What is Emphysema?
The respiratory tract begins with the nose, nasal sinuses and mouth and continues as the throat, larynx, trachea, and left and right bronchi. The bronchi branch repeatedly till they form very small bronchioles called the terminal bronchioles. The terminal bronchioles lead to the alveoli or air sacs. The alveoli are elastic and springy sacs, comparable to a balloon. Exchange of oxygen and carbon dioxide takes place through the thin walls of the alveoli. The respiratory bronchioles and the alveolar ducts connect the terminal bronchioles to the alveoli and also take part in exchange of gases.
The alveoli get inflated when air enters them. Due to their elasticity, they spring back to their original size following expiration. In emphysema, due to the loss of their stretchiness, the lungs fail to empty air efficiently during expiration, and trap air. Consequently, they contain more air than normal leading to a state of hyperinflation.
Normally, the alveoli help in keeping the airways open allowing free exchange of air. In emphysema, the damaged alveoli are unable to keep the airways open either during inspiration or expiration, which collapse as a result. This is one of the reasons for airflow obstruction in emphysema.
The Global Initiative for Chronic Obstructive Lung Disease (GOLD) however no longer distinguishes between emphysema and chronic bronchitis in its definition of COPD.
Chronic obstructive pulmonary disease is a progressive condition, characterized by incomplete emptying of air from the lungs, and a resultant reduced airflow to the lungs. COPD encompasses chronic bronchitis, emphysema or a combination of the two.
Epidemiology of EmphysemaThe World Health Organization estimates that there were 3 million deaths caused by COPD in 2015 worldwide, which roughly translates to 5 percent of all deaths that year. Interestingly, more than 90 percent of deaths due to COPD occur in low and middle income countries, since strategies for disease control and prevention are either not effectively implemented or inaccessible in these parts of the world.
In the United States, as per the National Health Interview Survey from 2007, the prevalence of emphysema is 18 per 1000, and that of chronic bronchitis 34 per 1000. While the prevalence rate of emphysema has remained largely the same since 2000, that of chronic bronchitis has come down.
According to the Centers for Disease Control and Prevention, the number of deaths recorded due to emphysema is around 7455 people in 2014.
Around 3.4 million people (1.4%) in the United States are diagnosed with emphysema.People who generally smoke may have severe emphysema.
Gender wise, the prevalence of COPD was earlier higher in men, attributable mainly to increased rates of smoking among men. However with a rise in smoking among women in the last 30 years, the gap has been bridged. In fact, it is suggested that women may be more susceptible to development of emphysema as compared to men.
What are the Types of Emphysema?Depending on the part of the lungs affected, emphysema may be subdivided into
1. Centriacinar (centrilobular) type
2. Panacinar type
3. Paraseptal (Distal) type
- Centrilobular emphysema is the most commonly seen type of emphysema. It affects the respiratory bronchioles, mainly in the upper regions of the lung, while the alveoli are not affected. This type of emphysema is associated with cigarette smoking and exposure to dust.
- Panacinar emphysema involves the entire alveolus uniformly, and occurs predominantly in the lower regions of the lung. It is more commonly seen in persons with a genetic mutation called α1 antitrypsin deficiency with homozygous PiZZ α1 antitrypsin mutation. However, this form can also occur in smokers along with centrilobular emphysema.
- Distal emphysema preferentially involves the alveolar ducts and sacs. The regions around the lung septa (partitions in the lungs) and pleura (tissue covering the lung) are affected. Though air flow is not much restricted, the alveoli form large balloon-like structures called bullae. Large bullae may exert pressure and compress the surrounding lung tissue. The bullae in the upper part of the lungs can burst resulting in air in the chest, a condition called spontaneous pneumothorax.
What are the Causes of Emphysema?The major causes of emphysema include:
- Smoke - Tobacco smoke is the primary cause of COPD. Nearly 85 to 90 percent of COPD patients are past or current smokers. Passive smoking, where a person does not smoke but is exposed to cigarette smoke from the surrounding, also contributes to about 20 percent of cases. Women are more susceptible to the effects of cigarette smoke compared to men. Heavy exposure to marijuana smoke may also cause COPD.
