You have arrived at the scene of a call for a "man down." As you enter the residence you note that your patient is a male in his mid-60s who is awake but does not seem to acknowledge your presence. He is perspiring profusely, has cyanosis of his ears and lips, and has rapid, shallow respirations. Which of the following should you do first?

A) Obtain the patient's medical history.
B) Listen to his lung sounds.
C) Assist ventilations with a bag-valve mask and supplemental oxygen.
D) Check for a radial pulse.

C