Robert C. Borer

Diagnosis of the respiratory distress syndrome by amniocentesis

Abstract Studies on 302 amniocenteses show that changes in phospholipids in amniotic fluid (PLAF) reflect those in the lung of the developing fetus. A sudden increase in lecithin concentration after 35 weeks heralds maturity of the pulmonary alveolar lining when respiratory distress syndrome will not occur should the fetus then be born. Clinical interpretation is made on a thin-layer chromatogram by inspection; a lecithin spot clearly larger than that of sphingomyelin marked pulmonary maturity in the fetus.

The interpretation and significance of the lecithin/sphingomyelin ratio in amniotic fluid

Abstract The significance of the lecithin/sphingomyelin (L/S) ratio is well established. However, numerous variations in techniques are appearing, and certain issues about techniques have emerged; among these, acetone precipitation, phosphorus determination rather than densitometry or area measurement, measurement of total phospholipids rather than the L/S ratio, and determination of lecithin concentration rather than the L/S ratio are discussed. Acetone precipitation allows examination of the physiologic (surface-active) fraction of lecithin; this fraction also helps to evaluate the rapidly maturing lung and possibly prevent false predictions. Maturational acceleration of the L/S ratio may be secondary to chronic stress or to acute stress such as acute placental infarction or ruptured membranes. Further evidence is presented that there is continuity between the fetal lungs and amniotic fluid. General principles are presented as a guide in clinical interpretation of the L/S ratio.

Postmortem gas accumulation in premature infants.

Serial postmortem radiographs were taken of 22 infants with the idiopathic respiratory distress syndrome. All had umbilical artery catheters and had received intermittent positive pressure ventilation prior to death. Four of the 22 gave evidence of spontaneous gas accumulation within intravascular, intraperitoneal, and cerebrospinal fluid spaces. In three, gas accumulation was demonstrated within 25 minutes after death and progressively increased even though their umbilical catheters were removed immediately after death. Since physiologic gas accumulation can occur rapidly, the significance of postmortem intravascular gas can be interpreted only if the interval between death and the radiographic exposure is known.

Tracheal aspirate lecithin/sphingomyelin ratios as predictors of recovery from respiratory distress syndrome

In thirty infants with severe respiratory distress syndrome who required endotracheal intubation, serial tracheal aspirate lecithin/sphingomyelin ratios were determined. There was 19 survivors and 11 nonsurvivors. The L/S ratios were plotted as a function of postnatal age; the ratios of the survivors demonstrated a significant increase between 24 and 96 hours. Nonsurvivors did not show this change. There was a significant difference on Days 3, 4, and 5 between survivors and nonsurvivors in the percentage of L/S ratios greater than 2.5. Daily mean L/S ratios correctly identified the outcome of 23 of 24 infants alive on Days 4 and/or 5 and were a more accurate prediction of survival than a single L/S ratio. The changes in the L/S ratios of the tracheal aspirates were not related to gestational age.

ACCURACY OF GASTRIC ASPIRATE LECITHIN/SPHINGOMYELIN RATIO AND CHEST ROENTGENOGRAM IN THE DIAGNOSIS OF RDS

Gastric aspirate (GA) lecithin/sphingomyelin ratios (L/S) and chest roentgenograms (CR) obtained in the first 24 hrs. of life in 87 infants with respiratory symptoms were analyzed independently. CR diagnosis was made separately by three pediatric radiologists in three categories: definite RDS (D), absent RDS (A) and equivocal of RDS (E). Clinical diagnosis was made in 87 patients (histological confirmation in 19): 34 infants had RDS and 53 had other respiratory problems.The agreement in CR interpretation by the radiologists was tested for the various categories D, E and A by Chi2 analysis and found to be highly significant, p < .0005. The correlation of the CR diagnosis and clinical RDS, the correlation of GA L/S < 2.5 and clinical RDS, the correlation of the CR category D and the GA L/S < 2.5 and finally the correlation of the CR category A and the GA L/S > 2.5 were all significant by Chi2 analysis, p < .0005.This report documents the accuracy of both CR and GA L/S when obtained in the first 24 hrs. of life as highly reliable studies for both the diagnosis and exclusion of RDS.

Failure of serial chest radiographs to predict recovery from respiratory distress syndrome

Chest radiographs of 29 patients with the clinical and radiographic diagnosis of RDS during the 5 days of the illness were graded according to a modification of the classification of Bomsel. There was no significant difference between the radiographs of surviving neonates and those who died of RDS. Mean L/S ratios were also collected from 26 of the 29 patients. Those who survived had significantly more mean L/S ratios greater than 2.5 than did the nonsurvivors (p less than 0.01). This difference did not correlate with the staging of the chest radiographs. The mean L/S ratio is a better predictor of survival than chest radiographs during the first 5 days of RDS.

