Oronasopharyngeal suction at birth: effects on arterial oxygen saturation.

The effect of oronasopharyngeal suction (ONPS) on arterial oxygen saturation (SaO2) is described in a controlled study of 30 normal term newborn infants. In 15 of them, ONPS was performed immediately after birth. The SaO2 value was recorded through a pulse oximeter. The ONPS group had a significantly lower SaO2 between the first and the sixth minutes of life and took longer to reach 86% and 92% saturation. According to this study, ONPS should not be performed as a routine procedure in normal, term, vaginally born infants.

Phosphatidylglycerol determination in the amniotic fluid from a PAD placed over the vulva: a method for diagnosis of fetal lung maturity in cases of premature ruptured membranes.

Four hundred and forty seven pregnant women with ruptured membranes, were prospectively studied in order to assess the diagnostic capacity of Phosphatidylglycerol (PhG) determination in amniotic fluid recovered from vulval pads in the diagnosis of Hyaline Membrane Disease (HMD). The identification of PhG was performed using one dimensional silica gel thin layer chromatography. The sensitivity of PhG determination in the diagnosis of HMD in newborns of the total population was found to be 88.2%, with a specificity of 76.9%. In the study population, the incidence of HMD was 7.6%, the negative predictive value was 98.8% and, the positive predictive value was 24.0%. When the 265 newborns of the gestational age group of less than or equal to 34 weeks is considered, we observed an incidence of HMD of 12.1%. The diagnostic capacity of PhG in this group was shown by a sensitivity of 87.5%, a specificity of 76.4%, a positive predictive value of 33.7% and a negative predictive value of 97.8%. This method of assessment of fetal lung maturity has a diagnostic capability similar to that described by other authors, who used amniotic fluid obtained vaginally or transabdominally. The procedure described here of amniotic fluid collection is non-invasive, harmless to the mother and fetus and simple to perform. The characteristics of this method, allow serial studies of the amniotic fluid to be carried out.

Oxygen transport in newborns at different gestational ages.

Oxygen (O2) transport was assessed through the affinity between O2 and hemoglobin (Hb) in 123 newborns of 28 to 40 week gestational ge, with a minimum of 9 newborns for each gestational age group (see table). In order to assess the O2-Hb affinity, we studied the correlation between the pO2 and the Hb saturation for each gestational age, obtaining estimates of the oxy-hemoglobin dissociation curves corresponding to each gestational age (see fig. 3). The pO2 levels corresponding to the 50% saturation (P50) for each gestational age were estimated from there. All newborns were from single vaginal deliveries with no fetal distress before birth and with an adequate weight for gestational age. The latter was calculated according to the date of the last menstrual period (78% of the cases), echography (10.6% of the cases) or neonatal physical exam (11.4% of the cases). A P50 vs. gestational age linear regression showed a high determination rate (r2 = 0.957, p less than 0.00001) (see fig. 2) which supports the hypothesis of the P50 linear growth; decrease in the Hb-O2 affinity with increasive gestational age (Hb-O2 affinity is different in newborns of different gestational ages). With these results one may conclude that the Hb-O2 uptake varies according to gestational age (P50 changes linearly as gestational age increases) and that a single measurement of pO2 in a newborns, blood does not accurately evaluate the amount of O2 that is transported to the tissues, because the transport capacity depends, among other factors, upon gestational age. The Hb saturation better represents the amount of O2 that can get to the cell level.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of pulmonary dynamics in normal newborns: a pneumotachographic method.

A pneumotachographic method for assessment of pulmonary dynamics in critically ill newborns in an intensive care setting was developed in our laboratory. Before the results obtained with this method could be applied, the normal range of values were determined in 48 normal term and preterm newborns. Their body weight ranged between 1200 and 4100 g, and postnatal ages between 24 hours and 21 days. In three infants, two determinations were performed after an interval of 7 days. The studies were performed with a pneumotachograph applied to the upper airway by means of an inflatable face mask or latex nasal prongs. The air flow signal was electronically integrated to time to produce a volume signal. Airway pressure was determined proximal to the pneumotachograph. Esophageal pressure was determined with a water filled catheter placed in the lower third of the esophague. Tidal volume (VT), minute ventilation (V), Dynamic compliance (Cdyn), total pulmonary resistance (R), total pulmonary work (Wt), Elastic work (We), and flow resistive work (Wv), were determined. A significant linear correlation was found between Cdyn and body weight (r = 0.50, p less than 0.01) whereas no significative correlation was found between body weight and VT, V or R. Values for VT, V and Cdyn were corrected for body weight and means (X), standard deviation (SD) so as 10th and 90th percentiles are shown in table III. X, SD and percentiles for R were shown in table III. Wt, We and Wv were corrected for V, and X, SD and percentiles shown in table III. Values of VT/Kg, Cdyn/Kg and R are similar to those found by other authors with pneumotachography and plethysmography. The V/Kg values obtained by us were higher than those reported by other authors, which together with the lack of correlation of VT and V with body weight, question the reliability of V values in our study. This could be explained by: 1) excessive increase in dead space in cases in which a face mask was used; 2) nocioceptive stimulus produced by face mask or nasal prongs; 3) inadequate selection of the moment at which the record was obtained. Whichever the explanation, our values of V cannot be considered as basal, and should be interpreted with caution. The results obtained allow us to continue with our program and apply this method to the study of newborn infants with RDS.