[Dynamic measurement of surface tension versus gas chromatography dipalmitoylphosphatidylcholine analysis of amniotic fluid; a comparison of a bedside method with a highly specialized surfactant analysis].

The diagnosis of fetal lung maturity by analysis of the amniotic fluid still constitutes a present-day problem. In this study the results of measuring the dynamic surface tension by the Wilhelmy-balance were compared with the DPPC (Dipalmitoyl-Phosphatidyl-Choline) and lecithin species-analysis by the quantitative capillary gas chromatography. The first possibility is a "bed-side"-method, which evaluates the effect of the surfactant in the amniotic fluid in its entirety, whereas the second method represents a highly specialized laboratory procedure analysing the most important part of surfactant contact. The surface tension of amniotic fluid is expressed by its value at 20% of the extension of the surface (gamma-min) as well as the hysteresis area. We were able to show a better correlation between the hysteresis area and the DPPC (r = 0.422, p less than 0.012) than between the gamma min and the DPPC (r = 0.370, p less than 0.031). The correlation between the hysteresis area respectively between the gamma-min, and the second gas chromatographically detectable component of the surfactant, PC 30 was not so distinct (r = 0.068, p less than 0.744; R = -0.355, p less than 0.075). Obviously this component of the surfactant is not as active on the surface and therefore not as important. Further we could show, a negative correlation to the lecithin species PC 34; with increasing surface activity and increasing lung maturity this lecithin species quantitatively recedes into the background.