# Emphysema --- **Emphysema** is a disease that is a part of [[COPD]] where there is irreversible damage to the [[lungs]] that reduces the amount of surface area available for [[tissue gas exchange]]. It is caused by [[inflammation]] of the air passages distal to the terminal bronchioles as well as a destruction of the pulmonary elastic connective tissue. In response to these conditions, the individual [[alveoli]] enlarge and merge together, which both decreases the number of individual alveoli, drastically reduces the total surface area of the lungs. These enlarged, inelastic alveoli trap dead air in the lungs, making them chronically inflated, which effectively reduces the lung capacity. Patients with emphysema must actively work to [[pulmonary ventilation|exhale]] because it doesn't happen on its own, and this actually takes a *lot* of energy. They need to have hugely increased amount of calories to fuel the active expiration. This is also how [[barrel chest]] can develop. A structure called a **bleb** can form on the edge of the lung with the blistered alveoli. If enough blebs occur together it's called a **bullae**. ![[emphysema.png]] ## Risk Factors Emphysema can be caused by a [[genetic disorder]], where individuals lack a working gene that produces a protein that prevents the body's [[neutrophils]] from accidentally damaging the alveoli. However, most cases of emphysema are caused by [[smoking]], which damages the tissues of the lungs. Once damaged, the tissue cannot regenerate. ## Signs & Symptoms - cachexia (wasting) - loss of muscle mass due to all the energy they burn trying to exhale - The damaged alveoli (called "bullae") can rupture and leak air, causing a [[pneumothorax]]. ## Emphysema & High O2 Since people with emphysema can't expiated fully then CO2 levels (and hence H+ levels) stay high. Chemoreceptors give up because no one is listening to them. As a result, doctors give them low [[oxygen therapy|oxygen saturation goals]] that will trigger the [[pulmonary ventilation#Breathing Regulation|peripheral chemoreceptors]]. Central chemoreceptors pick up extra CO2 (which can be translated to H+ ions). What do they do when they pick up that information? The information is sent to the respiratory center, which sends information down the **phrenic** nerve to the **choroid plexus** to innervate the diaphragm, to increase the respiration rates. Peripheral chemoreceptors, also do deal with CO2 and H+, but **also** deal with *low O2 levels*. And then they send *that* information to the respiratory centers and so forth. ___