A 6-year-old boy is brought to the emergency room with a 3-hour history of fever of 39.5℃ and sore throat. The child appears irritability，sweating，and cyanosis with inspiratory stridor，reduced lung sound and tachycardiac. What should you do immediately?
A: Examine the throat and obtain a culture
B: Obtain an arterial blood gas sample and start an IV line
C: Order a chest x-ray and lateral view of the neck