Introduction to Emphysema

Introduction to emphysema

The lungs are a pair of organs in the chest that are primarily responsible for the exchange of oxygen and carbon dioxide between the air we breathe and the blood.

The lung is composed of clusters of small air sacs (alveoli) divided by thin, elastic walls or membranes. Capillaries, the tiniest of blood vessels, run within these walls between the alveoli and allow blood and air to come near each other. The distance between the air in the lungs and the blood in the capillaries is very small, and allows molecules of oxygen and carbon dioxide to transfer across the membranes.

Air reaches the alveoli via the bronchial tree. The trachea splits into the right and left mainstem bronchi, which branch further into bronchioles and finally ends in the alveolar air sacs.

When we breathe in, air enters the lung and the alveoli expand. Oxygen is transferred onto hemoglobin molecules in the red blood cells to be transported to the rest of the body for use. As oxygen attaches to the red blood cell, carbon dioxide, the waste product of metabolism, detaches and crosses into the alveoli to be exhaled. When we breathe out, the alveoli get squeezed by the elasticity in their walls and air is pushed out of the lungs.




What is emphysema?

Emphysema is a long-term, progressive disease of the lung(s) and occurs when the alveolar walls are destroyed along with the capillary blood vessels that run within them. This lessens the total area within the lung where blood and air can come together, limiting the potential for oxygen and carbon dioxide transfer.

In early emphysema, there is associated inflammation of the small airways or bronchioles that limits the amount of air that can flow to the alveoli. In more severe emphysema, there is also loss of elasticity in the alveolar walls that have not been destroyed. When the patient breathes out, the alveoli and small airways collapse. This makes it hard for air to get out of the lungs and makes it even harder for new air to enter.

As more of the lung is destroyed and the lung cannot maintain oxygen concentrations in the bloodstream, the body compensates by gradually increasing the breathing rate. After a while, even hyperventilation (hyper=more + ventilation=breathing) cannot maintain adequate oxygen levels, and the arteries in the lung begin to constrict or narrow. The heart has to work harder to push blood into these narrower blood vessels, causing the blood pressure in the lung arteries to increase (pulmonary hypertension). Over time, the extra work requirement causes the heart muscle to enlarge (hypertrophy) and can cause heart failure.