What is emphysema?
Emphysema is referred to as the destruction of the alveolar air sacs in the lungs and it belongs to a group of respiratory diseases called chronic obstructive pulmonary disease (COPD). In emphysema, there is a loss of elastic recoil and destruction of small airways which leads to air trapping in the lung. The hallmark of emphysema is its spongy appearance, and there are many types of emphysema. Usually, emphysema coexists with chronic bronchitis, which is inflammation of the airways in the lungs.
Causes of emphysema
- Imbalance of proteases and antiproteases
When we breathe in, most of the foreign particles are filtered out by the lungs, particularly by the mucus in the lungs, which allows the airways to keep the air in the distal parts of the lungs clean. But there are no defense mechanisms in the distal portions of the lung, except alveolar macrophages, which can eat foreign particles that accidentally go into the bottom of the lungs. When these macrophages eat the foreign particles, it causes a small amount of inflammation in the lower part of the lungs. It is common to have some level of inflammation in the alveolar air sacs. So there is a little constant inflammation in the lungs.
Macrophage-induced inflammation produces proteases as byproducts that can damage the alveolar sac walls, but the body (liver) produces proteins called antiproteases to protect against proteases, and the most important antiprotease is called Alpha-1 antitrypsin. Therefore, the protease damage of the air sac is balanced by the antiproteases. In emphysema, this balance is disrupted by either overproduction of the proteases or the decreased production of the antiproteases.
- Cigarette smoking
Smoking is the first common cause of emphysema. Emphysema coexists with chronic bronchitis because the major cause of both diseases is smoking. Smoking brings many foreign particles to the distal portion of the lung and induces macrophage inflammations and eventually leads to the overproduction of proteases, that can destroy the alveolar air sac. In this case, the protease damage overrides the antiprotease protection.
- Alpha-1 antitrypsin deficiency (A1AT)
Which is the most common antitrypsin in the blood. Therefore, deficiency of A1AT results in the inability to protect the alveolar air sac against protease damage. So eventually this can lead to emphysema.
Symptoms and signs of emphysema
Emphysema is usually asymptomatic until 50% of the development. Patients with emphysema have an increased risk of bronchitis, pneumonia, and other lung infections.
- Shortness of breath even at rest
This is the main symptom of emphysema. Initially, shortness of breath can be mistaken for other illnesses, but eventually, it becomes shortness of breath even at rest.
- Coughing without sputum (late-stage emphysema can induce sputum)
Because this is not chronic bronchitis
- Wheezing
- Prolonged expiration with pursed lips
- Weight loss
- Fatigue
- Enlarged AP diameter of the chest ( AKA barrel chest)
Loss of elastic recoil of the lungs due to rupture of the alveolar sac results in an enlarged diameter of the chest known as "barrel-chest", which is the hallmark finding of the emphysema
Risk factors of emphysema
- Smoking
- Exposure to secondhand smoke (This is the smoke that is inhaled by someone else's cigarette or tobacco)
- Dust
- Exposure to inhaled toxins (can lead to epithelial cell death and chronic inflammation)
- Inhaling biomass fuels
Types of emphysema
There are four types of emphysema but two of them are the most important such as centriacinar emphysema and panacinar emphysema.
The functional unit of the lung (acinus)
Centriacinar emphysema
The main cause of centriacinar emphysema is smoking. The functional and structural unit of the lung is known as "acinus". Generally, smoke and its other particles damage the central part of the acinus and eventually lead to emphysema which is known as centriacinar emphysema and it is more severe in the upper lobe of the lung.
Panacinar emphysema
referred to as the disruption of the entire acinus. The most common cause of panacinar emphysema is A1AT deficiency. Panacinar emphysema is more severe in the lower lobe of the lung. Patients who have A1AT deficiency may also develop liver cirrhosis. Because the Alpha-1 antitrypsin produced by the liver is misfolded due to mutations and eventually these misfolded proteins accumulate in the endoplasmic reticulum of the hepatocytes and eventually damage the liver cells, finally leading to liver cirrhosis.
Periacinar emphysema
Characterized as distal acinar emphysema, predominantly affecting the distal alveolar sacs and ducts. It's usually more severe in the upper half of the lungs. The cause is unknown and is more common in spontaneous pneumothorax in young adults.
Interstitial emphysema
Known as the accumulation of air in the interstitial tissues due to the traumatic rupture of an airway.
Complications of emphysema
Hypoxemia
Hypoxemia means a low level of oxygen in the blood, especially in the arteries (paO2 < 60) due to the destruction of capillaries that are present in the wall of air sacs. These patients are called "pink puffers".
Cor pulmonale
Hypoxemia will lead to constriction of blood vessels and eventually, the right heart pump against these constricted blood vessels and undergo hypertrophy. Finally, this will result in right heart failure, known as cor pulmonale.
Pneumothorax
A collapsed lung. It is a life-threatening complication of severe emphysema.
Bullae
Bullae represents large holes in the lung and has an increased risk of leading to pneumothorax
Treatments for emphysema
- Stopping smoking - This is the primary way to treat emphysema
- Anti-inflammatory medications - these medications can protect the air sac walls against protease-induced damage. However, long-term usage may lead to some side effects such as hypertension, high blood sugar, and osteoporosis.
- Bronchodilator medications - these medications are used to relax the muscles around the airway.
- Oxygen therapy - because emphysema patients can't get enough oxygen into the blood due to damage to air sacs. this treatment reduces the chance of developing cor pulmonale and hypoxemia.
- Surgery - is used to remove a damaged portion of the lung. this may reduce the pressure on the breathing muscles and can increase the lung elasticity
