Definition of COPD
Chronic obstructive pulmonary disease (COPD), also known as chronic obstructive lung disease (COLD), chronic obstructive airway disease (COAD), chronic airflow limitation (CAL) and chronic obstructive respiratory disease (CORD), is the occurrence of chronic bronchitisor emphysema, a pair of commonly co-existing diseases of the lungs in which the airways narrow over time. This limits airflow to and from the lungs, causing shortness of breath (dyspnea). In clinical practice, COPD is defined by its characteristically low airflow on lung function tests. In contrast to asthma, this limitation is poorly reversible and usually gets increasingly worse over time.
COPD is caused by noxious particles or gas, most commonly from tobacco smoking, which triggers an abnormal inflammatory response in the lung.
The diagnosis of COPD requires lung function tests. Important management strategies are smoking cessation, vaccinations, rehabilitation, and drug therapy (often using inhalers). Some patients go on to require long-term oxygen therapy or lung transplantation.
The twofold nature of the pathology has been studied in the past. Furthermore, in recent studies, many authors found that each patient could be classified as presenting a predominantly bronchial or emphysematous phenotype by simply analyzing clinical, functional, and radiological findings or studying interesting biomarkers.
Chronic bronchitis is defined in clinical terms as a cough with sputum production on most days for 3 months of a year, for 2 consecutive years. In the airways of the lung, the hallmark of chronic bronchitis is an increased number (hyperplasia) and increased size (hypertrophy) of the goblet cells and mucous glands of the airway. As a result, there is more mucus than usual in the airways, contributing to narrowing of the airways and causing a cough with sputum. Microscopically there is infiltration of the airway walls with inflammatory cells. Inflammation is followed by scarring and remodeling that thickens the walls and also results in narrowing of the airways. As chronic bronchitis progresses, there is squamous metaplasia (an abnormal change in the tissue lining the inside of the airway) and fibrosis (further thickening and scarring of the airway wall). The consequence of these changes is a limitation of airflow.
Patients with advanced COPD that have primarily chronic bronchitis rather than emphysema were commonly referred to as “Blue Bloaters” because of the bluish color of the skin and lips (cyanosis) along with hypoxia and fluid retention seen in them.
Lung damage and inflammation of the air sacs (alveoli) causes emphysema. Emphysema is an enlargement of the air spaces distal to the terminal bronchioles, with destruction of their walls. The destruction of air space walls reduces the surface area available for the exchange of oxygen and carbon dioxide during breathing. It also reduces the elasticity of the lung itself, which results in a loss of support for the airways that are embedded in the lung. These airways are more likely to collapse causing further limitation to airflow. These people are also known as “Pink Puffers”, due to their pink complexion.
There are 4 types of emphysema:
- Centriacinar / centrilobular: proximal to central parts of acini (air spaces closer to bronchioles) are affected
- Panacinar / panlobular: enlargement of all air spaces (from bronchioles to terminal blind alveoli). This type is associated with alpha-1-antitrypsin deficiency
- Distal acinar / paraseptal: proximal acinus normal, distal acinus affected
- Irregular: various parts of acinus involved. Associated with fibrosis.
Cause of COPD
The primary risk factor for COPD is chronic tobacco smoking. Exposure to cigarette smoke is measured in pack-years, the average number of packages of cigarettes smoked daily multiplied by the number of years of smoking. The likelihood of developing COPD increases with age and cumulative smoke exposure, and almost all lifelong smokers will develop COPD, provided that smoking-related, extrapulmonary diseases (cardiovascular, diabetes, cancer) do not claim their lives beforehand.
Intense and prolonged exposure to workplace dusts found in coal mining, gold mining, and the cotton textile industry and chemicals such as cadmium, isocyanates, and fumes from welding have been implicated in the development of airflow obstruction, even in nonsmokers. Workers who smoke and are exposed to these particles and gases are even more likely to develop COPD. Intense silica dust exposure causes silicosis, a restrictive lung disease distinct from COPD; however, less intense silica dust exposures have been linked to a COPD-like condition. The effect of occupational pollutants on the lungs appears substantially less important than the effect of cigarette smoking.
Studies in many countries have found people who live in large cities have a higher rate of COPD compared to people who live in rural areas. Urban air pollution may be a contributing factor for COPD, as it is thought to slow the normal growth of the lungs, although the long-term research needed to confirm the link has not been done. Studies of the industrial waste gas and COPD/asthma-aggravating compound, sulfur dioxide, and the inverse relation to the presence of the blue lichen Xanthoria (usually found abundantly in the countryside, but never in towns or cities) have been seen to suggest combustive industrial processes do not aid COPD sufferers. In many developing countries, indoor air pollution from cooking fire smoke (often using biomass fuels such as wood and animal dung) is a common cause of COPD, especially in women.
