information, please contact: Kristi J. Cagle, RNC-NIC, BSN University of Oklahoma Health Sciences Center Attn: Neoflight / Kristi Cagle 1200 Everett Drive, 7th floor, North Pavilion Oklahoma City, OK 73104 E-mail: [email protected]

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Pneumomediastinum in the neonate.

A pneumomediastinum is an air leak in which the free air is concentrated in the mediastinum. Although most neonatal pneumomediastinums do not require ...
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