COPD: obstructed lungs.
Treating exacerbations, improving exercise capacity, and delaying progression of disease are key management strategies. No curative or disease modifying therapies are available. Nurses are essential in providing comprehensive care to patients in both acute care and for long-term management. They also have a vital role to play in preserving healthy lung function in the early years of life to reduce the risk of COPD in older age.
Chronic obstructive pulmonary disease (COPD) describes a spectrum of respiratory illnesses where airflow is irreversibly limited, impairing gas exchange in the alveoli. COPD covers three respiratory diseases: chronic bronchitis, small airways disease (chronic bronchiolitis) and emphysema, and there may be a component of asthma in some cases. While genetic factors predispose people to COPD, acquisition of the disease is driven by exposure to risk factors throughout the lifespan.
Worldwide, the prevalence of COPD is 8.5 per cent in women and 11.8 per cent in men, but rates in women are increasing. (1) These prevalence rates are probably underestimated because people do not usually present with the disease until it is in the later stages. One in five people who have smoked for longer than 10 years probably have COPD. (1) The global burden of COPD is set to rise due to ageing populations, high rates of smoking, and, in some regions, increasing air pollution. (2)
In New Zealand, COPD affects 14 per cent of the population over 40, and is the fourth leading cause of death in both men and women. (4,5)
Hospital care for people with COPD cost almost $60 million in the 2012/13 year, with peak admissions in late winter. Thirty-three per cent of patients are readmitted within 30 days of discharge. (5)
COPD disproportionately affects Maori. Rates of hospitalisation are 4.4 times higher for Maori, and 3.6 times higher for Pacific COPD patients than European and other ethnicities. (5) The mortality rate from COPD in Maori is twice that for non-Maori. (4)
COPD is responsible for loss of quality of life and income. The social and economic costs for an individual depend on the severity of the disease, frequency of exacerbations and the presence of co-morbidities. Thirty to 57 per cent of people with COPD have concurrent debilitating illnesses, eg heart disease, lung cancer, pneumonia and depression. (2,4) People with COPD are likely to lose more life-years to disability and to die prematurely than those without. Apart from direct costs (such as hospitalisation, tests and investigations, medications, and GP and outpatient visits), there are indirect costs for patients and caregivers due to lost productivity. These are thought to be at least equal to the direct costs of chronic illness. A further intangible cost, caused by the impact of illness on quality of life, is sustained by patients and their families (eg, costs associated with pain and grief), but this is less readily calculated. (6)
CAUSES OF COPD
The cause of COPD is a complex interaction between genetic predisposition and exposure to environmental conditions that increase risk, and can occur at any time from before birth through adulthood (see Figure 1, p23). Cigarette smoking is the most recognised risk factor for COPD. Age is considered a risk factor, as risk increases with age. But it is not known if ageing itself is to blame, or rather the accumulation of repeated lung insults through a long lifespan. (3)
Early childhood disadvantage--at least one of: maternal smoking; childhood respiratory infections; or maternal, paternal or childhood asthma--carries as much risk for COPD as smoking in adult life. However, epidemiological relationships like this cannot determine cause or effect. (7)
There is an identified association in rates of COPD between family members (regardless of tobacco exposure), which indicates underlying genetic influences. A very small number of people with emphysema have a hereditary defect in the genes responsible for producing alpha-1-antitrypsin and this was the first genetic association with COPD to be determined.