- Air pollution - Both outdoor and indoor air pollution are associated with an increased prevalence of COPD. Persons living in large cities, or those exposed to exhaust fumes from vehicular traffic and industries are commonly affected. However, people in rural areas are also not spared. Poorly ventilated cooking fires using coal, cow dung or wood used in rural areas contribute to poor indoor air quality and can cause COPD. This form of cooking is seen in developing nations such as India, China and Sub-Saharan Africa, and affects mainly women. However, the contribution of air pollution to the development of COPD is minimal as compared to tobacco smoke.
- Occupational exposures - Exposure to dust, chemicals and fumes at place of work enhances the risk of COPD development. These contribute to around 10 to 20 percent of cases.
Industries and occupations involving high exposure include coal, cotton textile, welding and those involving chemicals such as cadmium and isocyanates predispose to the development of COPD. Exposure to silica dust may also contribute to COPD development.
- Genetic factors - The genetic condition α1-antitrypsin deficiency (α1-AT) is a known risk factor for emphysema. However, it has contributed to less than 5 percent of COPD cases. The role of other genetic factors is being investigated. The incidence of COPD is higher in relatives of COPD patients who are also smokers, in comparison to unrelated smokers, which suggests that other genetic factors may also play a role. Hereditary factors may also provide an explanation for the fact why some smokers never develop COPD, while non-smokers are diagnosed with this disease.
- Less well-defined factors - Poverty, asthma and hyperactive airways, low birth weight, and infections such as HIV/AIDS and tuberculosis may play a role in COPD development, though their role is not clear or well defined.
What are the Symptoms and Signs of Emphysema?COPD is a disease of slow progression, and symptoms usually become overt around 50 to 60 years of age. Patients with homozygous PiZZ α1-AT deficiency may present around a decade earlier. Symptoms and signs of emphysema include the following:
- Gradual onset of breathlessness on exertion
- Faster breathing with use of additional chest muscles
- Progressively worsening breathlessness, ultimately leading to shortness of breath at rest and inability to perform daily tasks and climbing stairs. Sudden exacerbations may require admission to a hospital
- Becoming easily tired and exhausted
- Reduced mental alertness
- Bluish discoloration of nails and lips (cyanosis) due to reduced oxygen content of the blood
- Change in the shape of the chest with an increase in the anteroposterior diameter, referred to as barrel chest
- On examination, the doctor may notice increased resonance on tapping the chest, and decreased breath sounds on both sides of the chest with prolonged expiration. Additional sounds like wheeze are likely to be present
- Patients with PiZZ α1-AT deficiency may experience liver dysfunction in childhood
How is Emphysema Diagnosed?History and physical examination - A diagnosis of emphysema may be suspected based on the history of gradually progressive breathlessness, especially in smokers or those who are exposed to dust and pollutants constantly. Physical examination of the chest may confirm the diagnosis of emphysema, which can be further strengthened by the following tests.
Spirometry is a test that is useful to diagnose COPD, assess response to treatment and determine the progression of the disease. Various parameters are assessed depending on the patients’ ability to breath into an instrument called a spirometer following specific instructions. Patients with COPD often have the following findings:
- Decrease in vital capacity - Vital capacity is the maximum volume of air that is breathed out after a deep inspiration
- Reduced FEV1/FVC ratio -FEV1 is the amount of air expired in one second of forced expiration, while FVC is the amount of air breathed out following a maximal expiratory effort. In COPD, the FEV1 and therefore FEV1/FVC ratio is reduced due to airflow obstruction during expiration The FEV1/FVC ratio is also referred to as Tiffeneau-Pinelli index that is used to diagnose the obstructive and restrictive lung disease.
- Forced expiratory time - A forced expiratory time is the time taken to breathe out. A forced expiratory time of more than 6 seconds is diagnostic of COPD.
Blood tests -
- Arterial blood gas analysis – The blood oxygen levels should be evaluated at sleep, at rest, during movement, and during exertion. In the initial stages of the disease, the oxygen saturation of the blood may be reduced moderately (hypoxemia), with no evidence of increased carbon-di-oxide (hypercapnia). In the advanced stages, there is marked hypoxemia with development of hypercapnia.
