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Monday, February 8, 2016

What is Emphysema?

The following was originally published by me at on on September 2, 2015

Essentially, emphysema starts in the lung parenchyma, which consists of the small bronchi, alveoli, and capillaries. For a quick review of pulmonary anatomy, see take my journey down the respiratory tract.

Alveoli. These are small balloon-like structures that inflate like balloons when you inhale. After full inhalation, elastic recoil allows them to resume their natural shape, allowing exhalation to occur. They join with capillaries, so it’s here gas exchange occurs.

Emphysema. Certain conditions -- like smoking -- cause alveolar walls to become inflamed and breakdown.  They lose their elasticity, or their ability to regain their normal shape after a full inhalation. They eventually rupture, creating small air spaces. This also destroys surrounding capillaries, creating alveoli that no longer participate in gas exchange.  So emphysema is the gradual, progressive loss of lung tissue.  

Barrel Chest.  Lacking elastic tissue, alveoli lose the ability to contract during exhalation.  When the elastic tissue of enough alveoli are destroyed, these portions of the lungs expand all the way to the ribcage.  This gives the appearance of having a chest full of air even after fully exhaling.

Airflow Limitation.  When lungs are fully expanded this way, pressure is put on small bronchi causing them to become narrow.  This causes increased resistance to air flowing through airways during both inspiration and expiration, slowing the flow of air. This is airway obstruction that does not respond to rescue medicine.

Prolonged Expiration.  During exhalation, pressure inside the chest increases, thereby squeezing the airways, causing even more resistance to airflow.  This causes a prolonged exhalation.  Expiratory airflow may be so limited that you cannot blow out a candle.

Air Trapping.  The inability to exhale completely causes air to become trapped inside your lungs.  In other words, air can more easily get in than out. This may also add to the appearance of a barrel chest.

Bulla (Bullae).  As more lung tissue is destroyed over time, this creates one large air space rather than many smaller ones. These air spaces are called air pockets, blebs, or bullae, and range in size from 1-20 cm across. When representing greater than 30 percent of a hemithorax (half of the chest) they are considered giant bullae. They are diagnosed either by chest X-ray or CT.

Bullous Emphysema.  Bullae were first reported in 1937 by Burke in a 35-year-old man who had progressively worsening shortness of breath. He referred to it as Vanishing Lung Disease because the lungs appeared to be disappearing on X-ray. While bullae may occur spontaneously in young men, they may also be associated with emphysema.

Symptoms. Even giant bullae may present with no symptoms. However, as bullae expand they may take up too much space and compress surrounding lung tissue, inhibiting otherwise functional airways from distributing air. This may result in progressively worsening shortness of breath, chest pain, and low oxygen levels.

Complications.  Bullae may become infected and cause an abscess to form that may leak out into the pleural cavity causing empyema, a painful infection that may cause worsening shortness of breath. Bullae may rupture or pop, allowing inhaled air to escape into the pleural cavity that surrounds the lungs. This causes respiratory distress, sharp chest pain, and anxiety.  

Treatment. Generally, this is no different than for typical emphysema, and includes:
Bullectomy. This is when the bullae is surgically removed, allowing surrounding alveoli to re-expand, once again become functioning gas exchange units. Surgery will not cure the emphysema, but has been shown to greatly reduce symptoms and improve quality of life, if you qualify.

What to do. American Thoracic Society COPD Guidelines suggest that most people with COPD have enough good alveoli that they do not need surgery, or have too many smaller bullae to benefit from surgery. So the most logical choice for most patients with bullous emphysema is to continue working with your doctor to maintain good control of your COPD.

Further reading and References:
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