Development of Localized Pulmonary Interstitial Emphysema in a Late Preterm Infant without Mechanical Ventilation

Pulmonary interstitial emphysema (PIE) is not an uncommon finding in premature infants with respiratory distress who need respiratory support by mechanical ventilation. PIE has been reported in a few cases of neonates in whom either no treatment other than room air was given or they were given continuous positive end-expiratory pressure (CPAP) support. We present a case of a premature neonate who presented with respiratory distress, in whom PIE and spontaneous pneumothorax (PTX) developed while on CPAP therapy only. The patient was treated conservatively with subsequent resolution of the radiological findings and clinical improvement. No surgical intervention was required. It is important to know that PIE may develop independently of mechanical ventilation. We would like to add this case to the literature and describe the pertinent plain film and computed tomography (CT) findings of this entity, the possible mechanism of development, and the differential diagnosis. A review of the literature is also provided. 1. Introduction Pulmonary interstitial emphysema (PIE) is a form of air leak syndrome. It occurs when the air escapes from the small airway or alveolus into the pulmonary interstitium. It dissects along the bronchovascular bundles and radiates outwards to the periphery of the lung to form subpleural blebs. These blebs may burst through visceral pleura into the pleural space resulting in pneumothorax (PTX). The interstitial air can also pass through the lung hilus directly into mediastinum and cause pneumomediastinum. Further grave complications of interstitial air can be pneumopericardium, pneumoperitoneum, subcutaneous emphysema, and terminally massive air embolism [1]. When infants are given positive pressure ventilation, especially but not exclusively by intubation and mechanical ventilation, a continuous pressure ensures passage of air throughout the interstitial lymphatics. The incidence of PIE is high in ventilated low-birth-weight infants, reported as high as 33% in this group by Greenough and others [2–4]. PIE is more common in premature infants with surfactant deficiency treated with respiratory support in the form of mechanical ventilation. The incidence of spontaneous air leak syndromes in premature infants is about 1-2%; many infants are asymptomatic. There are few cases of spontaneous PIE in patients on continuous positive airway pressure (CPAP) [4–7]. We wish to add an additional report of a late preterm infant who developed localized pulmonary interstitial emphysema within the right lung, in association with PTX and