More recently, a number of genes involved in regulating enzyme activity and receptor function have been linked to COPD, but none conclusively. Genes that protect the lungs from damage following exposure to tobacco smoke have been identified as abnormal in people with COPD. These include genes regulating cell and oxidative stress responses, inflammation, arsenic biotransformation, nicotine dependence, lung development and repair, alveolar development, cell ageing and programmed cell death. (21) Interestingly, a genetic polymorphism has also been identified that is protective against COPD. (7)
Lung development affects risk of COPD. The maturity of the lungs at birth, the growth of the alveoli and airways from infancy to young adulthood, as well as the rate of functional decline with ageing, determine the threshold at which a person can experience respiratory symptoms and disability. (7) Poorer lung maturity and growth, especially in the first four to six years of life, mean full lung size and maturity are not attained, so functional decline with age begins from a lower starting point. (7)
Many prenatal events are now known to influence health in later life. These events can even be transgenerational. For example, a woman who smokes in pregnancy increases the risk of her grandchildren developing asthma, even if her own daughter does not smoke.? This impact is through epigenetic changes--molecules attached to DNA strands that modify gene expression, without changing the genes themselves. Epigenetic changes are not well studied in COPD, but maternal smoking, maternal exposure to air pollution (outdoor and indoor), environmental tobacco exposure, maternal diabetes, and use of paracetamol and some antibiotics in pregnancy, may cause epigenetic changes that increase the risk of COPD in the later life of the child. (7)
Healthy lungs were once considered to be a sterile environment. However, modern DNA sequencing techniques have identified a microbial (bacteria, viruses, fungi) population in the respiratory tract, referred to as a microbiome. Like the gut microbiome, lung micro-organisms interact with their host to influence growth and development, and immune function. (9) Also like the gut, the respiratory microbiome is established at birth, with different bacterial populations arising following either vaginal or caesarean delivery. It is possible that diet after birth--breast or bottle feeding--has a similar impact, but the lung microbiome appears to establish and stabilise much more rapidly than that of the gut. (9)
The composition of the lung microbiome is affected by many factors and varies significantly between lungs of healthy people and those with chronic lung conditions such as COPD. Antibiotic use disrupts the normal microbiota and may allow superinfection by pathogens. While these changes are usually temporary, early-life exposure or repeated administration of antibiotics can cause permanent change to the microbiome. (9) This, in turn, can affect immune function, eg by changing the default immune response in the airways to become more atopic, thus increasing risk of allergies, asthma and chronic inflammation. The lung microbiota is also affected by the use of inhaled bronchodilators and steroids, and some micro-organisms may even induce steroid resistance in their host cells. Disruption of the microbiota (dysbiosis) also occurs with viral infections and may be a cause of post-viral pneumonia. Damage to the respiratory tract epithelium from tobacco and air pollution also causes dysbiosis.g Dysbiosis may be a major contributor to exacerbations of COPD, especially where there are no overt signs of infection. (10)
Cigarette smoke is a complex mix of gas and microscopic particles containing more than 250 harmful chemicals (of which at least 69 are carcinogenic). (11) Exposure to environmental tobacco smoke (ETS) results in high uptake of gaseous-phase tobacco constituents, such as carbon monoxide, formaldehyde and nicotine metabolites, all of which are toxic. (12)
Maternal cigarette smoking and ETS cause abnormal lung development in utero. Animal studies show airways are longer and narrower, mucus secretion is increased and there is increased collagen in the lungs. Alveolar tethering points are decreased so the alveoli and small airways are more likely to collapse during expiration. (7)
Exposure to ETS in early childhood increases risk of cough, wheeze, respiratory infections (such as respiratory syncytial virus) and asthma. Airways become hyper-responsive, asthma tends to be worse, and atopic immune responses in the lungs are generated. Abnormal inflammatory responses may then increase the risk of developing COPD in later life. (12)
In adult smokers (and adults exposed to ETS), changes occur in the epithelium of both large and small airways well before a detectable decline in lung function. Epithelial cells show dysregulated gene expression, especially in those genes that respond to oxidative stress and that control inflammation. There is also a loss of the barrier function of the epithelium, allowing inhaled particles to cross more readily into the body. (13)
Chronic exposure to cigarette smoke causes chronic inflammation. Inflammatory cells (neutrophils, macrophages and T-lymphocytes) and cytokines accumulate in the airways, especially the bronchioles. (14) At the same time, the epithelial lining of the airways undergoes remodelling. The walls of small and large airways become thickened: cells flatten and become multi-layered; goblet (mucus-secreting) cells increase in number and size; and the smooth muscle cells underlying the epithelium also multiply and thicken. These all result in narrowing of the airway diameter. Cilia are lost, reducing the trafficking of mucus from lower airways. This is worsened by the increased size and activity of submucosal mucus-secreting glands. (14)
These changes cause development of the three diseases associated with COPD: chronic bronchiolitis, emphysema and chronic bronchitis.
