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Pulmonary interstitial emphysema is a condition that can occur in babies who are born prematurely and need artificial ventilation because their lungs are not mature enough to function normally. The air passages in the lungs are divided into smaller and smaller branches, ending in small air sacs called alveoli and, in a premature baby, the pressure of the air being pumped in by a ventilator may cause the smallest tubes, leading to the alveoli, to rip away from their connecting branches. Air then leaks out of the respiratory passages into the surrounding tissues.
As interstitial pulmonary emphysema is more commonly associated with mechanical ventilation, infants with lung diseases and associated breathing difficulties are more at risk for the condition. Respiratory distress syndrome is one such lung disease, found mainly in premature babies. It is caused by the premature infant having a lack of surfactant, the substance that normally covers the alveoli and stops them from collapsing when the baby breathes out. A surfactant replacement can be given, along with artificial ventilation, but, even at low pressures, infant pulmonary interstitial emphysema can occur. This is because the immature lungs may fail to stretch adequately, causing rupturing of the air tubes near the alveoli.
Respiratory distress syndrome can also cause fluid to build up in the tissues around the alveoli, and this can prevent any leaked air from escaping, making the pulmonary interstitial emphysema more severe. The captured air may constrict the lung, making breathing even more difficult and perhaps encouraging medical staff to increase the ventilation pressure, if the condition has not been recognized. This can cause even more air to leak out of the respiratory passages into the tissues, in a worsening cycle of events.
A diagnosis of this condition in neonates, or newborns, usually arises as a result of observations made during ventilation. The condition is suspected if the blood pressure and oxygen levels fall and ventilation becomes difficult, with the baby's condition deteriorating. An X-ray of the chest can be used to confirm the diagnosis and air may be seen to have leaked into small areas in one lung, or it may be spread diffusely throughout a lung, or even through both lungs at once.
Where only one lung is affected by pulmonary interstitial emphysema, infants may be positioned so they are lying on the affected side, effectively pressing down on the air leak and helping to stop it progressing. This means more air is available to keep the other, unaffected lung inflated and breathing. Sometimes the unaffected lung is gently ventilated. If both lungs are affected, ventilation can be carried out using a special rapid, low pressure technique. Although pulmonary interstitial emphysema can be fatal, recent treatment methods have improved the outlook, though survivors are more likely to suffer from lung disease in later life.