Panic attacks are incredibly common, and it can cause people to hyperventilate and to breathe out a lot, which breathes off the carbon dioxide, can make you feel very light-headed and means that you can just not be able to control your breathing at all. It is very, very frightening. It can give you palpitations, it can give you tremor. There's a lot of people get so frightened, that they think they're having a heart attack. If you suspect somebody is having a panic attack, please don't be tempted to use paper bags or anything that you may have heard about in the past.
The best way is to stay as calm as you can and breathe nice and calmly, too, and the calmer you are, the calmer they will be. Try and encourage them to breathe in and out very slowly. So, try and remove them from anything obvious that is causing them the distress, if you can, and try and get them to focus on breathing slowly in and out. Sometimes it can help to use your hands to do that. But breathing techniques have been shown to be the most effective to calm somebody when they're having a panic attack..
As found on YouTube