CHRONIC BRONCHIOLITIS AND EMPHYSEMA
Small airways disease is likely to be the first change to occur in the development of COPD. Damage from tobacco smoke and other pollutants triggers an inflammatory cascade that narrows the small conducting airways (the bronchioles) through thickening of their walls, influx of mucus and invasion of inflammatory cells. The release of inflammatory mediators, enzymes and reactive oxygen molecules, as part of this inflammatory response, eventually causes destruction of the small airways and further inflammation. (8) Narrowing of the bronchioles is the main cause of reduced airflow through the lungs, and also contributes to air trapping during exhalation.
Emphysema contributes to the narrowing of the bronchioles. Emphysema develops when proteolytic enzymes released by inflammatory cells destroy the walls of the alveoli, including elastin and collagen fibres. Elastin provides elastic recoil in the lungs; losing elastin means the alveoli do not deflate and cannot expel respiratory gases during exhalation. Collagen provides anchoring points for the bronchioles supplying the alveoli; losing collagen causes these airways to collapse during exhalation, trapping air behind them.
As emphysema worsens, the walls of the alveoli are obliterated, along with their associated blood capillaries. Air gets trapped, leading to hyperinflation of the lungs, and gas exchange between the alveoli and blood is reduced. (3)
People with emphysema are described as "pink puffers". They are frequently cachexic (emaciated), with weight loss and muscle wasting due to their high breathing work. They are severely dyspnoeic (breath less), which is aggravated by any exertion. Chests are rounded or barrel shaped, due to hyperinflation of the lungs. The work of breathing makes these patients flushed and warm. (15)
Hyperinflation due to air trapping reduces inspiratory capacity (the volume of air able to be inhaled) and increases functional residual capacity (the air remaining in the lungs following a normal exhalation). This impairs respiratory muscle function, further contributing to respiratory distress. Hyperinflation occurs early in the development of COPD and is thought to be the main cause of dyspnoea on exertion--a symptom that is not easily correlated to the other measure of COPD severity--forced expiratory volume over one second (FEV1). (3)
Forced expiratory volume over one second
FEV1 and the ratio of FEV1 to the capacity of the lungs (forced vital capacity or FVC) are common measures of COPD severity. These are assessed through spirometry and are used to classify severity of airflow obstruction in COPD: (3)
* GOLD 1--mild--FEV1 [greater than or equal to] 80 per cent of predicted value (related to age, height, sex, and race).
* GOLD 2--moderate--FEV1 <80 per cent but [greater than or equal to] 50 per cent predicted.
* GOLD 3--severe--FEV1 <50 per cent but [greater than or equal to] 30 per cent predicted.
* GOLD 4--very severe--FEV1 <30 per cent predicted.
GOLD categories relate to risk of exacerbation, hospitalisation and death. These categories, however, do not relate to symptoms or degree of impairment in quality of life for patients with COPD, which should be assessed separately. (3)
Airflow obstruction, as measured by FEV1, is mainly due to small airway narrowing, but chronic bronchitis also plays a significant role.
Chronic bronchitis is defined as the presence of a chronic, productive cough for three months or longer, over two consecutive years, in the absence of other causes for the cough. (1) Mucus produced can be either clear or purulent and there may be a degree of bronchoconstriction that is alleviated by use of bronchodilators.
