Case 3: Hypoxia in a Full-term Neonate.

A male infant is born at a community hospital at 37 weeks and 2 days of gestation via cesarean section because of failure to progress after induction of labor for oligohydramnios of unknown etiology. The maternal history is remarkable for 2 prior miscarriages. The pregnancy is complicated by advanced maternal age and low amniotic fluid index of 2.9. The mother had received prenatal care with unremarkable prenatal laboratory findings. The infant’s Apgar scores are 8 and 9, and he requires routine resuscitation. Ten minutes after birth, the infant is noted to be dusky in appearance with respiratory distress. Preductal pulse oximetry is notable for oxygen saturation of 60% to 65% in room air. After initiation of positive pressure ventilation, the oxygen saturation increases to 75% to 85%. The infant is given continuous positive pressure ventilation of 5 mm Hg at 100% fraction of inspired oxygen (Fio2), and his oxygen saturation increases to 90%. He is then transported to the NICU for further assessment, where chest radiography reveals a right-sided pneumothorax that is promptly treated with needle decompression, and he is then given 6 L of oxygen via high-flow nasal cannula (HFNC). The first arterial blood gas measurement approximately 1 hour after birth shows a pH of 7.13, partial pressure of oxygen (Po2) of 75 mm Hg (10 kPa), partial pressure of carbon dioxide (Pco2) of 55 mm Hg (7.3 kPa), bicarbonate of 24 …