An old fellow is driving home. It's late at night. He's travelling along the highway, and he's some considerable distance from home. Suddenly, he feels himself having a heart attack. He says, "Oh my God. It's the big one." Thinking quickly, he takes the first available exit.

As luck would have it, he winds up in a residential neighborhood. It's very late at night. He pulls over to the side of the road behind some parked cars. He's fading fast, but he has the presence of mind to pull out his cell phone and call 911.

He says to the dispatcher, "I need help. I'm having a heart attack." She says, "Where are you?"

And the rest of the conversation goes something like this:
He: "I don't know where I am."
She: "What exit did you take?"
He: "I don't remember."
She: "Were you going north or south or east?"
He: "I don't remember."
She: "Can you tell me what street you're on?"
He: "I'm in the middle of the block. I'm parked behind some cars. I didn't see any street signs."
She: "Start blowing the horn. Someone will come out of the house."

No one comes out.

She then asks him to do one more thing. Minutes later, an ambulance is on its way there and saves his life.

What did she ask him to do?