eMedicine Specialties > Radiology > Pediatrics

Pulmonary Interstitial Emphysema

Beverly P Wood, MD, PhD, Professor Emerita, Departments of Radiology and Pediatrics, Division of Medical Education, Keck School of Medicine, University of Southern California; Professor of Clinical Radiology, Loma Linda University School of Medicine

Updated: Jun 18, 2008

Introduction

Background

Pulmonary interstitial emphysema (PIE) is an iatrogenic pulmonary condition of the premature infant with immature lungs. PIE occurs almost exclusively in association with mechanical ventilation. The ventilatory pressure used to keep the alveolar ducts open also may cause the alveolar duct to rupture (usually at the junction of the bronchiole and alveolar duct); this in turn leads to the escape of air into the pulmonary interstitium, lymphatics, and venous circulation.^1,2

Close-up examination shows the typical linear pattern of pulmonary interstitial emphysema.

Pathophysiology

The cut section of the lung shows gas dissecting through the interstitium.

Histologic section showing gas within the interstitium, mainly in lymphatic vessels. The pulmonary tissue is atelectatic.

The surface of the lung in pulmonary interstitial emphysema shows subpleural lymphatics distended with air.

Excessive intra-airway pressure may cause gas to leak from the alveolar ducts (primordial acini) into the lung interstitium. Once in the interstitium, the gas is picked up in the rich lymphatic network of the neonate and is carried toward the pleural lymphatics and central bronchopleural lymphatics. PIE usually occurs early during ventilation; most infants with PIE present in the first 72 hours.

PIE occurs less frequently now because immature babies are treated with exogenous surfactant; such treatment increases lung compliance (thus reducing the need for ventilatory pressure) and keeps the alveolar ducts open during both inspiration and expiration.³ It also assists in the recruitment of alveolar ducts to prevent areas of overinflation and underinflation. Currently, PIE is seen more often in infants with bronchopulmonary dysplasia (BPD) who receive long-term ventilator therapy with uneven aeration; in such patients, PIE results from air trapping and airspace rupture.

Frequency

United States

Several decades ago, PIE was a common occurrence in infants with severe respiratory distress on ventilators. Currently, it is an uncommon occurrence because of treatment with surfactant and gentle ventilation, as well as the availability of high-frequency oscillatory ventilation for infants who are difficult to maintain with conventional ventilation.

Mortality/Morbidity

In the past, the mortality associated with PIE was high because the lungs became stiff and gas freely dissected into the interstitium, where oxygen absorption was poor. With rapid measures of prevention and alternative ventilatory improvement, approximately 25% of the infants survived, but all developed severe BPD.

• Complications of PIE include marked loss of pulmonary compliance, eventual epithelialization of the interstitial air pockets, embolus of air into the pulmonary venous circulation, and rupture of subpleural lymphatic blebs into the pleural space with pneumothorax. Infants with PIE inevitably develop BPD. Rupture of bronchiolar connections and release of air into the interstitium promotes edema and oxidant injury in the interstitium.

Sex

PIE is seen with equal frequency in both sexes.

Age

PIE is seen in premature infants usually younger than 32 weeks' gestation and who weigh less than 1200 g. PIE occurs in the first 72 hours of life, although it may be observed as a complication of prolonged positive pressure ventilation in the older premature infant.

Anatomy

PIE may occur diffusely throughout the lung, or it may be unilateral or lobar in occurrence. When PIE is local, the surrounding lung is often compressed as the region with PIE enlarges. The lesion of PIE is mechanical distention (and overdistention) of the alveolar ducts (precursors to alveoli and acini), which causes the ducts to rupture; alternatively, rupture occurs at the relatively weak junction of the alveolar duct and its bronchiole. After rupture, the air leak persists with the pressure of ventilation and motion of respiration. Gas is free to dissect into the interstitium, where it may remain or be taken up by the pulmonary lymphatic system. Cysts and overdistention of the lung reflect the effect of gas within the interstitium.