Some factor in addition to heavy smoke exposure is required for a person to develop COPD. This factor is probably a genetic susceptibility. COPD is more common among relatives of COPD patients who smoke than unrelated smokers. The genetic differences that make some peoples’ lungs susceptible to the effects of tobacco smoke are mostly unknown. Alpha 1-antitrypsin deficiency is a genetic condition that is responsible for about 2% of cases of COPD. In this condition, the body does not make enough of a protein, alpha 1-antitrypsin. Alpha 1-antitrypsin protects the lungs from damage caused by protease enzymes, such as elastase and trypsin, that can be released as a result of an inflammatory response to tobacco smoke.
There is mounting evidence that there may be an autoimmune component to COPD, triggered by lifelong smoking. Many individuals with COPD who have stopped smoking have active inflammation in the lungs. The disease may continue to get worse for many years after stopping smoking due to this ongoing inflammation. This sustained inflammation is thought to be mediated by autoantibodies and autoreactive T cells.
An acute exacerbation of COPD is a sudden worsening of COPD symptoms (shortness of breath, quantity and color of phlegm) that typically lasts for several days. It may be triggered by an infection with bacteria or viruses or by environmental pollutants. Typically, infections cause 75% or more of the exacerbations; bacteria can be found in roughly 25% of cases, viruses in another 25%, and both viruses and bacteria in another 25%. Pulmonary emboli can also cause exacerbations of COPD. Airway inflammation is increased during the exacerbation, resulting in increased hyperinflation, reduced expiratory air flow and worsening of gas transfer. This can also lead to hypoventilation and eventually hypoxia, insufficient tissue perfusion, and then cell necrosis.
Other risk factors
Bronchial hyperresponsiveness, is a characteristic of asthma and refers to the increased sensitivity of the airways in response to an inhaled constrictor agonist. Many people with COPD also have this tendency. In COPD, the presence of bronchial hyperresponsiveness predicts a worse course of the disease. It is not known if bronchial hyperresponsiveness is a cause or a consequence of COPD. Other risk factors such as repeated lung infection and possibly a diet high in cured meats (possibly due to the preservative sodium nitrite) may be related to the development of COPD.
Signs and Symptoms of COPD
Essentials of diagnosis include:
- History of tobacco smoking.
- Chronic cough and sputum production (in chronic bronchitis)
- Rhonchi, decreased intensity of breath sounds, and prolonged expiration on physical examination
- Airflow limitation on pulmonary function testing that is not fully reversible and most often progressive.
One of the most common symptoms of COPD is shortness of breath (dyspnea). People with COPD commonly describe this as: “My breathing requires effort,” “I feel out of breath,” or “I can’t get enough air in”. People with COPD typically first notice dyspnea during vigorous exercise when the demands on the lungs are greatest. Over the years, dyspnea tends to get gradually worse so that it can occur during milder, everyday activities such as housework. In the advanced stages of COPD, dyspnea can become so bad that it occurs during rest and is constantly present.
Other symptoms of COPD are a persistent cough, sputum or mucus production, wheezing, chest tightness, and tiredness.
People with advanced COPD sometimes develop respiratory failure. When this happens, cyanosis, a bluish discoloration of the lips caused by a lack of oxygen in the blood, can occur. An excess of carbon dioxide in the blood can cause headaches, drowsiness or twitching (asterixis). A complication of advanced COPD is cor pulmonale, a strain on the heart due to the extra work required by the heart to pump blood through the affected lungs. Symptoms of cor pulmonale are peripheral edema, seen as swelling of the ankles, and dyspnea. Clubbing is usually not directly attributable to COPD and should indeed prompt investigations for an underlying lung cancer.
There are a few signs of COPD that a healthcare worker may detect although they can be seen in other diseases. Some people have COPD and have none of these signs. Common signs are:
- tachypnea, a rapid breathing rate
- wheezing sounds or crackles in the lungs heard through a stethoscope
- breathing out taking a longer time than breathing in
- enlargement of the chest, particularly the front-to-back distance (hyperaeration)
- active use of muscles in the neck to help with breathing
- breathing through pursed lips
- increased anteroposterior to lateral ratio of the chest (i.e. barrel chest).
Risk Factors for COPD
Risk factors for COPD include:
-Exposure to tobacco smoke. The most significant risk factor for COPD is long-term cigarette smoking. The more years you smoke and the more packs you smoke, the greater your risk. Pipe smokers, cigar smokers, marijuana smokers and people exposed to large amounts of secondhand smoke also are at risk.
-People with asthma who smoke. The combination of asthma, a chronic airway disease, and smoking increases the risk of COPD even more.
