Final answer:
A patient with emphysema has to use accessory muscles for forced expiration due to decreased lung elasticity and air trapping, which mimics the muscle engagement found in forced breathing.
Step-by-step explanation:
Emphysema is a chronic lung disease that leads to difficulties in exhaling air from the lungs, primarily because of the destruction of the alveolar walls which decreases the surface area for gas exchange and decreases the lungs' elastic recoil. This condition results in trapped air in the lungs at the end of exhalation. Therefore, the patient with emphysema must often rely on accessory muscles of respiration for forced expiration, as the natural elastic recoil of the lungs is insufficient. Accessory muscles such as the abdominal obliques force abdominal organs upward against the diaphragm, and internal intercostals help to compress the rib cage to reduce thoracic cavity volume and aid in exhalation.
Unlike normal breathing, which can rely on the passive recoil of the lungs to exhale, patients with emphysema use a method similar to forced breathing, engaging multiple muscle groups to expel air actively from the lungs due to decreased lung compliance and elasticity.