Pursed-lip breathing is particularly beneficial if you have COPD. COPD causes your airways to collapse. By prolonging the exhaling portion of breathing, pursed-lip breathing creates a little bit of back pressure, called positive end expiratory pressure (PEEP). This pressure helps keep the airways open so that carbon dioxide that's trapped in the lungs can get out.
One study of pursed-lip breathing in people with COPD found that it reduced dynamic hyperinflation. Dynamic hyperinflation occurs when you start to inhale before you've finished exhaling from your last breath. When this happens, you still have air in your lungs from your last breath, so it reduces how much air you can breathe in.
The study also showed that pursed-lip breathing helped improve exercise tolerance in people with COPD. It also improved their breathing pattern and increased the amount of oxygen in their blood.
Pursed-lip breathing also gives you a sense of control over your breathing. This can help prevent the cycle that starts when you have trouble breathing and then become anxious.