-Occupational exposure to dusts and chemicals. Long-term exposure to chemical fumes, vapors and dusts in the workplace can irritate and inflame your lungs. Urban air pollution may be a contributing factor for COPD, as it is thought to slow the normal growth of the lungs, although the long-term research needed to confirm the link has not been done.
-Age. COPD develops slowly over years, so most people are at least 35 to 40 years old when symptoms begin.
-Genetics. Some factor in addition to heavy smoke exposure is required for a person to develop COPD. This factor is probably a genetic susceptibility. COPD is more common among relatives of COPD patients who smoke than unrelated smokers. The genetic differences that make some peoples’ lungs susceptible to the effects of tobacco smoke are mostly unknown. Alpha 1-antitrypsin deficiency is a genetic condition that is responsible for about 2% of cases of COPD. In this condition, the body does not make enough of a protein, alpha 1-antitrypsin. Alpha 1-antitrypsin protects the lungs from damage caused by protease enzymes, such as elastase and trypsin, that can be released as a result of an inflammatory response to tobacco smoke.
Diagnosis of COPD
The diagnosis of COPD should be considered in anyone who has dyspnea, chronic cough or sputum production, and/or a history of exposure to risk factors for the disease such as regular tobacco smoking. No single symptom or sign can adequately confirm or exclude the diagnosis of COPD, although COPD is uncommon under the age of 40 years.
The diagnosis of COPD is confirmed by spirometry, a test that measures the forced expiratory volume in one second (FEV1), which is the greatest volume of air that can be breathed out in the first second of a large breath. Spirometry also measures the forced vital capacity (FVC), which is the greatest volume of air that can be breathed out in a whole large breath. Normally, at least 70% of the FVC comes out in the first second (i.e. theFEV1/FVC ratio is >70%). A ratio less than normal defines the patient as having COPD. More specifically, the diagnosis of COPD is made when the FEV1/FVC ratio is <70%. The GOLD criteria (Global Initiative for Chronic Obstructive Lung Disease) also require that values are after bronchodilatormedication has been given to make the diagnosis, and the NICE criteria also require FEV1%. According to the ERS criteria, it is FEV1% predictedthat defines when a patient has COPD, that is, when FEV1% predicted is < 88% for men, or < 89% for women.
Spirometry can help to determine the severity of COPD. The FEV1 (measured after bronchodilator medication) is expressed as a percentage of a predicted “normal” value based on a person’s age, gender, height and weight:
The severity of COPD also depends on the severity of dyspnea and exercise limitation. These and other factors can be combined with spirometry results to obtain a COPD severity score that takes multiple dimensions of the disease into account.
On chest x-ray, the classic signs of COPD are overexpanded lung (hyperinflation), a flattened diaphragm, increased retrosternal airspace, and bullae. It can be useful to help exclude other lung diseases, such as pneumonia, pulmonary edema or a pneumothorax. Complete pulmonary function tests with measurements of lung volumes and gas transfer may also show hyperinflation and can discriminate between COPD with emphysema and COPD without emphysema. A high-resolution computed tomography scan of the chest may show the distribution of emphysema throughout the lungs and can also be useful to exclude other lung diseases.
A blood sample taken from an artery, i.e. Arterial Blood Gas (ABG), can be tested for blood gas levels which may show low oxygen (hypoxaemia) and/or high carbon dioxide (respiratory acidosis if pH is also decreased). A blood sample taken from a vein may show a high blood count (reactive polycythemia), a reaction to long-term hypoxemia.
Prevention from COPD
If you are concerned about getting COPD, there are steps you can take to protect yourself.
- If you are a smoker, STOP SMOKING. Quitting smoking is the single most important thing a smoker can do to live a longer and healthier life. There are clear benefits to quitting, even after years of smoking. When you stop smoking, you slow down the damage to your lungs. For most people who quit, loss of lung function is slowed to the same rate as a nonsmoker’s.
- If you don’t smoke, don’t start. Smoking causes COPD, lung cancer, heart disease, and other cancers.
- Avoid exposure to secondhand smoke. Make your home smoke-free. You’ll not only protect yourself, but your family, too. Learn about your rights to a smoke-free environment at work and in public places.
- Occupational exposure to chemical fumes and dust is another risk factor for COPD. If you work with this type of lung irritant, talk to your supervisor about the best ways to protect yourself, such as using respiratory protective equipment.
- If you have COPD, you need to get a flu vaccine every year. When people with COPD get the flu, it often turns into something more serious, like pneumonia.
- People with COPD often get pneumonia. Getting a shot can help keep you from getting very ill with pneumonia.
