Emphysema vs Chronic Bronchitis

Introduction

Emphysema is a type of Chronic Obstructive Pulmonary Disease (COPD) that progressively affects the lungs. It is mainly characterised by airway and alveolar damage, which lead to respiratory symptoms such as a persistent cough. In the case of emphysema, the air sacs (also known as alveoli) in the lungs are damaged. With age, the inner walls of the alveoli get weaker and break. This causes an increase in air space. In fact, the many small air spaces found in a healthy individual are replaced by large air spaces. The lungs’ surface area is therefore reduced along with the levels of oxygen reaching the blood. In addition, the compromised alveoli cause the “old” and oxygen-depleted air to remain trapped, which explains the characteristic shortness of breath found in emphysema. 

Chronic bronchitis also belongs to the COPD category. It is generally characterised by an inflammation of the bronchial tubes, which carry air to the lungs. This condition also causes shortness of breath and a persistent cough. While being two different diagnoses and entities, chronic bronchitis and emphysema share similar features. In fact, the majority of patients diagnosed with emphysema also suffer from chronic bronchitis. 

What is Emphysema?

Causes and Risk Factors

There are several causes of emphysema, the main one being long-term exposure to airborne irritants and noxious gases. In fact, smoking tobacco and/or marijuana has been found to cause emphysema. In addition, air pollution, dust and chemical fumes are also causative agents of emphysema. While there are several factors that come into play, smoking remains the main cause of emphysema, and more generally, COPD. In fact, 80 to 90% of people with COPD are smokers. In addition to smoking, environmental pollutants such as sulphur dioxide heavily impact the development of emphysema, especially in developing countries. Genetics also play a small part in this condition as there is a rare type of emphysema that is caused by an inherited protein deficiency. Alpha-1-antitrypsin is a protein responsible for maintaining the elastic structure of the lungs. A deficiency in this protein can lead to emphysema. However, this genetic mutation is only responsible for 1 to 2% of emphysema cases. 

Symptoms (For each type)

The symptoms of emphysema are caused by damage to the lungs. In fact, there is an abnormal and permanent dilatation of airspaces in the alveoli. This is due to the action of the proteinases, enzymes that are responsible for damaging and destroying the elastin fibre in the lungs. The damage inflicted on the lungs results in a decrease in the capillary and alveolar surface area, which in turn leads to a decrease in gas exchange. In other words, there is less oxygen being delivered into the bloodstream and the rest of the body. The different parts of the airways that can be damaged are the respiratory bronchiole, the alveolar sacs, the alveolar ducts and the alveoli. Collectively, they are referred to as the acinus. The different subtypes of emphysema are defined based on which part of the acinus is affected. 

  • First, there is centrilobular emphysema, which is the most common type and is generally associated with smoking. This condition is also very common in coal workers, as they are heavily exposed to large quantities of pollutants. 
  • Second, there is the genetic subtype of emphysema, panacinar emphysema. This condition is mainly seen with Alpha-1-antitrypsin deficiency. 
  • Finally, there is paraseptal emphysema. This condition can occur by itself or in association with the other two subtypes. If it occurs alone, it is usually associated with spontaneous pneumothorax in young adults. 

The three subtypes present more or less of the same symptoms. In fact, in all cases, inflammatory cells such as macrophages, T lymphocytes and neutrophils are activated, and they release several different proteinases that lead to mucus hypersecretion. This in turn contributes to the development of emphysema symptoms. In addition, due to the proteases secreted by the inflammatory cells, elastin, a component that is crucial for maintaining the integrity of the lungs’ small airways, is heavily affected. This leads to an increased susceptibility to lung destruction and airspace enlargement. 

Smoking increases the secretion of mucus and the release of neutrophilic proteolytic enzymes that severely damage the acinus. It also inhibits the activity of anti-proteolytic enzymes which could help reduce the damage to the lungs. 

Diagnosis

Usually, patients have very non-specific symptoms such as shortness of breath and a persistent cough without any sputum. However, as time goes on and the disease progresses, the cough and shortness of breath get progressively worse. In fact, shortness of breath becomes significantly worse when doing any physical activity and even when resting. In addition, due to the obstruction of airflow, wheezing can also become worse. With the progression of this condition, if it is not treated, the individual can lose a lot of weight due to the constant inflammation and the energy spent on breathing. The more the airways get damaged, the more severe the symptoms become. This damage in the lungs leads to increased shortness of breath and a severe cough that may be accompanied by sputum due to an acquired infection. 

