Alternative names
Chronic Obstructive Airway Disease (COAD); Chronic Obstructive Lung Disease (COLD)
What is chronic obstructive pulmonary disease?
Chronic obstructive pulmonary disease (COPD) is a collective name, and includes conditions such as chronic bronchitis, emphysema and cystic fibrosis.
Chronic bronchitis refers to the inflammatory reaction in the small and large airway walls, while emphysema involves the delicate gas exchange part of the lung, the tiny sacs called alveoli. Destruction of these delicate structures leads to large non-functional spaces in the lungs known as bullae, which have a limited to non-existent capacity to take up oxygen, with subsequent severe exercise impairment in affected individuals.
Chronic obstructive pulmonary disease, as the name suggests, is characterised by obstructive airflow into and out of the lungs, which can only be partially resolved with standard medication. The ongoing inflammatory response in the airways leads to mucus over-production and inflammatory swelling of the inner layers of the airways, with subsequent obstruction to airflow. Chronic inhalation of noxious particles and gases will stimulate this state of inflammation.
The cells involved in the inflammatory response are the normal white cells (neutrophils and macrophages), which should protect the body during infective challenges. The normal defence mechanism of the body, which is aimed primarily at mopping up the invasive substances, attacks normal lung tissue to the detriment of the respiratory system. Thickening of the bronchial walls, formation of scar tissue and eventual destruction of the minute alveoli, which are responsible for oxygen uptake, will not only impair airflow, but also the uptake of life-sustaining oxygen and removal of carbon dioxide. The inflammatory response will periodically flare up during attacks of influenza and bronchitis, during which period patients may become acutely ill and very short of breath.
A characteristic of the inflammatory response of COPD is that it is not responsive to long-term medication with drugs such as corticosteroids, which are used successfully for prevention of asthma. When the inflammatory response has, over a period of years, caused extensive damage to the small airways and alveoli, patients will present with respiratory failure due to lack of oxygenation, or right heart failure (See Symptoms and diagnosis of COPD).
The disease is not confined to the lungs; it has systemic (whole body) effects that result in, for example, weight and appetite loss, and particularly a decrease of muscle mass in the limbs in severely ill patients. This leads to a vicious circle, as weakened patients who are extremely short of breath tend to withdraw, become completely inactive and frequently die in isolation.
Who gets COPD and who is at risk?
COPD primarily affects adults over 45 years of age, and rates as one of the major causes of death world-wide. The World Health Organisation rates COPD as the fourth most common cause of death throughout the world. An alarming rise in the prevalence of this condition, particularly among women, indicates that mortality and morbidity (illness) due to COPD may be much higher by 2020.
Patients with this condition experience a prolonged decline of exercise capacity and in the final years of their life are severely dyspnoeic (short of breath), often unable to lead a normal life and needing to be maintained on continuous medical support systems and therapy. This incurs great personal and national expense, which in the USA amounted to a total cost of $23.9 billion in 1993. (By comparison, the total bill for asthma was $12.6 billion and pneumonia $7.8 billion.) The financial burden of COPD, particularly in developing countries, will parallel the ongoing abuse of factors that cause the disease, such as smoking.
Reversing this trend will take time: the effects of successful public education programmes will only be noticed in several decades, given that the negative effects of smoking become apparent 30-40 years after its onset.
Risk Factors
Host factors
- Genes (e.g. alpha-1 antitrypsin deficiency)
- Airway Hyper-responsiveness
- Lung growth
Exposure
- Tobacco smoke
- Occupational dusts and chemicals
- Indoor and outdoor air pollution
- Infections
- Socio-economic status
The role of tobacco smoke as a causative agent for COPD has been proven beyond all doubt. It appears that starting smoking at a young age, the "total pack years" (the number of cigarettes smoked per year multiplied by the number of years of smoking) and the person's current smoking status all contribute to the final state of respiratory impairment due to COPD. In spite of this, only an estimated 20% of smokers develop the disease. However, this figure does not take into consideration the combined effect of several other risk factors that commonly occur in individuals in underprivileged communities, with a subsequent greater likelihood of developing the disease.
Evidence has been found that secondary cigarette smoke can cause COPD in non-smoking bystanders. This has serious health and legal implications, as smokers could jeopardise the health of the non-smoking population.
In a number of occupations, including mining and industry, dust and exposure to welding gases and fumes have been associated with the development of COPD. Enforcement of protective measures in the workplace, including wearing masks and monitoring levels of dust and toxic fumes, have minimised and in some cases abolished the danger of industrial exposure.
Low socio-economic status is a risk factor for the development of COPD due to the high prevalence of other risk factors, including secondary cigarette smoke exposure, particularly in childhood; and tuberculosis, which tends to occur in deprived communities. Good evidence has been found that tuberculosis (TB), particularly recurrent episodes of the disease, leads to the development of COPD in up to 30% of patients in developing countries. Additional risk factors in disadvantaged communities include the indoor burning of biomass fuels and a tendency to recurrent chest infections, which in their own right cause further damage to the bronchial walls and contribute to the onset of COPD. In these communities, children of parents who smoke are at a proven disadvantage, as recurrent chest infections and impaired lung growth predispose these unfortunate individuals to early development of COPD.
The fact that many industrial workers and miners smoke and contract tuberculosis serves as one example of how combinations of risk factors contribute through a final common pathway of airway inflammation to create an accumulative burden for causing COPD.
It should be evident that as long as these risk factors prevail in communities, the disease prevalence will continue its upward spiral and continue to be a major burden on national and personal health budgets.
