Transcript for Saving a Life When Every Second Counts With CPR
roadside miracle. Did you see this harrowing photo everywhere today? The desperate woman on did side of the expressway performing cpr and breathing life back into her 5-month-old nephew. ABC's chief medical correspondent Richard Besser takes us behind those photos. Reporter: Pamela rauseo panicked. Driving in a traffic jam on a Miami highway, she had glanced over at her 5-month-old nephew, Sebastian, he was blue, not breathing. It was really the scariest moment of my life. Reporter: She pulled to the side, tried to dial 911, then jumped out on the highway. I had the baby in my arms, and he was completely limp, and I kept screaming for help and pointing to the baby. Reporter: Traffic stopped, people poured out of their cars to help, but Pamela wasn't waiting. Acting on instinct, she started cpr. She had taken a cpr course seven years ago. Within moments, she got baby Sebastian to breathe again. But what would you do? Most babies, like Sebastian, aren't having a heart attack. They're having a breathing problem. If you cover their nose and mouth with your own, like this, and puff some air in, they often start breathing on their own. If not, press on the middle of their tiny chest with just two of your fingers, stopping every 30 seconds to breathe. But the bottom line for babies, the most important thing, blow air into their mouths. It is likely to revive them. For adults, it's different. Since most likely it's their heart that's having the problem. So push hard, and fast, on their chest and keep it up. And here's a trick, push to the rhythm of "Stayin' alive" to keep them alive. As for baby Sebastian, the rescue squad took him to the hospital. I honestly -- I don't know how I remembered what to do. I just knew I couldn't let him die. I couldn't let him die. My sister trusted me with his life. Reporter: Today, Sebastian is awake, pink and being monitored in the hospital. The doctor is under very close medical observation but we anticipate he's going to be doing much better. So much admiration for her. How strongly do you breathe into the baby's nose and mouth? It's really important, when you're doing those breaths, out of the corner of your eye you want to look at the chest, if the chest is moving up then you're doing it right. Then you're pushing on the chest, you want to go down a good inch and a half. With two fingers. Two fingers. Get the pressure on the heart and the blood flowing. It's life-saving to know how to do this. Thank you so much, rich, tonight
This transcript has been automatically generated and may not be 100% accurate.