Oxygen therapy in the newborn

Serial determinations of oxygen profiles in infants with respiratory distress

Serial oxygen profiles were determined for 20 newborn infants by measuring arterial tensions at low (20--40%), intermediate (60--80%), and high (95--100%) levels of inspired oxygen. These points were plotted on a graph which estimated the percentage of venous admixture at any particular level of inspired oxygen. The infants' oxygen profiles were then determined. As much as 25% of venous admixture could be attributed to the presence of diffusion and distribution abnormalities in infants with hyaline membrane disease. A substantial number of infants showed increased shunting at high levels of oxygen, even in the presence of continuous distending airway pressure. It is hypothesised that a rising shunt is due to complete absorption of gas in poorly ventilated alveoli at high concentrations of inspired oxygen, resulting in the presence of atelectasis and redistribution of blood to poorly ventilated areas.

Prognosis for infants with idiopathic respiratory distress syndrome

Infants with the idiopathic respiratory distress syndrome admitted to the intensive care unit during January 1972 to September 1974 were reviewed. The overall mortality rate for infants whose birth weight was 1000 g or more was under 10%, and for those who established spontaneous respiration after birth it was less than 5%. The hyperoxia test was not a useful guide to prognosis. It was possible on the basis of the infants' ability to establish spontaneous ventilation after birth to divide them into two groups. In those who established adequate ventilation the mortality rate was 4-5%; in those who did not it was 57%. This test should be generally applied, since not only does it give an immediate guide to the severity of the disease, which is better than that provided by birth weight, gestational age, or the hyperoxia test, but it may be applied to infants born in and outside a hospital providing neonatal intensive care. Improvement in the outlook for infants with a bad prognosis will be achieved only by improvements in perinatal care designed to minimize severe intrapartum asphyxia in infants of low birth weight.

Use of a continuously recording intravascular oxygen electrode in the newborn

The use of a continuously recording intravascular Po₂ electrode is described. The electrode, based on the Galvanic principle, is built into the tip of a French gauge (FG) 5 umbilical arterial catheter. Its use has considerably improved the management of oxygen therapy in the seriously ill premature newborn infant and has done so with at least a 50% reduction in the amount of blood needed to be removed for gas analysis.

Distending pressure in infants with respiratory distress syndrome

The application of distending pressure to 40 babies with the respiratory distress syndrome (RDS) is described. Pressures greater than 10 cm H₂O were rarely used. On starting distending pressure, considerable improvements in blood gases occurred in all but 4 babies, 2 of whom had pneumothoraces and the other rapidly deteriorated and died from an intraventricular haemorrhage shortly afterwards. In 27 babies the distending pressure was applied for hypoxaemia during the course of the disease. 16 survived without further intervention, though one case eventually required long-term continuous distending pressure (CDP) for pulmonary oedema. 11 out of the 27 required intermittent positive pressure ventilation (IPPV), with 6 survivors. In 13 other babies who had not received CDP previously, the technique was used to assist weaning from IPPV. It sustained oxygenation in each case, and 12 of these babies survived. Seven babies developed pneumothoraces and 2 babies intrapulmonary cysts. 6 babies died, 3 with pneumothoraces. The overall incidence of intraventricular haemorrhage was 3 proven and 2 suspected cases. There was no evidence that distending pressure in any form increased the incidence of intracranial haemorrhage.

The management of respiratory failure in infancy

The management of respiratory failure in infancy has altered considerably over the past two decades, due both to an increasing understanding of the underlying pathophysiological mechanisms involved and the development of new techniques of treatment. This paper outlines the rationale, indications, and details of the therapy which may be required in neonates and infants suffering from illnesses affecting respiratory function.

Serial determinations of blood lactate in respiratory distress syndrome

Blood lactate was measured 4-hourly in 21 newborn babies with respiratory distress syndrome, of whom 13 survived and 8 died. In general, lactate levels were higher in babies who died than in survivors, but there were inconsistencies which were uninterpretable if only a single estimation were made in a baby. Analysis of serial determinations showed that all patients in whom the lactate level never exceeded 35 mg/100 ml survived, and babies with high but falling values also did well. Only those who had rising lactate values, even if initially normal, died. In most cases a high or normal P_ao₂ was associated with normal or decreasing lactate level; but babies with P_ao₂ below 60 mmHg had often also normal or decreasing lactate levels. Some babies had high and increasing lactate levels despite having normal P_ao₂. In order to use lactate levels for prognosis in respiratory distress syndrome (RDS) serial determinations are required. It is concluded that there may be a wide range of hypoxaemia without oxygen deficit in body tissues, so that it is not possible to define a `lower acceptable P_ao₂' which will define adequate tissue oxygenation.

Retinal vasoconstriction in premature infants with increased arterial oxygen tensions

Retinal vessels of newborn and premature infants were photographed under conditions of increasing arterial oxygen tension and the changes in vessel diameter were measured. In 6 infants studied, there was a consistent pattern of vasoconstriction with rise in P_ao₂. The reduction in calibre could be measured, but was not detectable by viewing the retina, unless photographs taken at low and high P_ao₂ were viewed side by side. Frank retinal vasospasm did not occur even at a P_ao₂ of 250 mm. Hg. It was concluded that ophthalmoscopy did not provide an alternative to direct frequent measurement of P_ao₂ in premature infants receiving oxygen therapy.

Apnoea after THAM administration in the newborn

The use of THAM in the treatment of neonatal acidaemia is surveyed over a 3-year period. Of 100 babies to whom the drug was given while they were breathing spontaneously, 17% had respiratory depression during, or within two minutes of injection. If only potentially viable babies are considered, the incidence of respiratory depression increases to 20% and the incidence in babies with respiratory distress is 17%. No single group of babies was particularly susceptible to this action of THAM, except those who had had a previous spontaneous apnoeic attack. No babies became apnoeic after the injection of sodium bicarbonate. It appears that in the 'good prognosis' group according to the hyperoxia test those babies who require correction of their pH have a higher death rate than those who do not. There was no statistically significant increase in the death rate of babies who deteriorated after THAM, but several of these babies only survived after treatment with artificial ventilation. There was an increased incidence of intraventricular haemorrhage in those babies who received 7% THAM rather than 3·60% THAM, but this may be due to other factors in their illness.