Bronchitis is caused by inflammation of the larger airways, in response to inhaled pollutants (including tobacco smoke) or repeated infections. Chronic inflammation causes thickening of the epithelium, influx of immune cells into the airways and increased mucus production. Damage to the epithelium causes loss of cilia, so that less mucus is trafficked up the airways and expectorated but instead pools in the lungs, increasing the risk of further infection and obstruction.
People with chronic bronchitis may be called "blue bloaters". They look hypoxic, with central cyanosis. In contrast to people with emphysema, they do not lose weight. As the disease progresses, heart failure occurs, leading to peripheral oedema (bloating).
Patients with significant chronic bronchitis are more prone to exacerbations and lower respiratory tract infections, and have a higher mortality rate. (15) Most patients with COPD exist on a continuum between bronchitis and emphysema. The mix of conditions determines gas exchange abnormalities, exercise tolerance and management strategies.
GAS EXCHANGE ABNORMALITIES IN COPD
Gas exchange is impaired as airflow obstruction and alveolar destruction worsen, leading to various degrees of hypoxaemia and hypercapnia. There are several underlying mechanisms involved. Patients with predominantly emphysema have relatively normal arterial blood gas (ABG) readings until late in the disease. Those with bronchitis suffer from hypoxaemia early on in the disease, and progress to hypercapnia as their COPD worsens.
Low oxygen in arterial blood (hypoxaemia) arises due to a mismatch between the air flowing into and out of the lungs and blood flow through the pulmonary capillaries. This is known as ventilation/perfusion (V/Q) mismatch. In chronic bronchitis, obstruction of the airways causes poor lung ventilation, but, unlike emphysema, the pulmonary capillaries are normal. This V/Q mismatch triggers responses that reduce ventilation and increase cardiac output, actually worsening the hypoxaemia. Red blood cell production increases (polycythaemia), increasing the viscosity of the blood, although advanced COPD is often associated with anaemia, worsening oxygen delivery to the tissues. (1,16)
[FIGURE 1 OMITTED]
For people with emphysema, the opposite V/Q mismatch occurs: pulmonary capillaries are destroyed along with the alveoli, leading to poor blood flow through the lungs. In response, cardiac output to the lungs is reduced and ventilation increased. Blood is relatively well oxygenated, but because of the low cardiac output, the tissues do not receive adequate oxygen and become hypoxic. (1)
Carbon dioxide (C[O.sub.2]) diffuses rapidly from the blood to the air in the lungs. Air in the alveoli of healthy lungs has less C[O.sub.2] than the blood, so C[O.sub.2] can diffuse into the alveoli and be excreted through exhalation. As long as there is fresh air moving in and out of the lungs, C[O.sub.2] will not accumulate. Where air flow is obstructed, C[O.sub.2] in the alveoli rises, and the gradient for diffusion is obliterated. C[O.sub.2] then accumulates in the blood, causing hypercapnia and respiratory acidosis.
Some people with COPD cannot be administered high doses of oxygen. For this group of patients, administration of oxygen above 24-26 per cent causes hypercapnia that can trigger respiratory failure and death. This phenomenon is generally explained as loss of hypoxic drive. With chronic hypercapnia, the normal drive to breathe (ie rising C[O.sub.2] levels in the blood) is blunted or lost. These patients therefore rely on low blood-oxygen levels to drive their respiratory effort. By giving them oxygen, the drive to breath is gone, and respiratory failure ensues. In fact, the physiological triggers involved are poorly understood. It is vital that carers of this subgroup of COPD patients understand that oxygen therapy is risky and should only be administered on prescription. Identification of these "C[O.sub.2] retainers" is only possible through ABG analysis.