Asthmatics and COPD
Young asthmatics who smoke or who are exposed to noxious agents in the workplace tend to have an early onset of COPD. A common mistake, however, is to label wheezy COPD patients as asthmatics. Asthma is a disease that tends to have its onset in the teens or early adulthood, is usually associated with hay fever and is caused by readily definable antigens that induce attacks of airway obstruction. (For the sake of specific treatment, the attending physician has to make a decision of where asthma ends and COPD starts). Treatment and prognosis for asthma is completely different to that for COPD, with a favourable response to treatment in asthmatics and less so in COPD patients.
Symptoms and diagnosis of COPD
In spite the well-known risk factors, the majority of COPD patients (up to 70%) remain undiagnosed. In the early phases, patients may cough with sputum production but may not be physically active enough for their shortness of breath to become evident. It is only by a regular measurement of lung functions in patients at risk, that the disease will be unmasked in its early stages.
Patients at risk should request that their doctors do lung function measurements, which include the forced expiratory volume in one second (FEV1), vital capacity (VC) and the FEV1/VC ratio. It is only when lung function deteriorates to a measured FEV1 of less than 50% of the predicted value that patients experience severe enough symptoms to report their respiratory impairment.
The importance of early diagnosis is that preventative measures, including avoidance of risk factors, can be instituted. This will have major long-term benefits for affected individuals.
A diagnosis of COPD should be considered in any patient who has a chronic cough, sputum production, shortness of breath and/or history of exposure to risk factors. The diagnosis is confirmed by lung function testing.
Disease symptoms are frequently initiated by a severe attack of bronchitis, usually during the wintertime when influenza and colds are endemic. These patients commonly complain of an irritating persistent cough accompanied by sputum production or a wheeze.
Smokers usually have a much longer recovery time than non-smokers and experience more severe symptoms during acute exacerbations of COPD.
In patients with severe respiratory impairment, these attacks may lead to respiratory failure. Oxygenation becomes so limited that a blue tongue and lips indicate severe impairment of oxygen uptake. Acute exacerbations may also be accompanied by evidence of failure of the right ventricle to pump adequately due to increased pressure in the vascular bed of the lungs, which is characterised by swollen ankles and legs, an enlarged liver and elevated neck veins. Symptoms of respiratory and right heart failure usually justify admission to hospital. Active treatment of these conditions can reverse the heart or lung failure, while identification of factors that cause exacerbation e.g. respiratory infections; fluid overload or lung clots should be remedied, thereby preventing further acute incidents.
Treatment and monitoring of COPD
No curative treatment for COPD exists. Cessation of smoking is the only significant therapeutic measure, which will retard chronic loss of lung function.
Treatment of COPD depends on the severity of the condition with which patients present to their general practitioners and physicians.
Mild disease
Patients with risk factors may present with limited symptoms, which manifest after acute upper airway and chest infections. Management of the risk factors, particularly cessation of smoking, is an important preventative component of these patients' treatment. The use of short-acting bronchodilator therapy (medications to dilate the bronchial airways), such as the well-known asthma inhalers, will provide temporary relief during episodes of wheezing.
Vaccination of these individuals against the predominant viral strains is important.
Patients must be informed that secondary cigarette smoke, as well as exposure to noxious fumes, gases and dust at work needs to be addressed to preserve respiratory function.
Moderate disease
These patients are clearly symptomatic and should be similarly approached as regards risk factors and vaccination. Regular prophylactic treatment with oral and inhaled preparations should be applied in this group of patients. There is no evidence that long-term treatment with steroids will prevent a loss of lung function over time. Subsequently, patients who may benefit from long-term corticosteroid treatment and who may develop side-effects of the drug should be carefully monitored.
Severe COPD
These patients are severely symptomatic and have usually had one or more incidents of respiratory or right heart failure. Severe respiratory impairment, a clear loss of lung function and a limited response to preventative treatment identifies these unfortunate individuals.
Rehabilitation is an important component of treatment in this group. This relates to strengthening the arm and leg muscles as well as the muscles of inspiration, which enable patients to carry on with their daily routine in spite of considerable loss of lung function. This state of “fitness” is only achieved after an intensive rehabilitation programme, which has to be conducted under supervision.
Continuous home oxygen has been shown to decrease mortality and morbidity of patients with respiratory failure and COPD. Oxygen devices that operate through home power sources generate enough oxygen to support patients for an essential 16 hours per day. This treatment provides wonderful symptomatic relief.
A type of surgery known as lung volume reduction surgery was previously offered to patients with COPD, but was not found to be a long-term solution as symptoms tended to recur five years after the operation.
Education about COPD
The battle for prevention of COPD will be won or lost depending on the education those health authorities, doctors and the media provide to the public about COPD. Preventing smoking at school level is a much more cost-effective method of combating the disease than trying to convert smokers or treating symptoms when they occur.
The management and treatment of patients with COPD has frequently been met with a very nihilistic attitude by health providers. The argument that it is a self-induced, progressive disease, for which treatment does not make a difference, needs to be replaced with a new and an enthusiastic approach to the problem.
Much has changed during recent years in terms of understanding and preventing the disease, and in its rational treatment, which may alleviate the suffering of a large number of patients. Clearly, education of health authorities, health workers and the public will contribute to a decreasing prevalence of this much neglected condition.
Written by Prof J.R. Joubert, MSc, MBChB (Stell), FCP (SA), MMed (Int. Med), MD (Stell).
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