- Hematocrit – Hematocrit refers to the percentage of red blood cells in the blood. Reduced blood oxygen levels stimulate the body to produce more red blood cells, resulting in a condition called polycythemia. A hematocrit of more than 52 percent in men and higher than 47 percent in women is indicative of COPD.
- Serum bicarbonate levels – In COPD, serum bicarbonate levels increase. In the absence of arterial blood gas measurements, estimation of serum bicarbonate levels may be performed to assess disease progression.
- Serum α1-AT levels –The α1-AT levels may be measured if α1-AT deficiency is suspected. The normal level of α1-AT is 11 mmol/L and above. A diagnosis of severe deficiency is confirmed by values between 3 and 7 mmol/L. Genetic testing should be done for patients with values between 7-11mmol/L.
How is Emphysema Treated?Emphysema cannot be cured. Treatment is used to control the symptoms, retard the progression of disease, improve the quality of life and prolong survival. The following modalities of treatment are followed:
- General measures
- Supportive therapy
General measures include:
- Quit smoking - This might perhaps be the single most important intervention that would retard disease progression. Patients should be provided adequate support to help them to stop smoking. Second hand smoke exposure must also be avoided.
- Avoiding exposure to irritants - Exposure to respiratory irritants like air pollutants, burning incense and candles and automobile exhaust fumes that could exacerbate COPD should be avoided.
- Regular exercise - Regular exercise helps improve total lung capacity and should be encouraged.
- Avoiding exposure to cold draughts - Protection from cold is essential in COPD, since cold air will constrict the air passages and exacerbate the already existing obstructive symptoms.
- During cold weather, it is advisable to wear a scarf or even wear a cold air mask to cover the nose and mouth, to heat the air entering the lungs.
- Prevention of respiratory infections - People with emphysema should avoid respiratory infections. Getting the annual flu vaccinations and pneumococcal vaccinations as advised by the doctor, and staying away from people with cold or flu can help to prevent respiratory infections. Wearing a protective mask when moving in crowds, especially in the cold weather, and carrying a hand sanitizer while traveling may be additional measures to prevent infections.
Medications are used to control the symptoms of the disease. Some of the commonly used drugs include:
- Inhaled steroids - Steroids inhaled in the form of aerosols can relieve breathlessness. They may include corticosteroids like beclomethasone, fluticasone, budesonide and formoterol. Prolonged steroid use is associated with a risk of developing diabetes, hypertension (raised blood pressure), cataracts, weak bones and stomach ulcers.
- Bronchodilators - These drugs relieve breathlessness caused by narrowing and obstruction of air passages by relaxing the smooth muscle of the airways (bronchi). Examples of bronchodilators include a combination of ipratropium with salbutamol However, they don’t seem as effective in the treatment of emphysema as compared to their efficacy in asthma or chronic bronchitis.
- Antibiotics - Antibiotics are necessary when patients with emphysema develop a bacterial infection with symptoms of fever and productive cough.
Supportive measures improve the person’s general condition and improve oxygenation of the lungs.
- Diet and nutrition - A balanced and healthy diet is essential for optimal health. In the early stages of the disease, many patients are advised weight loss measures, whilst in the later stages, patients are often emaciated and need to put on weight.
- Supplemental oxygen - In emphysema, the oxygen levels in the blood are often low, and many patients benefit by supplemental oxygen administered via a tube that fits into the nostrils. Some patients in the advanced stages need 24 hour oxygen supplementation.
- Pulmonary rehabilitation - This involves learning breathing exercises and techniques to improve lung capacity, decrease breathlessness and develop better tolerance to exercise or even daily activities.
Different types of surgery are offered to patients to give symptomatic relief and restore lung function.
- Lung Volume Reduction Surgery – In this procedure, wedges of damaged lung tissue are removed. This will enable the remaining normal lung tissue to expand and work more efficiently, and eases breathing.
- Bullectomy – Removal of giant bullae that occupy a large part of the chest, compress the adjacent lung and lead to a decrease in FEV1 to less than 50 percent of expected value, may result in expansion of the surrounding normal lung and improve lung function.
- Lung transplant – A lung transplant indicated when patients fail to improve with all other treatment modalities.