Why does the reporter have a tube up his nose? why does the reporter have a tube up his nose? to replace the salts and other ions lost during the test to recycle the water he loses during the test to accurately measure core temperature as a feeding tube to replace lost nutrients?

The correct answer is to accurately measure core temperature.
The tube seen entering the reporter's nose is a thermistor which is used to measure the core temperature of the body with very high levels of accuracy. The tube reaches the esophagus, which is one of the most preferred locations for measuring the core temperature.
The core body temperature is the operating temperature of the human body and it refers to the temperature of the deeper structures of the body instead of the peripheral tissues. 
The esophagus is close to the left ventricle of the heart, it has a deep body location and a quick response to any changes in the body temperature.