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Congenital tracheal occlusion, though seemingly rare, is generally fatal if not attended to immediately. A high index of suspicion should help to make the diagnosis in a neonate when there are respiratory distress at birth and no audible cry and an endotracheal tube cannot be advanced beyond the vocal cords. We present our experience with cases of congenital tracheal obstruction due to various causes during a period of four years.

Chloral hydrate has been used clinically for over 100 years. There is significant paucity of information regarding chloral hydrate metabolism in neonates and infants. Chloral hydrate and its various metabolites were quantitated in 12 neonates and 2 infants at prescribed time intervals. The analysis of the data indicates accumulation of trichloroacetic acid and trichloroethanol in tissue of compromised infants. There is indirect evidence of competition for hepatic glucuronidation for bilirubin with trichloroethanol in ill preterm infants. Multiple dosing of chloral hydrate in preterm infants should be used with caution and frequent monitoring of serum bilirubin concentrations is indicated in such cases. The mechanism of chloral hydrate metabolism is discussed in detail.

General anaesthetic techniques continue to be used for Caesarean section despite the possible increased incidence of foetal acidosis and neonatal depression. Two techniques of general anaesthesia (methoxyflurane-oxygen and nitrous oxide-oxygen) and lumbar epidural anaesthesia were compared in 37 patients under-going elective Caesarean section. Apgar scores at birth were similar in all three groups. Neurophysiological testing of the neonates at six hours and twenty-four hours of age revealed a superiority for the methoxyflurane-oxygen and lumbar epidural techniques, although the babies in the epidural group tended to be hypotonic. Cord blood gas analysis showed the babies in the methoxyflurane group to have a higher PaO2 with less metabolic acidosis than the babies from the other two groups. The maternal effects of the three anaesthetic techniques were similar, with only a small rise in serum fluroide levels noted in the methoxyflurane group.

The effect of sudden and sustained lung inflation on inspiratory time (Ti), expiratory time (Te) and duration of apnea, as a translation of the Hering-Breuer reflex, has not been systematically analyzed in preterm infants. To examine such effects, 10 infants (body weight 1,550 ± 110 g; gestational age 31 ± 1 weeks) were studied. Lung inflation was obtained by applying negative pressure around the chest using a negative pressure incubator. After a control period, lung volume functional residual capacity was increased by an average of 14, 23, 34 and 53%. During lung inflation, Ti, Te, total respiratory cycle duration, incidence and duration of apnea increased. Minute ventilation decreased due to a decrease in frequency. Tidal volume decreased but not significantly. Inspiratory and expiratory flows decreased. These results (1) confirm the presence of the Hering-Breuer reflex in preterm infants, as reflected by increased Te and appearance of apnea during lung inflation; and (2) show that contrary to expectations, Ti increased significantly with lung inflation.

In an attempt to prove whether beta-endorphin diurnal rhythm existed in neonates, 17 infants with a mean (+/- SD) gestational age of 31.7 +/- 4.8 weeks and a birth weight of 1,790 +/- 898 g were studied at a mean postnatal age of 3.3 +/- 0.5 days. Plasma samples were obtained from a pre-existing umbilical arterial line at 09.00 h, noon and 15.00 h. Mean plasma concentrations of beta-endorphin were 68.3 +/- 27.7, 54.5 +/- 13.7, and 45.1 +/- 10.8 pg/ml, respectively. Highly significant (p = 0.0002) variation of plasma beta-endorphin concentration was observed in these neonates suggesting the presence of a diurnal rhythm of beta-endorphin in neonates. It is important to specify the time of collection of blood samples for determination of opiates in neonates.

Summary: The differences in the immediate (30 sec or l min) and late (5 min) ventilatory response to high and low O2 have not been quantitated in preterm infants and adult subjects using the same methods. It was thought that these differences might explain the paradoxical ventilatory response to CO2 at various O2 concentrations in preterm infants (12). Thus, 9 preterm infants and 10 adult subjects were given 21% O2 to breathe and then 100 or 15% O2 for 5 min each. Adults also breathed 15% O2 before 100% O2 or 12% O2 in order to make their resting arterial PO2 more comparable to those of infants breathing 21% O2. The ventilatory response to 100% O2 was the same in preterm infants and adult subjects, but the late response to 15% O2 remained paradoxical, ventilation decreasing at 5 min by 18% in infants and increasing by 19% in adults. The authors conclude: 1) the traditional concept of the ventilatory response to 100% O2 being different in infants and adult subjects is false; 2) the notion that the response to low O2 is paradoxical in infants is correct; and 3) the data do not explain why the response to CO2 under various background concentrations of O2 in infants is the reverse of that in adult subjects, but the depressed ventilatory response to hypoxia in infants may justify, at least in part, their flatter response to CO2 during low O2 breathing. Speculation: The findings suggest that the response of preterm infants to high and low O2 per se is not the cause of the paradoxical response to CO2 under various background concentrations of O2. If it were, it would be expected that the response to low and high O2 would differ in infants and adults. This was true for hypoxia only, the response to hyperoxia being the same in infants and adults. The speculation, therefore, is that differences in cerebral blood flow caused by CO2 and O2 interaction may be responsible for the paradoxical response to CO2.

