In 2014, Meuret and a team of researchers gathered 120 randomly selected asthma sufferers, measured their pulmonary lung functions, lung size, and blood gases, and then gave them a handheld capnometer, which tracked the carbon dioxide in their exhaled breath. Over four weeks, the asthmatics would carry the device around and practice breathing less to keep their carbon dioxide levels at a healthy level of 5.5 percent. If the levels dipped, the patients would breathe less until the carbon dioxide levels rose back.
