You respond to a call in a residential neighborhood. Upon your arrival, you find a male who appears to be in his 50s lying in the grass next to a two-story house. He does not respond to your questions. You notice an extension ladder extended to the roofline and a toolbox on the roof. As you begin your initial assessment, you find the patient has noisy, shallow respirations at 8 breaths per minute and obvious bleeding from both legs. His pulse is 120 beats per minute and difficult to palpate at the radius. Your first priority in treating this patient is to