Presentation

PIE develops in infants who have established pulmonary disease of prematurity with respiratory distress syndrome who are being treated with supplemental oxygen, endotracheal intubation, and positive pressure mechanical ventilation. Most premature infants at risk for respiratory distress syndrome are treated with endotracheal surfactant, which improves pulmonary expansion, lung compliance, and oxygen exchange. PIE often occurs rapidly, arising in one region of the lung and quickly involving multiple lobes with fixed hyperexpansion, causing the clinical condition to worsen. Oxygen saturation of the blood falls, and ventilatory requirements increase.⁴

Emergent management takes several forms: initiation of high-frequency oscillatory ventilation with the rapid exchange of low volumes of gas at low pressure and, if PIE is localized, selective intubation of the airway bypassing the bronchus to the involved lobe.^5,6

Studies have demonstrated the presence of free elastase and alpha ₁ -proteinase inhibitor, as well as elastase-alpha ₁ -proteinase inhibitor, in tracheal aspirate fluid of neonates with severe respiratory distress syndrome. Infants who develop PIE appear to have free elastase activity in tracheal aspirate fluid. Elastolytic damage and barotrauma may contribute to acute pulmonary injury and PIE in the early stages of respiratory distress syndrome.⁷

Preferred Examination

Clinical examination involves the evaluation of pH and arterial oxygen saturation in proportion to the fraction of inspired oxygen.

PIE may be identified with a frontal chest radiograph. Disease progression is assessed with sequential studies.⁸

Limitations of Techniques

In an ill infant, it may be difficult to differentiate PIE from lucent overdistention of the bronchioles, though overdistended distal airways tend to be round and of uniform diameter, whereas PIE tends to be ovoid in the direction of the bronchovascular bundles; in addition, the lesions of PIE tend to be of different sizes. It is also difficult to differentiate PIE from early BPD with uneven patterns of aeration.

Differential Diagnoses

Bronchopulmonary Dysplasia
Hyaline Membrane Disease

Radiography

Findings

Anteroposterior examination of the chest at age 1 hour in this 27-week premature infant shows severe diffuse respiratory distress syndrome.

At 7 hours, the lungs are overexpanded with multiple linear areas of lucency, indicating pulmonary interstitial emphysema.

Pulmonary interstitial emphysema developing in an infant with respiratory distress syndrome at age 1 day.

By age 2 days, the infant has not improved, and pulmonary interstitial emphysema is more extensive.

Shortly before death, despite efforts to decrease ventilatory pressures, the lungs remain hyper-aerated with diffuse pulmonary interstitial emphysema.

Air in the lymphatics may rupture, causing pneumothorax, and can dissect into the peritoneum through potential openings in the diaphragm. This infant has pulmonary interstitial emphysema, pneumothoraces, and pneumoperitoneum.

Degree of Confidence

Linear gas collections in the periphery of the lung, in association with an increased demand for respiratory support, are diagnostic of PIE. Increasing lung volumes also strongly support a diagnosis of PIE.

False Positives/Negatives

Early BPD may present as focal areas of hyperaeration secondary to partial bronchial obstruction. The pattern closely resembles PIE, although the lucency is less linear in BPD. At histopathology, many lungs of infants with BPD demonstrate PIE that was not seen radiographically.

Intervention

When PIE is localized, it is extremely helpful to selectively ventilate unaffected lung so as to bypass the affected lobe or lobes. Radiologic imaging can assist by determining the location of the endotracheal tube. Radiologic imaging is also useful in monitoring for the potential complication of pneumothorax.

Placing the infant in the decubitus position with the affected side down can be of help when the diagnosis of unilateral PIE is made.^9,10,11,12

Medicolegal Pitfalls

• Because of the high morbidity and mortality associated with PIE, physicians have used various methods to ventilate infants with noncompliant lungs, including inhaled nitrous oxide, high-frequency ventilation, and extracorporeal membrane oxygenation.

See also the Medscape topic Medical Malpractice and Legal Issues.

Multimedia

Media file 1: Anteroposterior examination of the chest at age 1 hour in this 27-week premature infant shows severe diffuse respiratory distress syndrome.

Media file 2: At 7 hours, the lungs are overexpanded with multiple linear areas of lucency, indicating pulmonary interstitial emphysema.

Media file 3: Pulmonary interstitial emphysema developing in an infant with respiratory distress syndrome at age 1 day.

Media file 4: By age 2 days, the infant has not improved, and pulmonary interstitial emphysema is more extensive.

Media file 5: Close-up examination shows the typical linear pattern of pulmonary interstitial emphysema.

Media file 6: Shortly before death, despite efforts to decrease ventilatory pressures, the lungs remain hyper-aerated with diffuse pulmonary interstitial emphysema.

Media file 7: The cut section of the lung shows gas dissecting through the interstitium.

Media file 8: Histologic section showing gas within the interstitium, mainly in lymphatic vessels. The pulmonary tissue is atelectatic.

Media file 9: The surface of the lung in pulmonary interstitial emphysema shows subpleural lymphatics distended with air.

Media file 10: Air in the lymphatics may rupture, causing pneumothorax, and can dissect into the peritoneum through potential openings in the diaphragm. This infant has pulmonary interstitial emphysema, pneumothoraces, and pneumoperitoneum.

