Chest pains are very serious business. Any time anybody tells you they have pressure in their chest, they feel like their chest is squeezing, they have any kind of pain, especially if it's radiating down their arm, you want to call 911 immediately. It doesn't matter how old you are. It doesn't matter what kind of life style you are. You can think you are the healthiest person in the world. You want to get help immediately.
Why you're waiting for the ambulance to arrive, you want to lay the person down, keep them comfortable. Even sit down, they don't have to be laying down. But sit down or lay down. If you have baby aspirin available, you can have them chew two of those. If they have a history of angina or heart attacks, they may have nitroglycerin with them. If they have that, go ahead and tell them to take one of their pills and put it underneath their tongue. If you suspect a GI problem, if you suspect a heart murmur, you can try antacid, but call 911 immediately. Get help immediately. Things can go from bad to worse very quickly and you want help as soon as you can.
If the person stops breathing or the person looses their pulse, you're going to want to start CPR. A lot of people are going to want to write off their chest pain as something minor, something they can take care of, something they can muscle through on their own. You might think, oh, it's just heartburn. Hopefully it is. Hopefully it's something very minor. But if it isn't, you're going to want to have help with you quickly because it can go from bad to worse very fast.