Chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease is a type of progressive lung disease characterized by chronic respiratory symptoms and airflow limitation. GOLD defines COPD as a heterogeneous lung condition characterized by chronic respiratory symptoms due to abnormalities of the airways or alveoli that cause persistent, often progressive, airflow obstruction.
The main symptoms of COPD include shortness of breath and a cough, which may or may not produce mucus. COPD progressively worsens, with everyday activities such as walking or dressing becoming difficult. While COPD is incurable, it is preventable and treatable. The two most common types of COPD are emphysema and chronic bronchitis, and have been the two classic COPD phenotypes. However, this basic dogma has been challenged as varying degrees of co-existing emphysema, chronic bronchitis, and potentially significant vascular diseases have all been acknowledged in those with COPD, giving rise to the classification of other phenotypes or subtypes.
Emphysema is defined as enlarged airspaces whose walls have broken down, resulting in permanent damage to the lung tissue. Chronic bronchitis is defined as a productive cough that is present for at least three months each year for two years. Both of these conditions can exist without airflow limitations when they are not classed as COPD. Emphysema is just one of the structural abnormalities that can limit airflow and can exist without airflow limitation in a significant number of people. Chronic bronchitis does not always result in airflow limitation. However, in young adults with chronic bronchitis who smoke, the risk of developing COPD is high. Many definitions of COPD in the past included emphysema and chronic bronchitis, but these have never been included in GOLD report definitions. Emphysema and chronic bronchitis remain the predominant phenotypes of COPD, but there is often overlap between them, and several other phenotypes have also been described. COPD and asthma may coexist and converge in some individuals. COPD is associated with low-grade systemic inflammation.
The most common cause of COPD is tobacco smoking. Other risk factors include indoor and outdoor air pollution including dust, exposure to occupational irritants such as dust from grains, cadmium dust or fumes, and genetics, such as alpha-1 antitrypsin deficiency. In developing countries, common sources of household air pollution are the use of coal and biomass such as wood and dry dung as fuel for cooking and heating. The diagnosis is based on poor airflow as measured by spirometry.
Most cases of COPD can be prevented by reducing exposure to risk factors such as smoking and indoor and outdoor pollutants. While treatment can slow worsening, there is no conclusive evidence that any medications can change the long-term decline in lung function. COPD treatments include smoking cessation, vaccinations, pulmonary rehabilitation, inhaled bronchodilators and corticosteroids. Some people may benefit from long-term oxygen therapy, lung volume reduction and lung transplantation. In those who have periods of acute worsening, increased use of medications, antibiotics, corticosteroids and hospitalization may be needed.
As of 2021, COPD affected about 213 million people. It typically occurs in males and females over the age of 35–40. In 2021, COPD caused 3.65 million deaths. Almost 90% of COPD deaths in those under 70 years of age occur in low and middle income countries. In 2021, it was the fourth biggest cause of death, responsible for approximately 5% of total deaths. The number of deaths is projected to increase further because of continued exposure to risk factors and an aging population. In the United States, costs of the disease were estimated in 2010 at $50 billion, most of which is due to exacerbation.
Signs and symptoms
Shortness of breath
A cardinal symptom of COPD is the chronic and progressive shortness of breath which is most characteristic of the condition. Shortness of breath is often the most distressing symptom, responsible for the associated anxiety and level of disability experienced. Symptoms of wheezing and chest tightness associated with breathlessness can be variable over the course of a day or between days and are not always present. Chest tightness often follows exertion. Many people with more advanced COPD breathe through pursed lips, which can improve shortness of breath. Shortness of breath is often responsible for reduced physical activity, and low levels of physical activity are associated with worse outcomes. In severe and very severe cases there may be constant tiredness, weight loss, muscle loss and anorexia. People with COPD often have increased breathlessness and frequent colds before seeking treatment.Cough
The most often first symptom of COPD is a chronic cough, which may or may not be productive of mucus as phlegm. Phlegm coughed up as sputum can be intermittent and may be swallowed or spat out depending on social or cultural factors, and is therefore not always easy to evaluate. However, an accompanying productive cough is only seen in up to 30% of cases. Sometimes, limited airflow may develop in the absence of a cough. Symptoms are usually worse in the morning.A chronic productive cough is the result of mucus hypersecretion, and when it persists for more than three months each year for at least two years, it is defined as chronic bronchitis. Chronic bronchitis can occur before the restricted airflow diagnostic of COPD. Some people with COPD attribute the symptoms to the consequences of smoking. In severe COPD, vigorous coughing may lead to rib fractures or to a brief loss of consciousness.