Systolic time intervals were measured from simultaneous high speed recordings of the electrocardiogram, phonocardiogram, and carotid artery pulse in 15 men with chronic severe anaemia not in heart failure and with a normal heart size, and in 15 normal men. Heart rates, electromechanical systole (QS2), pre-ejection period index (PEPI), left ventricular ejection time index (LVETI), and the ratio of pre-ejection period to left ventricular ejection time (PEP/LVET) did not differ significantly in the two groups. After the intravenous administration of frusemide in 10 of the anaemic patients, the pre-ejection period index was prolonged, the PEP/LVET ratio increased, heart rate increased, and the left ventricular ejection time index shortened. Intravenous digoxin did not alter the QS2 interval and heart rate significantly in the anaemic subjects. Left ventricular function in chronic severe anaemia as measured by systolic time intervals does not differ from that of normal controls. The effect of frusemide on the systolic time intervals is explained as an effect of the fall in preload, bringing cardiac function further down on the ascending limb of the Frank-Starling curve. Other related studies are discussed.

The overall objectives of this research program were to determine the source of brittleness in Al-Li alloys, determine ductility enhancement through slip homogenization effected by grain refinement and incoherent dispersoids, compare the properties of Al-Li alloys prepared from different types of rapidly solidified powders with the properties of cast Al-Li alloys and other commercial high-strength Al alloys, and identify and recommend for further development promising Al-Li alloy compositions for use in aircraft structures. The approach followed was that of rapid solidification and powder-processing, which result in significant microstructural refinement and make possible the processing of novel Al-Li alloy compositions not amenable to ingot-casting methods.

Two cases with unusual primitive foregut anomalies are described. Both children, born within 24 hours of each other, had complete tracheal atresia, proximal esophageal atresia, and distal tracheoesophageal fistula along with some minor anomalies; both needed immediate tracheostomy for adequate ventilation. At 15 months of age, both patients are thriving and developing normally with the exception of their speech. A review of the literature revealed no other survivors with this condition. Diagnosis of tracheal atresia should be kept in mind when a newborn infant exhibits respiratory distress without an audible cry associated with failure to advance the endotracheal tube beyond the vocal cords. An immediate tracheostomy can be lifesaving in these children.

A two-year-old child dying of pulmonary hypertension and cor pulmonale secondary to bronchopulmonary dysplasia, was demonstrated to have reactive pulmonary hypertension in response to 100% oxygen and isoproterenol infusion. In an attempt to find an oral medication to maintain pulmonary vasodilatation, experimental trials were done using hydralazine, salbutamol, nifedipine and diltiazem. Cardiac index, pulmonary and systemic vascular resistances and intrapulmonary shunts were monitored during the trials. Hydralazine, salbutamol and nifedipine were ineffective. Diltiazem 2.0 mg given every 6 h resulted in a profound and sustained decrease in pulmonary pressures and resistance, and a reversal of the cor pulmonale.

The physiological and biochemical status of two groups of neonates with patent ductus arteriosus (PDA) requiring surgical ligation were compared. One group (n = 14) had ductus ligation in the operating room (OR) and the other group (n = 14) had the same operation in an isolation room in the Neonatal Intensive Care Unit (NICU). The groups were closely matched in terms of gestational age and weight. Nursing time and disposable equipment savings were significantly different. We have confirmed that PDA ligation can be done safely in the NICU and is more cost efficient than ligation in the OR.

Improvements in both care and technology have led to the survival of more low birthweight infants. Initially, these infants are not fed orally and are placed on parenteral nutrition. In an attempt to evaluate sequential time-wise changes in gastric pH and occult blood loss, evaluation of gastric pH and tests for the presence of blood in the gastric aspirate were carried out in two groups of infants. Group 1 consisted of seven cases, three males and four females, with a mean +/- SE gestation of 29.9 +/- 0.8 weeks and a birthweight of 1410 +/- 190 g. Group 2 consisted of nine cases, three males and six females, with a mean +/- gestation of 28.6 +/- 0.84 weeks and a birthweight of 940 +/- 120 g. Gastric contents were sampled through indwelling orogastric tubes every 4-6 h daily for the first seven days in Group 1 and 14 days in Group 2. Infants in Group 1 were spontaneously breathing with mild hyaline membrane disease (HMD) whereas Group 2 infants had severe HMD requiring ventilation. Results indicate that critically ill preterm infants (Group 2) had significantly lower pH when compared to Group 1 (p less than 0.015). Progressive decrease in pH was observed in both groups (P less than 0.001). The association of occult gastric blood loss with decreasing pH was examined using pooled data from both groups of neonates. During the times when bleeding occurred, the mean +/- SE gastric pH level was 2 +/- 0.1.(ABSTRACT TRUNCATED AT 250 WORDS)

