Respiratory Distress Syndrome in Hong Kong

Abstract

In the past, very few new-borns were reported to develop RDS in Hong Kong (unpublished observation). The general impression is, however, that the incidence of RDS has increased during the past decades. The aims of this study were to compare the incidence of RDS in premature babies during the last two decades and also to identify possible risk factors for the development of RDS.

In a retrospective descriptive study the incidence perinatal factors of RDS in premature babies treated in Queen Mary Hospital, Hong Kong was delineated in 1979, 1983 and 1993. The RDS diagnose criteria were: immature lungs, below 37 weeks of gestation, early onset of respiratory distress, respiratory rate >60/mm, subcostal or substernal retractions on inspiration, O2 requirement to abolish cyanosis in room air, blood gases showing acidosis, chest X-ray showing presence of reticulogranular pattern and at post mortem showing hyaline membranes. The control group consisted of infants with a gestational age of 23 to 30 weeks and a birth weight of less than 3000 grams with no diagnosis of RDS. For the three study years a total of 132,162 and 188 hospital records of premature babies were analysed.

The results showed no clear difference in the RDS incidence during these years; 13%, 9% and 15%, respectively. Comparing our results with the results of previous studies we conclude that the incidence of RDS in Hong Kong is similar or slightly lower than the incidence in other parts of the world. The overall mortality due to RDS decreased sharply during the study years. Babies who developed RDS were far more likely (p<0.0001) to die (32%) from RDS than the prematurely born infants without RDS (4%). Being born with a length of gestation below 30 weeks, with a birth weight of less than 1500g, breech delivery and an apgar score below 6 at 5 minutes after birth appeared individually to be associated with an increased risk of RDS. However, when applying a multiple linear logistic model to the series only prematurity remained as a significant risk factor for RDS (odds ratio=1.59).

In summary, the incidence of RDS has not changed during the last 15 decades in Hong Kong but the mortality rate in RDS has decreased substantially. Prematurity remained as the single significant one in a multivariate analysis.