This app was mentioned in 3 comments, with an average of 3.33 upvotes
I don't mean to steal this guy's thunder, but I made a breathing app with a similar core concept (but with less features) that's available for android: https://play.google.com/store/apps/details?id=com.moodtools.breatheeasy
(less features, different animation, but same basic concept).
Hello, I'm not a nurse, and not a doctor, but I used to be a competitive swimmer/lifeguard/swimming instructor. When swimming, you HAVE to learn about proper breath control and listening to your body, or you can put yourself in real danger; so I got good at it, and learned as much as I could from coaches and doctors.
Here's my take: You aren't going to kill yourself doing this in a normal scenario. You need to be exhaling longer than you are inhaling, because you will increase buildup of CO2 and oxygen in your blood, and hyperventilate. Worst cause scenario, you will pass out and your body will naturally adjust breathing and chemical levels in your blood and fix it. Passing out is not really great for you though. It's easy to hurt yourself if you don't realise your about to pass out, and hit your head or other parts on sharp/hard surfaces near you on the way down. The ONLY time I EVER recomend hyperventilating for ANYONE is if you are in a scenario where you're going to have to hold your breath for a long time, and even then, a couple quick breaths is enough. I've had to do it to search for a missing person in murky water, or I've also seen navy SEALs use it to be able to swim 50+ yards underwater while practicing in their spare time. If you are doing this on purpose under "normal" circumstances where it's not physically necessary for your safety, please don't! It's not very good for you under normal circumstances! Regardless, I recommend you try an app to help with breath control. Use it for like... 3 minutes or however long you feel you need to, to get in a good rhythm. I use this one when I'm struggling with anxiety attacks: https://play.google.com/store/apps/details?id=com.moodtools.breatheeasy
The simplest stress relief app! Just breathe in and out as the circle grows and shrinks. More effective than it sounds!
Features: Customize timing, shape, colors, background, etc.
I just released it last week. Let me know if it works for you the next time you're feeling stressed! (Or if it doesn't work) Also, looking for beta testers for a gratitude journal app (PM me or reply to this comment for an invite)!