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Radiological Case of the Month
Hal E. Crosswell, MD;
Dan L. Stewart, MD
From the Department of Pediatrics (Dr Crosswell) and Division of Neonatology
(Dr Stewart), University of Louisville School of Medicine and Kosair Children's
Hospital, Louisville, Ky.
Arch Pediatr Adolesc Med. 2001;155:615-616.
A MALE INFANT of 35 weeks' gestational age had mild respiratory distress
shortly after birth. He weighed 2640 g after a pregnancy complicated by breech
presentation and pregnancy-induced hypertension, resulting in a cesarean delivery
with clear amniotic fluid and no risk factors for infection. Apgar scores
were 7 and 8 at 1 and 5 minutes, respectively.
During transport to the newborn nursery, the infant became dusky, developed
sternal retractions, and showed 81% oxygen saturation by pulse oximetry. He
was afebrile, and findings from physical examination revealed tachypnea, subcostal
retractions, and decreased breath sounds present on the left. Therapy was
begun with delivery of supplemental oxygen by hood at a fraction of inspired
oxygen of 35%. Levels for serial C-reactive proteins and complete blood cell
count were normal as were findings from blood culture. Antibiotic therapy
was started on admission to the intermediate care nursery. The arterial blood
gas level 2 hours after birth showed a pH of 7.22; PaO2, 60 mm
Hg; and PaCO2, 58 mm Hg. A chest radiograph was obtained and repeated
6 hours later (Figure 1 and Figure 2). Within 6 hours, after management
by positioning in the left lateral decubitus position and delivery of oxygen
by nasal cannula, the respiratory distress, hypercarbia, and acidosis had
improved. The infant was discharged following 10 days of antibiotic therapy
for presumed pneumonia.
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Figure 1.
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Figure 2.
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Denouement and Discussion: Pulmonary Interstitial Emphysema in a Nonventilated Preterm Infant
Figure 1. Chest radiograph
(anterior-posterior view) showing left lower lobe consolidation with multicystic
and linear lucencies of pulmonary interstitial emphysema.
Figure 2. Repeated chest radiograph
(anterior-posterior view) 6 hours later showing almost complete resolution
of pulmonary interstitial emphysema.
Respiratory distress is a frequent problem encountered in newborn infants.
In the preterm infant, respiratory distress syndrome occurs resulting from
decreased production of surfactant. Signs of tachypnea, sternal retractions,
and hypoxia in the near- or full-term infant can be caused by transient tachypnea
of the newborn, associated with delayed resorption of fetal lung fluid. In
both the preterm and full-term child, respiratory distress may indicate pneumonia,
sepsis, congenital heart disease, anemia, central hypoventilation associated
with asphyxia, or intrinsic pulmonary mass.
Pulmonary interstitial emphysema (PIE) is encountered in very low-birth-weight
infants in the first 48 to 96 hours of life. The infants receive mechanical
ventilatory assistance because of poorly compliant or immature lungs. Resultant
volutrauma1 leads to rupture of overdistended
alveoli and resultant dissection of air into the interstitium—the bronchovascular
bundles, interlobular septa, and lymphatic channels.2
The diagnosis is based on radiography. Dissection of extra-alveolar air into
the pleural leads to air-leak syndromes such as pneumothorax, pneumomediastinum,
and pneumopericardium.
Pulmonary intersitial emphysema is considered an air "trap/leak" syndrome
because alveolar air enters the interstitium and is also trapped by a check-valve
phenomenon either at the site of dissection or from partial airway obstruction.3, 4 Partial bronchiolar obstruction
results from aspiration of foreign material, endobronchial plug, or fluid,
resulting in uneven expansion of the lung and abnormally high intra-alveolar
pressures,5, 6 which may
lead to PIE. Pulmonary interstitial emphysema occurred more frequently prior
to the use of positive pressure ventilation (PPV). Localized PIE in an infant
who has not received PPV may be mistaken for a different cause of respiratory
distress such as lung cysts, congenital lobar emphysema, or cystic adenomatoid
malformation.
Pulmonary interstitial emphysema can occur in up to one third of infants
receiving conventional mechanical ventilation who weigh less than 1500 g with
the incidence inversely proportional to decreasing weight. A review of 210
neonates mechanically ventilated for respiratory distress syndrome identified
41 with PIE. The most notable causative factor was high-peak inspiratory pressure.3, 7 Based on clinical, radiological,
and pathological criteria, PIE is categorized as acute pulmonary interstitial
emphysema, localized persistent interstitial emphysema, and diffuse persistent
pulmonary interstitial emphysema. The persistent type is associated with the
presence of giant cells, and when diffuse, it is associated with poor outcome.2
Treatment of a nonventilated infant with acute localized pulmonary emphysema
should be conservative, including positioning with the affected side down,
inhaled oxygen therapy by nasal cannula or oxygen hood and frequent monitoring
of blood gases and chest radiographs. In seriously ill infants, extracorporeal
membrane oxygenation, steroids, surgical resection, and high-frequency ventilation
have been used.8
Pulmonary interstitial emphysema is a well-recognized complication of
PPV for low-birth-weight infants but is an unusual occurrence in mature infants.
The cause of the interstitial leak in this patient is thought to be secondary
to partial obstruction of the lower lobe airways.
AUTHOR INFORMATION
Accepted for publication May 6, 1999.
Reprints: Dan L. Stewart MD, Division of Neonatal Medicine, Department
of Pediatrics, University of Louisville School of Medicine, 571 S Floyd, Suite
342, Louisville, KY 40202-3830 (e-mail: dlstew01{at}gwise.louisville.edu).
REFERENCES
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1. Clark RH. High-frequency ventilation. J Pediatr. 1994;124:661-670.
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2. Jabra AA, Fishman EK, Shehata BM, Perlman EJ. Localized persistent pulmonary interstitial emphysema: CT findings
with radiographic-pathologic correlation. Am J Roentgenol. 1997;169:1381-1384.
FREE FULL TEXT
3. Case records of the Massachusetts General Hospital: weekly clinicopathological
exercises: case 30-1997: a preterm newborn female triplet with diffuse cystic
changes in the left lung. N Engl J Med. 1997;337:916-924.
FREE FULL TEXT
4. Prosser R. Interstitial emphysema in the newborn. Arch Dis Child. 1964;39:236-239.
5. Stocker JT, Madewell JE. Persistent interstitial emphysema: another complication of the respiratory
distress syndrome. Pediatrics. 1977;59:847-857.
FREE FULL TEXT
6. Murray GF, Talkbert JL, Hailer JA Jr. Obstructive lobar emphysema of the newborn infant: documentation of
the "mucus plug syndrome" with successful treatment by bronchotomy. J Thorac Cardiovasc Surg. 1967;53:886-890.
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7. Greenough A, Dixon AK, Robertson NRC. Pulmonary interstitial emphysema. Arch Dis Child. 1984;59:1046-1051.
ABSTRACT
8. Mohsini K, Reid D, Tanswell K. Resolution of acquired lobar emphysema with dexamethasone therapy. J Pediatr. 1987;111:901-904.
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SECTION EDITOR: BEVERLY P. WOOD, MD
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