A nurse is teaching a client with emphysema how to perform pursed-lip breathing. The client asks the e to explain the purpose of this breathing technique. Which explanation should the nurse provide?

Pursed-lip breathing is a technique in which the client inhales slowly through the nose and exhales slowly through partially closed (pursed) lips, as if blowing out a candle. In clients with emphysema, the alveoli lose their elasticity, and the small airways tend to collapse during exhalation, trapping air and leading to hyperinflation. Pursed-lip breathing creates a mild back-pressure in the airways during exhalation, which helps keep small airways open longer, thereby prolonging the expiratory phase and allowing more complete emptying of the lungs. This improves gas exchange by reducing air trapping, decreasing the residual volume, and improving ventilation. Option A correctly identifies that the technique prolongs expiratory time, improving lung function, which is the primary physiological benefit. Option B is incorrect because pursed-lip breathing does not increase inspiratory muscle strength; inspiratory muscle training is a separate exercise. Option C — decreasing use of accessory breathing muscles — is a secondary benefit and consequence of improved breathing efficiency, not the primary purpose of the technique. Option D is incorrect because pursed-lip breathing specifically prolongs the expiratory phase, not the inspiratory phase. Students often confuse inspiration and expiration in this context, so remembering that emphysema impairs exhalation due to air trapping helps anchor the correct answer.