Final answer:
To begin positive-pressure ventilation, a carefully titrated supplemental oxygen concentration is used for a newborn at 34 weeks' gestation to maintain oxygen saturation between 91% and 95%, as immature lungs are susceptible to damage from too much oxygen.
Step-by-step explanation:
A newborn of 34 weeks' gestation who is apneic at birth and requires positive-pressure ventilation should be started on a supplemental oxygen concentration that is carefully titrated to achieve adequate oxygenation without causing oxygen toxicity. Preterm infants have immature lungs, and providing too much oxygen can damage the delicate lung tissue and lead to complications, such as retinopathy of prematurity. Proper lung development oftentimes is not achieved until early childhood, which makes it essential to use ventilators, application of CPAP, administration of pulmonary surfactant, and sometimes supplemental oxygen to support the premature infant.
The exact concentration of oxygen to be used depends on the clinical protocol and the infant's response, with the aim of maintaining adequate but not excessive oxygen saturation levels, usually between 91% and 95% in preterm infants. Since the respiratory system is not fully mature until early childhood, infants born as early as 28 weeks gestation can breathe on their own due to the maturity of enough alveoli, but may still require assistance to ensure sufficient oxygenation and avoid respiratory distress.