Media file 11: Gas dissects into the interstitium from ruptured airspaces and is rapidly taken up by lymphatics in the interstitium.

References

1. Cochran DP, Pilling DW, Shaw NJ. The relationship of pulmonary interstitial emphysema to subsequent type of chronic lung disease. Br J Radiol. Dec 1994;67(804):1155-7. [Medline].

2. Roll C, Hanssler L, Voit T. Case 30-1997: pulmonary interstitial emphysema in infancy [letter; comment]. N Engl J Med. Mar 5 1998;338(10):689-90. [Medline].

3. Soll, RF, Morley, CJ. Cochrane Database Syst Rev 2001;2:CD000510Prophylactic versus selective use of surfactant in preventing morbidity and mortality in preterm infants. Cochrane Review. 2001;2:CD000510.

4. Stevens TP, Harrington EW, Blennow M, Soll RF. Early surfactant administration with brief ventilation vs. selective surfactant and continued mechanical ventilation for preterm infants with or at risk for respiratory distress syndrome. Cochrane Database Syst Rev. Oct 17 2007;CD003063. [Medline].

5. Nelle M, Zilow EP, Linderkamp O. Effects of high-frequency oscillatory ventilation on circulation in neonates with pulmonary interstitial emphysema or RDS [see comments]. Intensive Care Med. Jun 1997;23(6):671-6. [Medline].

6. Plavka R, Kopecky P, Sebron V. A prospective randomized comparison of conventional mechanical ventilation and very early high frequency oscillatory ventilation in extremely premature newborns with respiratory distress syndrome. Intensive Care Med. Jan 1999;25(1):68-75. [Medline].

7. Speer CP, Ruess D, Harms K. Neutrophil elastase and acute pulmonary damage in neonates with severe respiratory distress syndrome. Pediatrics. Apr 1993;91(4):794-9. [Medline].

8. Jabra AA, Fishman EK, Shehata BM. Localized persistent pulmonary interstitial emphysema: CT findings with radiographic-pathologic correlation. AJR Am J Roentgenol. Nov 1997;169(5):1381-4. [Medline].

9. Ahluwalia JS, Rennie JM, Wells FC. Successful outcome of severe unilateral pulmonary interstitial emphysema after bi-lobectomy in a very low birth weight infant. Journal of the Royal Society of Medicine. March, 1996;89:167-168.

10. [Best Evidence] Greenough A, Dimitriou G, Prendergast M, Milner AD. Synchronized mechanical ventilation for respiratory support in newborn infants. Cochrane Database Syst Rev. Jan 23 2008;CD000456. [Medline].

11. Chalak LF, Kaiser JR, Arrington RW. Resolution of pulmonary interstitial emphysema following selective left main stem intubation in a premature newborn: an old procedure revisited. Paediatr Anaesth. Feb 2007;17(2):183-6. [Medline].

12. Thayyil S, Nagakumar P, Gowers H, Sinha A. Optimal endotracheal tube tip position in extremely premature infants. Am J Perinatol. Jan 2008;25(1):13-6. [Medline].

Keywords

acquired cystic lung disease of the premature infant, barotrauma of the premature lung interstitium, PIE

Contributor Information and Disclosures

Author

Beverly P Wood, MD, PhD, Professor Emerita, Departments of Radiology and Pediatrics, Division of Medical Education, Keck School of Medicine, University of Southern California; Professor of Clinical Radiology, Loma Linda University School of Medicine
Beverly P Wood, MD, PhD is a member of the following medical societies: American Academy of Pediatrics, American Association for Women Radiologists, American College of Radiology, American Institute of Ultrasound in Medicine, American Medical Association, American Roentgen Ray Society, Association of University Radiologists, Radiological Society of North America, and Society for Pediatric Radiology
Disclosure: Nothing to disclose.

Medical Editor

Robert J Starshak, MD, Medical Director, Assistant Clinical Professor, Department of Radiology, Medical College of Wisconsin, Falls Medical Group
Disclosure: Nothing to disclose.

Pharmacy Editor

Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.

CME Editor

Robert M Krasny, MD, Consulting Staff, Department of Radiology, Resolution Imaging Medical Corporation
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.

Chief Editor

John Karani, MBBS, FRCR, Clinical Director of Radiology and Consultant Radiologist, Department of Radiology, King's College Hospital, London
John Karani, MBBS, FRCR is a member of the following medical societies: British Institute of Radiology, British Society of Interventional Radiology, Cardiovascular and Interventional Radiological Society of Europe, European Society of Gastrointestinal and Abdominal Radiology, European Society of Radiology, Radiological Society of North America, and Royal College of Radiologists
Disclosure: Nothing to disclose.

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