When we breathe just into our chest—and we breathe about 18 times a minute, which is on the upper end of average, but so many people breathe this way—we only use 50% of that oxygen we take in ... Just a little bit of it actually makes it to the lungs and participates in gas exchange. But when we breathe slowly at a rate of about 6 times a minute, we use 85% of our breath—so a 35% increase in efficiency.