THE COURSE OF THE RESPIRATORY DISTRESS SYNDROME OF NEWBORN INFANTS. AS INDICATED BY POOR STABILITY OF PULMONARY EXPANSION.

Until recently most investigators of the pathology of the respiratory distress syndrome (RDS) gave prominent consideration to the two pulmonary changes which could readily be ascertained a t autopsy: atelectasis, and hyaline membranes (HM). More recently another pulmonary factor was found to be regularly associated with the RDS, namely, poor stability of lung expansion (PS) caused by a deficiency in the peculiar surface activity of the lining layer of the respiratory surfaces. Data from autopsy material pertaining to these factors have now accumulated in sufficient numbers to suggest an interpretation of the pathogenesis and course of the pulmonary disturbance in the RDS which will be presented here. Since we will be concerned with the incidence of HM and PS in relation to each other and to birth weight and length of survival, the concepts currently associated with these two conditions will a t first be briefly reviewed.