It is important to consult a physician if you are experiencing recurrent and persistent symptoms of emphysema, or COPD more generally. During a physical exam, the patients usually look like they have lost weight and muscle mass, but they do not show a blue/purple discolouration due to deoxygenation. In order to properly diagnose emphysema, Pulmonary Function Testing (PFT) is done. This is done in the form of a ratio, FEV/FVC, to diagnose obstructive and restrictive lung diseases. There are four stages of emphysema. A mild stage has an FEV greater or equal to 80%. A moderate stage has an FEV1 less than 80% predicted. A severe stage has an FEV1 less than 50% predicted. Finally, a very severe stage has an FEV1 less than 30% predicted. The lung volume measured indicates the amount of air trapped. The ability to get rid of carbon monoxide is decreased because of the damaged airways. In case of severe emphysema, a chest x-ray may be helpful as healthcare professionals would be able to visualise the damaged alveoli. 

Treatments

Unfortunately, there is no treatment for emphysema. However, managing the risks by getting tested for the mutation, avoiding smoking, and by living in a relatively clean atmosphere can slow the progression of the disease. Bronchodilators and anti-inflammatory drugs can be used to alleviate the symptoms. Supportive therapy such as oxygen therapy and ventilatory support can also be used to manage the symptoms.

What is Chronic Bronchitis?

Causes and Risk Factors

As previously stated, chronic bronchitis is long-term inflammation of the bronchi. It is most common in smokers and is categorised as COPD along with emphysema. Bronchitis usually occurs in the case of an infection. In fact, in the case of inflammation, the body produces more mucus which leads to an increased cough. Bronchitis is considered chronic if an individual has a recurrent cough and mucus that lasts for three months or at least two years in a row. Other diseases such as tuberculosis also need to be ruled out first. The main cause of chronic bronchitis is smoking, including both direct and second-hand smoking. Although other factors such as infections play a role in the development of bronchitis, smoking remains the main cause and risk factor for this condition. In fact, if you are diagnosed with chronic bronchitis, it is important to stop smoking as soon as possible to avoid worsening the symptoms. 

Symptoms

Some chronic bronchitis symptoms are very similar, even common, to emphysema symptoms. However, in the case of bronchitis, the cough is accompanied by mucus and flu-like symptoms such as a sore throat, body pain, headaches and a runny nose. In addition, chronic bronchitis patients, unlike emphysema patients, present with bluish discolouration of the lips, skin and fingernails due to deoxygenation. They can also have swollen feet, severe and frequent infections, along with heart problems. The symptoms shared between chronic bronchitis and emphysema are shortness of breath, a persistent cough (with sputum in the case of chronic bronchitis) and weight loss. 

Diagnosis

It is important to see a GP if the cough is persistent or gets progressively worse and you start coughing up mucus which could be clear, yellow/grey or green in colour. If the shortness of breath gets worse and is accompanied by a high temperature, or if you already have a lung condition such as asthma, then it is also important to consult your GP. 

To diagnose chronic bronchitis, the GP needs to rule out other possibilities. Some of the tests done to diagnose bronchitis are a chest X-ray, and an analysis of the mucus samples taken from you. An LFT may be ordered in some cases, however, a spirometer is usually used to measure the air volume in the lungs. A decreased lung capacity can be an indicator of a respiratory problem. 

It is important to remember that bronchitis can be caused by bacterial and/or viral infections. Whereas, emphysema is mainly caused by environmental factors. 

Treatments

Just like emphysema, there is no cure for chronic bronchitis. However, with appropriate management of the disease, the symptoms can be alleviated. For instance, a well-balanced diet along with regular and moderate physical activity can help ease the symptoms. However, the most important “treatment” is avoiding and quitting smoking. In addition, the use of inhalers can help open up the airways and thin the mucus, thus alleviating symptoms.

Summary

To sum up, emphysema and chronic bronchitis are two similar respiratory conditions that affect around 300 million individuals yearly. They are both parts of the COPD category. While these two conditions share many similarities, it is important to remember that chronic bronchitis is usually accompanied by sputum production and can be due to an infection. However, in both cases, smoking is the main cause and risk factor, which is why it is important to avoid smoking or even quit it altogether.

References

  1. Hopkinsmedicine.org. 2022. Chronic Bronchitis. [online] Available at: <https://www.hopkinsmedicine.org/health/conditions-and-diseases/chronic-bronchitis> [Accessed 30 May 2022].
  2. Mayo Clinic. 2022. Emphysema - Symptoms and causes. [online] Available at: <https://www.mayoclinic.org/diseases-conditions/emphysema/symptoms-causes/syc-20355555> [Accessed 30 May 2022].
  3. Mouronte-Roibás, C., Leiro-Fernández, V., Fernández-Villar, A., Botana-Rial, M., Ramos-Hernández, C. and Ruano-Ravina, A., 2016. COPD, emphysema and the onset of lung cancer. A systematic review. Cancer Letters, 382(2), pp.240-244.
  4. nhs.uk. 2022. Bronchitis. [online] Available at: <https://www.nhs.uk/conditions/bronchitis/> [Accessed 30 May 2022].
  5. PMC, E., 2022. Europe PMC. [online] Europepmc.org. Available at: <https://europepmc.org/article/NBK/nbk482217#free-full-text> [Accessed 30 May 2022].

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