Explain "Emphysema results in increased compliance of the lungs so that it does not generate enough recoil, making it difficult for the lungs to return to resting volume. Thus patients are unable to exhale normally, causing a buildup of CO 2 in blood. Patients with emphysema have trouble moving air mechanically. Patients become hypoxic during exercise, primarily due to the body not being able to handle the excess ventilatory demand from increase in CO 2 production."?