CHOLINE INCORPORATION INTO LECITHIN IN RESPONSE TO INSULIN OR DEXAMETHASONE IN HOMOGENEOUS CELL CULTURES OF RAT LUNG EPITHELIAL CELLS AND FIBROBLASTS

Summary: Labeled choline incorporation into adult rat lung type II alveolar epithelial cells and adult rat lung fibroblasts in monolayer culture was dgtennined after incubation with insulin (Ins) 10 μg/ml. Dexamethasone (Dex) 10-6 M, or no drug (ND). Incubation periods were 1. 3. 4, and 5 hours. The lecithin (phosphatidyl choline - PC) recovered was separated into disaturated phosphatidyl choline (DSPC) and unsaturated phasphatidyl choline (USPC). Results expressed as specific activity per hour (see Table) indicate that the incorporatian of choline into PC and USPC was greater in fibroblasts (F) than in epithelial cells (E) whether ND, Dex or Ins was present. For incorporation into DSPC, there was no difference between E and F whether ND, Dex or Ins was present. There was significant increase in choline incorporation into PC or USPC for both cell types when Ins was present, whereas there was no difference for either cell type when Dex was present. Insulin significantly increased choline incorporation into DSPC in E cells only. Dex was no different from ND in DSPC incorporation in either cell type. We attribute the greater lecithin synthesis of the F cells to a more rapid increase in cellular strucrural lipids in the fibroblast cell. Dex had no effect an either cell type from the short-term exposure or possibly because the effect of dexamethasone on alveolar epithelial cells is mediated by product(s) from other lung cells. and thus requires a mixed cell culture to have its effect. We suggest that further study of isolated homogeneous cell lines vill not be fruitful in the evaluation of mechanisms of acceleration of lung maturation.Speculation: Isolated alveolar epithelial cells shw a relatively greater increase in DSPC synthesis than do isolated fibroblasts in response to insulin. while neither cell type responds to short term glucocarticoid treatment. Since other investigators using mixed lung cell cultures have sham increased DSPC in response to insulin end even greater response with glucocarticoid treatment, it is likely that the presence of fibroblasts or other pulmonary cells is required for the alveolar epithelial cell to increase DSPC production in response to glucocorticoids.

TRACHEAL ASPIRATE (TA) LECITHIN SPHINGOMYELIN RATIO (L/S) AND RECOVERY FROM RDS

Previously we have demonstrated that changing TA L/S were associated with survival from RDS. In this current report L/S of serial TA obtained during the first 120 hrs. of life were examined in 30 infants with severe RDS requiring endotracheal intubation. The infants were divided into two groups by survival: survivors (S), n=19; non-survivors (NS), n=ll. The means of all L/S values per day in infants with at least three samples per 24 hr. period were calculated. In S 10/14 (71%), 10/12 (83%) and 9/9 (100%) infants had mean L/S > 2.5 on days 3, 4 and 5 respectively. In NS 1/5 (20%), 1/6 (17%) and 1/7 (14%) infants had mean L/S > 2.5 on days 3, 4 and 5 respectively. This difference was significant by day 4 (p < 0.05). Both S and NS were similar in their requirement for ventilatory support at 48 and 72 hrs. of life. At 96 and 120 hrs. there were significantly fewer S requiring mechanical ventilation. Thus, the attainment of a TA L/S > 2.5 by day 4 appears to be a chemical predictor of survival in infants with severe RDS.A significant observation in this study was that the attainment of a TA L/S > 2.5 on day 4 was independent of gestational age. This observation suggests that TA L/S is related to postnatal factors.

484 EVALUATION OF A REGIONAL PERINATAL EDUCATION PROGRAM FOR HEALTH PROFESSIONALS

A modular, self-paced instructional program in neonatal respiratory distress was provided to all levels of health professionals and evaluated for its ability to cause cognitive change. The program consisted of 30 media packages (video-tape and slide-tape) and a study guide. Local hospital personnel in 3 communities were responsible for dissemination of the program to 187 potential participants. 63% of the MDs, 73% of the RNs and 64% of the LPNs completed eight or more of the packages. Cognitive change was assessed by written tests administered before and following presentation of the study materials in the community hospitals.All professional groups demonstrated a gain in cognitive level Score differences between pediatricians and obstetricians on pediatric care and obstetric care were significant (p<.05) in the pretest but no differences were found in the post-test. This community-based educational program was effective in increasing the cognitive level of learners representing wide differences in professional background. Changes in care were documented in the hospitals as a result of this program.

Diagnosis of the respiratory distress syndrome (RDS) by the absence of phosphatidyldimethanolamine (PDME) in tracheal efluents of low birth weight (LBW) infants

PDME, an intermediate in the synthesis of surfact-active lecithin from lungs, was isolated from lipid extracts of tracheal effluent (“mucus”) obtained from hypopharynx, separated by thinlayer chromatography on precoated silica gel mylar strips and detected with bromothymol blue.PDME, arterial blood pH and rectal temperature were recorded seriall (½, 1, 2, 3, 4 hours of life) in 28 randomly selected LBW infants. Of 126 tests performed, the results at 3 hours correlated with diagnosis of RDS. PDME was absent in 14/16 infants with RDS, and PDME was present in 11/12 infants without RDS. There was a significant (p < 0.01) association between arterial blood pH and PDME:Little correlation was found between temperature and PDME. The results indicate that serial determinations of PDME may provide a rapid definite early chemical diagnosis of RDS.