A number of conditions are associated with COPD. Some arise directly from the pathophysiology of COPD, while others are not so obviously connected. Increasingly, the chronic inflammatory origins of COPD are being linked to other inflammatory conditions in the body, such as ischaemic heart disease, and the metabolic syndrome and diabetes. (17)
Pulmonary hypertension and heart failure
Where COPD causes hypoxaemia, there are serious cardiovascular consequences. Poor ventilation of regions of the lungs triggers vasoconstriction in those regions. If the area of poor ventilation is large, vasoconstriction can severely restrict blood flow, raising the pressure in the pulmonary arteries. Pulmonary hypertension also occurs where pulmonary capillaries are damaged by emphysema or inflammatory thickening of the blood vessel walls (which may be further aggravated by tobacco smoke). (18)
Pulmonary hypertension, polycythaemia and increased cardiac workload, due to hypoxaemia, strain the heart, causing heart failure in advanced COPD. Heart failure may also be due to the same risk factors which cause COPD. About 30 per cent of people with COPD have heart failure, (3) and it is important to be able to distinguish between worsening heart failure and exacerbation of COPD.
Right-sided heart failure impairs venous return from the systemic circulation. This raises venous pressure, causing oedema to develop in the extremities.
Left-sided heart failure impairs venous return from the pulmonary circuit, causing pulmonary oedema and worsened gas exchange. Hypoxaemia is increased and cardiac output is reduced.
Osteoporosis occurs frequently with COPD, especially in emphysema and, unusually, in males. While risk factors such as smoking, prolonged use of steroids, and low body weight contribute to the risk of osteoporosis in COPD, this does not account for all the incidence. At least part of the risk may be due to underlying chronic systemic inflammation. Whatever the underlying cause, routine screening and appropriate management for osteoporosis are essential to limit associated morbidity. (17)
Anxiety and depression
Depression and anxiety are more common in people with COPD than in the general population, or in those with other chronic diseases. The chance of being diagnosed with depression or anxiety within 12 months of diagnosis of COPD is doubled, with more frequent diagnoses in women and younger patients. Clinical outcomes are worse for this group, including hospital readmissions, economic burden and reduced self-management.
Lung cancer is the most common cause of death in patients with mild COPD. While smoking and ETS exposure are risk factors for both lung cancer and COPD, cancer rates are higher in smokers with COPD than in smokers with no respiratory disease. The underlying mechanisms of COPD development--chronic inflammation, oxidative stress and cellular proliferation--may contribute to cancer risk, or the diseases may be due to similar genetic susceptibility. (19)
There is no cure for COPD. Management rests on controlling symptoms, preventing and treating exacerbations, increasing exercise tolerance and delaying the progression of the disease. No existing therapies have an impact on long-term deterioration in lung function. (3) Therapy must be based on individual assessment (taking into account co-morbidities) and treatment goals developed with the patient.
Non-pharmacological management includes smoking cessation, daily physical activity and pulmonary rehabilitation, which improves exercise tolerance and reduces dyspnoea. Annual influenza vaccination is recommended and nutritional support should also be offered.
Choice of medications depends on the individual's condition and their responses. Bronchodilators (short or long-acting), such as beta-2 agonists and anticholinergics, reduce hyperinflation and increase exercise tolerance. Their effects may not be seen on lung tests, but subjective improvement is frequently reported.
Inhaled corticosteroids help patients with moderate to severe COPD, improving symptoms and quality of life, and reducing exacerbations. Oral corticosteroids should be reserved for management of exacerbations. (3) Roflumilast is an anti-inflammatory inhaled medication that may be effective in both stable COPD and during exacerbations, when given with a long-acting bronchodilator. It has a number of adverse effects.
The use of mucolytics, antitussives and inhaled nitric oxide (as a vasodilator) are not recommended under current guidelines. (3) Oral or intravenous opioids can be used to manage dyspnoea in severe and end-stage COPD, but these are not effective in all cases.
Long-term oxygen therapy for >15 hours per day is effective for patients with severe disease, who have ongoing, severe resting hypoxaemia. (3) All medications have adverse effects that may make them unsuitable for patients with co-morbidities. Toxicity can also occur, so education about correct administration and dosage is essential. The effectiveness of treatment needs be to assessed regularly: impact on dyspnoea, sleep, and activity levels should be evaluated, as well as adverse effects and overall satisfaction with the management regime.
