The relationship of pulmonary interstitial emphysema to subsequent type of chronic lung disease

Chronic lung disease of prematurity (CLD) can be classified using the chest radiograph taken on day 28 into type 1 (homogeneous opacification) or type 2 (the presence of cystic change) and it has been suggested that the presence of pulmonary interstitial emphysema (PIE) leads to the development of type 2 CLD. To further study this relationship we examined the chest radiographs taken on days 1-7, 14, 21 and 28, of 202 infants treated at Liverpool Maternity Hospital between January 1980 and December 1989 who developed CLD. 39% (54/137) of infants who developed type 1 CLD had suffered from PIE compared with 78% (51/65) with type 2 CLD (p < 0.001). There was no difference in the incidence of PIE in infants who developed CLD and subsequently died compared with those who survived. In the infants who survived there was no significant difference in length of oxygen dependency between those who suffered from PIE (median 99 days oxygen dependent) and those who had no PIE (median 105 days). We conclude that the presence of PIE is associated with subsequent development of type 2 CLD but is not a prerequisite for this radiographic type of chronic lung disease. Of those infants who survive to develop CLD, the presence of PIE does not alter prognosis in terms of duration of oxygen dependency or mortality.