Opening the airway is usually done by using the head-tilt, chin-lift method. The intent is to pull the tongue off the back of the throat and let air pass unobstructed. Sometimes it's very hard to get the airway open this way, even when paramedics or EMTs are doing it. So, if air doesn't go in on the first try, tilt the head down and back up again, then try another rescue breath.
Whether it works the second time or not, start pushing on the chest. It's important to get blood moving around the body. There's probably still plenty of oxygen in the bloodstream and only by pushing on the chest will that blood get to the brain and the heart.
In years past, all the focus on delivering those rescue breaths no matter what meant some victims didn't get chest compressions as quickly as they should. The assumption used to be that if air didn't go in, there must be something stuck in the airway that needed to come out before anything else was done.
Now we recognize how difficult it is to open the airway. It doesn't mean there's a chunk of steak in the airway just because the chest doesn't rise. Indeed, in some cases of cardiac arrest, rescuers are encouraged to skip the rescue breathing entirely and provide hands-only CPR.
Only 2 breaths are necessary, whether successful or not. If they both work, great. Start chest compressions. If the first one works and the second one doesn't, start chest compressions. If both of them fail, start compressions. Regardless what happens after a second breath (or a second try), start chest compressions.
So here are the important steps (assuming you've already called 911 or you're having someone else do it):
- Head-tilt, chin-lift and try a breath.
- Try it again.
- Push on the chest 30 times.