Final answer:
The RT should use a heated high-flow nasal cannula for a premature infant requiring supplemental oxygen at 30% to prevent cold stress and provide precise oxygen levels.
Step-by-step explanation:
To prevent cold stress and deliver a precise oxygen concentration to a newborn infant born at 30 weeks gestation requiring supplemental oxygen at 30%, the respiratory therapist (RT) should select a heated high-flow nasal cannula. This device is particularly suited for premature infants as it can provide both the required warmth to maintain the infant's body temperature and the accurate oxygen levels needed without the risks associated with more invasive forms of respiratory support. The heated high-flow nasal cannula minimizes cold stress by warming and humidifying the air, which is vital for the well-being of premature infants, who are at a high risk for cold stress due to their underdeveloped bodies and regulatory systems.