Anemia of Prematurity - Portal Neonatal

Pulmonary Interstitial Emphysema
Last Updated: May 29, 2002
Synonyms and related keywords: PIE, respiratory distress syndrome, RDS, meconium aspiration
syndrome, MAS, amniotic fluid aspiration
AUTHOR INFORMATION Section 1 of 10
Author: Abhay J Bhatt, MD, Assistant Professor, Department of Pediatrics, Division of Newborn
Medicine, University of Mississippi Medical Center
Coauthor(s): Rita M Ryan, MD, Associate Professor of Pediatrics, State University of New York
at Buffalo; Chief, Division of Neonatology, Director of Neonatal-Perinatal Medicine Fellowship
Program, Department of Pediatrics, Women's and Children's Hospital of Buffalo
Abhay J Bhatt, MD, is a member of the following medical societies: American Academy of
Pediatrics
Editor(s): Steven M Donn, MD, Professor of Pediatrics, Director, Neonatal-Perinatal Medicine,
Department of Pediatrics, University of Michigan Health System; Robert Konop, PharmD,
Director, Clinical Account Management, Ancillary Care Management; Brian S Carter, MD,
Associate Director, Associate Professor, Department of Pediatrics, Division of Neonatology,
Vanderbilt University Medical Center and Gateway Medical Center; Carol L Wagner, MD,
Associate Professor, Department of Pediatrics, Division of Neonatology, Medical University of
South Carolina; and Neil N Finer, MD, Director, Division of Neonatology, Professor, Department
of Pediatrics, University of California at San Diego
INTRODUCTION Section 2 of 10
Background: Pulmonary interstitial emphysema (PIE) is a collection of gases outside of the normal
air passages and inside the connective tissue of the peribronchovascular sheaths, interlobular septa,
and visceral pleura secondary to alveolar and terminal bronchiolar rupture. PIE is more frequent in
premature infants who require mechanical ventilation for severe lung disease. Once PIE is
diagnosed, intensive respiratory management is required to reduce mortality and morbidity.
Pathophysiology: PIE often occurs in conjunction with respiratory distress syndrome (RDS), but
other predisposing etiologic factors include meconium aspiration syndrome (MAS), amniotic fluid
aspiration, and infection.
Positive pressure ventilation (PPV) and reduced lung compliance are significant predisposing
factors. However, in extremely premature infants, PIE can occur at low mean airway pressure and
probably reflects increased sensitivity of the underdeveloped lung to stretch. The process of PIE is
initiated when air ruptures from the alveolar airspace and small airways into the perivascular tissue
of the lung.
Infants with RDS have an initial increase in interstitial and perivascular fluid that declines rapidly over
the first few days of life. This fluid may obstruct the movement of gas from ruptured alveoli or airways
to the mediastinum, causing an increase of PIE. Another possible mechanism for entrapment of air in
the interstitium is the increased amount of pulmonary connective tissue in the immature lung. The
entrapment of air in the interstitium may result in a vicious cycle causing compression atelectasis of
the adjacent lung, which then necessitates a further increase in ventilatory pressure with still more
escape of air into the interstitial tissues.