Final answer:
Transcutaneous PCO2 is the noninvasive device used for monitoring carbon dioxide tension in a premature newborn, being safe and suitable for delicate health conditions.
Step-by-step explanation:
The noninvasive monitoring device suitable for a premature newborn to monitor carbon dioxide tension is transcutaneous PCO2. This method involves measuring the partial pressure of carbon dioxide through the skin, which is a safe and noninvasive procedure especially suitable for newborns or infants with fragile health conditions. Capnography, although used for measuring CO2, is typically a part of anesthesia machinery or for patients who aren't critically ill and therefore, not the safest option for a premature newborn. Point of care PCO2 and in vivo PCO2 measurements are usually more invasive as they often involve direct sampling of blood, which might not be the ideal first choice for such delicate patients.