Treatment of COPD
There is currently no cure for COPD; however, COPD is both preventable and treatable.Clinical practice guidelines for the management of COPD are available from the Global Initiative for Chronic Obstructive Lung Disease (GOLD), a collaboration that includes the World Health Organization and the U.S. National Heart, Lung, and Blood Institute. The major current directions of COPD management are to assess and monitor the disease, reduce the risk factors, manage stable COPD, prevent and treat acute exacerbations and manage comorbidity.
The only measures that have been shown to reduce mortality is smoking cessation and supplemental oxygen.
Bronchodilators are medicines that relax smooth muscle around the airways, increasing the calibre of the airways and improving air flow. They can reduce the symptoms of shortness of breath, wheeze and exercise limitation, resulting in an improved quality of life for people with COPD. They do not slow down the rate of progression of the underlying disease. Bronchodilators are usually administered with an inhaler or via a nebulizer.
There are two major types of bronchodilator, β2 agonists and anticholinergics. Anticholinergics appear superior to β2 agonists in COPD. Anticholinergics reduce respiratory deaths while β2agonists have no effect on respiratory deaths. Each type may be either long-acting (with an effect lasting 12 hours or more) or short-acting (with a rapid onset of effect that does not last as long).
β2 agonists stimulate β2 receptors on airway smooth muscles, causing them to relax. There are several β2 agonists available. Salbutamol (common brand name: Ventolin) and terbutaline are widely used short acting β2 agonists and provide rapid relief of COPD symptoms. Long acting β2 agonists (LABAs) such as salmeterol and formoterol are used as maintenance therapy and lead to improved airflow, exercise capacity, and quality of life.
Anticholinergic drugs cause airway smooth muscles to relax by blocking stimulation from cholinergic nerves. Ipratropium provides short-acting rapid relief of COPD symptoms. Tiotropium is a long-acting anticholinergic whose regular use is associated with improvements in airflow, exercise capacity, and quality of life. Ipratropium is associated with increased cardiovascular morbidity.
While tiotropium in pill form reduces the risk of all cause mortality, cardiovascular mortality and cardiovascular events that in mist form increases mortality.
Corticosteroids are used in tablet or inhaled form to treat and prevent acute exacerbations of COPD. Well-inhaled corticosteroids (ICS) have not shown benefit for people with mild COPD, however, they have been shown to decrease acute exacerbations in those with either moderate or severe COPD. They however have no effect on overall one-year mortality and are associated with increased rates of pneumonia.
Antibiotics specifically macrolides such as azithromycin reduce the number of exacerbations in those who have two or more a year.
Theophylline is a bronchodilator and phosphodiesterase inhibitor that in high doses can reduce symptoms for some people who have COPD. More often, side effects such as nausea and stimulation of the heart limit its use.
Supplemental oxygen or oxygen therapy can improve oxygen saturation levels, allowing patients with COPD or low oxygen levels to maintain their mobility and increase their ability to complete activities of daily living (ADL), such as exercise, household chores, shopping, etc. Long-term oxygen therapy for at least 16 hours a day can improve the quality of life and survival for people with COPD and arterial hypoxemia or with complications of hypoxemia such as pulmonary hypertension, cor pulmonale, or secondary erythrocytosis. High concentrations of supplemental oxygen can lead to the accumulation of carbon dioxide and respiratory acidosis for some people with severe COPD; lower oxygen flow rates are generally safer for these individuals. Another safety issue concerning the use of oxygen for patients with COPD is smoking, because oxygen can act as an oxidizing agent.
Pulmonary rehabilitation is a program of exercise, disease management and counselling coordinated to benefit the individual. Pulmonary rehabilitation has been shown to improve shortness of breath and exercise capacity. It has also been shown to improve the sense of control a patient has over their disease as well as their emotions.
Being either underweight or overweight can affect the symptoms, degree of disability and prognosis of COPD. People with COPD who are underweight can improve their breathing muscle strength by increasing their calorie intake. When combined with regular exercise or a pulmonary rehabilitation programme, this can lead to improvements in COPD symptoms.
Surgery is sometimes helpful for COPD in selected cases. A bullectomy is the surgical removal of a bulla, a large air-filled space that can squash the surrounding, more normal lung. Lung volume reduction surgery is similar; parts of the lung that are particularly damaged by emphysema are removed allowing the remaining, relatively good lung to expand and work better. Lung transplantation is sometimes performed for severe COPD, particularly in younger individuals.
Obesity, poor nutrition, depression and social isolation are looked at. Palliative care for end of life needs is important. Morphine and benzodiazepines are used in low doses to reduce anxiety. In advanced critical illness, decisions about resuscitation are addressed. Infliximab has been tested in COPD but there was no evidence of benefit with the possibility of harm.