Using noninvasive measurement of cranial blood flow, we previously demonstrated that full-term asphyxiated neonates have decreased cerebral perfusion that can persist up to 5 days of age. In an attempt to test their postischemic cerebrovascular CO2 reactivity, we measured cranial blood flow in ten asphyxiated term (39 +/- 0.8 weeks and 3078 K 400 gm) infants with and without inhaled carbon dioxide (3 percent). The end tidal CO2 (PaCO2) increased significantly, from 28.8 +/- 1.0 mm Hg to 32.3 +/- 2.0 mm Hg after CO2 inhalation (p less than 0.01), whereas the cranial blood flow showed no significant change (38.5 +/- 5.0 ml/min/100 gm brain weight to 37.6 +/- 6.0 ml/min/100 gm brain weight). We conclude that term infants with hypoxic-ischemic encephalopathy have low cranial blood flow at 3 days of age. Their cerebrovascular response to inhaled CO2 is variable and suggests some impairment.

Rapid solidification of a molten, multicomponent alloy against a metallic substrate promotes greater microstructural homogeneity and greater solid solubility of alloying elements than can be achieved by slower-cooling casting methods. The supersaturated solid solutions produced by rapid solidification can be subsequently annealed to precipitate, by controlled phase decomposition, uniform 10-100 nm precipitates or dispersoids. TEM studies were made of the precipitation of metastable Al3Li(δ’) and equilibrium AL3H phases and the deformation characteristics of a rapidly solidified Al-3Li-0.2Ti alloy.

Binary Al-Li alloys containing 1.5-3.0 wt% Li are hardened by precipitation of the metastable, coherent δ' (Al3Li) phase having an Ll2 type crystal structure. Plastic deformation in these alloys occurs by the shearing of δ' precipitates by glide dislocations, resulting in the formation of planar slip bands and therefore stress concentrations at grain boundaries and slip band intersections. These stress concentrations become potential crack nucleation sites in the early stages of deformation.

Al-Li-Cu alloys combine high specific strength and high specific modulus and are potential candidates for aircraft structural applications. As part of an effort to optimize Al-Li-Cu alloys for specific applications, precipitation in these alloys was studied for a range of compositions, and the mechanical behavior was correlated with the microstructures.Alloys with nominal compositions of Al-4Cu-2Li-0.2Zr, Al-2.5Cu-2.5Li-0.2Zr, and Al-l.5Cu-2.5Li-0.5Mn were argon-atomized into powder at solidification rates ≈ 103°C/s. Powders were consolidated into bar stock by vacuum pressing and extruding at 400°C. Alloy specimens were solution annealed at 530°C and aged at temperatures up to 250°C, and the resultant precipitation was studied by transmission electron microscopy (TEM).The low-temperature (≲100°C) precipitation behavior of the Al-4Cu-2Li-0.2Zr alloy is a combination of the separate precipitation behaviors of Al-Cu and Al-Li alloys. The age-hardening behavior at these temperatures is characteristic of Guinier-Preston (GP) zone formation, with additional strengthening resulting from the coherent precipitation of δ’ (Al3Li, Ll2 structure), the presence of which is revealed by the selected-area diffraction pattern (SADP) shown in Figure la.

Traditionally the Hering-Breuer reflex has been assessed by the presence and length of apnea and/or prolongation of expiratory time (Te) during sustained lung inflation. In recent years a decrease in inspiratory time (Ti) during lung inflation has also been suggested as an indicator of the inflation reflex. Both Te and Ti have not been analyzed systematically in neonates with stratified increase in lung volume. We decided, therefore, to examine the effects of sudden and sustained lung inflation on Ti, Te , and duration of apnea in preterm infants. Ten babies (G.A. 31±1 wk; B.W. 1500±110g) were studied. Lung inflation was obtained by applying negative pressure around the chest using a negative pressure incubator. Response time of the system was less than .3 sec. After a control period, we increased lung volume (FRC) by 15%, 25%, 35%, and 60%. We measured Ti, Te, apnea and FRC before and during lung inflation. We found a significant increase in Ti, Te, and duration of apnea with an increase in FRC by as little as 15% (p

The inhalation of 100% O2 for more than 30 sec increases minute ventilation (VE) in neonates. To discover whether this hyperventilation is due to cerebral vasoconstriction and brain ischemia we measured VE, alveolar PCO2 (PACO2) and CSF PCO2, PO2, pH and bicarbonate before and after the administration of 100% O2. Subjects were 7 neonates (G.A.±.S.E. 38±1.4 wks; B.W. 3,354±.370 gm; P.N.A. 3.8±1.9 days) who were being worked up for sepsis. VE was measured with a noseplece and a screen flowmeter. CSF samples were taken before and 7 min after continuous breathing of O2. Results: All values: Mean ± S.E. These findings suggest that hyperventilation with 100% O2 is associated with a decrease in alveolar and CSF PCO2 and a tendency for CSF pH to increase. If central tissue ischemia were present, we would expect CSF PCO2 to increase and pH to decrease. Because they change in the same direction as arterial PCO2 and pH are known to change, the hypothesis that 100% O2 stimulates breathing by producing central ischemia is untenable.