An exacerbation of COPD is a period of acute worsening of respiratory symptoms, distinct from progression of the underlying condition and from acute lung infections such as pneumonia. Onset is abrupt, occurring over hours or a few days, and symptoms often appear before respiratory deterioration. Symptoms may include cough, increased sputum, wheeze or increased shortness of breath. There may also be fever, fatigue and loss of appetite. (10)
Exacerbations can: (3)
* Reduce quality of life.
* Prolong recovery time.
* Accelerate progression of the disease.
* Significantly raise hospitalisation rates and mortality (23-80 per cent).
Exacerbations may be caused by upper respiratory tract infections, spikes in air pollution, or failure to adhere to medication regimes. For one-third of exacerbations however, the cause is not identifiable. (3)
Treatment of mild to moderate exacerbations includes oxygen therapy (with serial ABG analyses), bronchodilators, oral or intravenous corticosteroids, and antibiotics if bacterial infection is identified. Fluid and nutritional intake must be monitored, and anti-embolic therapy is usually instituted. Non-invasive mechanical ventilation may be considered. (3)
Intensive care should be considered where the patient does not respond to initial emergency therapy, changes in mental status (confusion, lethargy, coma) occur, or there is persistent or worsening hypoxaemia or respiratory acidosis. (3)
Prevention and smoking cessation
Smoking cessation has the greatest impact of any management strategy on long-term outcomes for people with COPD. Intensive cessation programmes can attain 25 per cent long-term quit rates. (3) Nicotine replacement therapies, used correctly, have significant effect, as do oral medications, but all must be used in conjunction with support programmes. (3) Even brief interventions delivered by health professionals show more success than self-initiated strategies, although there is a direct relationship between counselling intensity and success. (3)
As more research demonstrates the effects of preconception, prenatal and perinatal exposures to cigarette smoke on lung development, the role of nurses in protecting the respiratory health of future generations through education and counselling becomes increasingly important.
Education and the role of primary care
It is vital that people with COPD are educated about their condition: its causes and risk factors for disease progression; the nature of the disease and expected progression; signs and symptoms of exacerbations and when to seek help. (3) The more patients, and their families, know about COPD, the more they can self-manage and retain control of care decisions relevant to their life circumstances.
People with COPD are likely to be high consumers of health services, and there is a significant role for specialist nurses in this field. (20) Specialist nurses in the community can: (3)
* provide ongoing monitoring to ensure treatment goals are being met;
* evaluate and reduce risk factors;
* monitor disease progression and co-morbidities;
* assess treatment regimes for effectiveness and adverse effects;
* develop individualised action plans for exacerbations;
* co-ordinate with other community agencies, such as physiotherapists, pulmonary rehabilitation programmes, smoking cessation groups and dietitians;
* provide in-home nursing care for exacerbations; and
* coordinate with hospital services during admissions and after discharge.
The high, and increasing, cost--both economic and social--of COPD suggests more health resources should be directed to prevention and community management of this chronic disease. Nurses have a key role in this, ensuring people with COPD receive optimum care and are fully informed in ways that allow self-determination in care.
After reading this article and completing the online learning activities, you should be able to:
* Discuss the causes of, and risk factors for COPD.
* Outline current understanding of the pathophysiology mechanisms.
* Describe strategies for managing chronic and acute COPD.
* Discuss strategies over the lifespan to reduce risk of developing COPD.
* References for this article can be found at www.cpd4nurses.co.nz.
Georgina Casey, RN, BSc, PGDipSci, MPhil (nursing), is the director of CPD4nurses.co.nz. She has an extensive background in nursing education and clinical experience in a wide variety of practice settings.
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|Title Annotation:||CPD + nurses; chronic obstructive pulmonary disease|
|Publication:||Kai Tiaki: Nursing New Zealand|
|Article Type:||Disease/Disorder overview|
|Date:||Jun 1, 2016|
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