A 70-year-old man presents with a severe nosebleed. His medical history includes COPD, depression, and a hemorrhagic stroke 3 years ago. His BP is 190/110 mm Hg, his pulse is 100 beats/min, and his respirations are 24 breaths/min. His medications include albuterol, sertraline (Zoloft), and multivitamins. Which of the following is MOST likely causing his nosebleed today?