Pursed-lip breathing is a technique that allows the control of oxygenation and ventilation. The technique requires a person to inspire through the nose and exhale through the mouth at a slow controlled flow. The expiratory phase of respiration is going to prolong when compared to inspiration to expiration ratio in normal breathing. This technique creates a back pressure producing a small amount of positive end-expiratory pressure (PEEP).
The positive pressure created opposes the forces exerted on the airways from the flow of exhalation. As a result, pursed-lip breathing helps support breathing by the opening of the airways during exhalation and increasing excretion of volatile acids in the form of carbon dioxide preventing or relieving hypercapnia. Through purse-lip breathing, people can have relief of shortness of breath, decrease the work of breathing, and improve gas exchange. They also regain a sense of control over their breathing while simultaneously increasing their relaxation.
For Pursed-lip breathing (PLB) to be effective, the individual must be able to perform the technique correctly. The technique requires proper coordination to maintain prolonged exhalation. As for the therapeutic effects, they are short-lived. The technique is limited to 3 to 5 breaths since prolonging the duration of the technique causes fatigue of the respiratory muscles and significantly lower than normal levels of carbon dioxide in a normal individual potentially leading to a decrease perfusion pressure in the brain causing syncope. Without the proper use of purse-lip breathing, an individual could exacerbate air trapping and carbon dioxide retention.