Exacerbations
An acute exacerbation is a sudden worsening of signs and symptoms that lasts for several days. The key symptom is increased breathlessness; other more pronounced symptoms are of excessive mucus, increased cough and wheeze. A commonly found sign is air trapping, giving difficulty in complete exhalation. The usual cause of an exacerbation is a viral infection, most often the common cold. The common cold is usually associated with the winter months but can occur at any time. Other respiratory infections may be bacterial or in combination sometimes secondary to a viral infection. The most common bacterial infection is caused by Haemophilus influenzae. Other risks include exposure to tobacco smoke and environmental pollutantsboth indoor and outdoor. During the COVID-19 pandemic, hospital admissions for COPD exacerbations sharply decreased which may be attributable to reduction of emissions and cleaner air. There has also been a marked decrease in the number of cold and flu infections during this time.Smoke from wildfires is proving an increasing risk in many parts of the world, and government agencies have published protective advice on their websites. In the US the EPA advises that the use of dust masks does not give protection from the fine particles in wildfires and instead advises the use of well-fitting particulate masks. This same advice is offered in Canada and Australia to the effects of their forest fires.
The number of exacerbations is not seen to relate to any stage of the disease; those with two or more a year are classed as frequent exacerbators and these lead to a worsening in the disease progression. Frailty in ageing increases exacerbations and hospitalization.
Acute exacerbations in COPD are often unexplained and thought to have many causes other than infections. A study has emphasized the possibility of a pulmonary embolism as sometimes being responsible in these cases. Signs can include pleuritic chest pain and heart failure without signs of infection. Such emboli could respond to anticoagulants.
Other conditions
COPD often occurs along with several other conditions due in part to shared risk factors. Common comorbidities include cardiovascular disease, skeletal muscle dysfunction, metabolic syndrome, osteoporosis, depression, anxiety, asthma and lung cancer. Alpha-1 antitrypsin deficiency is an important risk factor for COPD. It is advised that everybody with COPD be screened for A1AD. Metabolic syndrome has been seen to affect up to fifty percent of those with COPD and significantly affects the outcomes. When comorbid with COPD there is more systemic inflammation. It is not known if it co-exists with COPD or develops as a consequence of the pathology. Metabolic syndrome on its own has a high rate of morbidity and mortality, and this rate is amplified when comorbid with COPD. Tuberculosis is a risk factor for the development of COPD, and is also a potential comorbidity. Most people with COPD die from comorbidities and not from respiratory problems.Anxiety and depression are often complications of COPD. Other complications include reduced quality of life and increased disability, cor pulmonale, frequent chest infections including pneumonia, secondary polycythemia, respiratory failure, pneumothorax, lung cancer, and cachexia.
Along with these complications, there is an associated risk of developing pulmonary hypertension. The estimated prevalence of pulmonary hypertension complicating COPD was reported at 39% in a meta-analysis. Of the people with COPD listed for lung transplantation, 82% were documented as having pulmonary hypertension via right heart catheterization, noting a mean pulmonary arterial pressure greater than 20mm Hg. Despite pulmonary hypertension being relatively rare in people with COPD, mild elevations of pulmonary arterial pressure can lead to worse outcomes, including risk of death.
Cognitive impairment is common in those with COPD, as it is for other lung conditions that affect airflow. Cognitive impairment is associated with the declining ability to cope with the basic activities of daily living.
It is unclear if those with COPD are at greater risk of contracting COVID-19, though if infected, they are at risk of hospitalization and developing severe COVID-19. However, laboratory and clinical studies are showing a possibility of certain inhaled corticosteroids for COPD providing a protective role against COVID-19.
Differentiating COVID-19 symptoms from an exacerbation is difficult; mild prodromal symptoms may delay its recognition, and where they include loss of taste or smell, COVID-19 is to be suspected.