ADJUSTMENT OF VENTILATION, INTRAPULMONARY GAS EXCHANGE, AND ACID-BASE BALANCE DURING THE FIRST DAY OF LIFE

Abstract

Determinations of blood gases and of acid-base balance were done in umbilical vein and artery blood at birth and in arterial blood at the age of 20 minutes in 20 infants of diabetic mothers. All were born by cesarean section, 18 of them between 36 and 37 weeks gestation. None showed respiratory distress at any time. Ventilation, gaseous metabolism, functional residual capacity, intrapulmonary gas exchange, and acid-base balance were determined at the age of 1, 4, and 24 hours in these 20 infants. The results indicate the following conclusions with regard to infants of diabetic mothers. 1. Adjustment of ventilation to perfusion in the lung appears to be complete at 4 hours of life. 2. Throughout the first 24 hours there is a persistence of an over-all true right to left shunt of approximately 20-25% of the total cardiac output. The exact localization of this shunt is unknown. 3. Acid-base balance in cord blood and in arterial blood during the first day of life in infants of diabetic mothers differs only slightly from that of infants of nondiabetic mothers. At 1 and 4 hours of age there is some persistence of a slight respiratory acidosis. 4. At 24 hours infants of diabetic mothers have the usual low arterial Pco2 of other newborn infants, but a ventilation equivalent of 16.5, which is normal for adults. 5. Although 6 of the 17 infants studied at 4 hours have shown a respiratory rate above 60 without other signs of respiratory distress, these infants with high rates had small tidal volumes, high physiologic dead-space/tidal volume ratios, and relatively little increase in minute volume.