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Understanding chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease is a major cause of worldwide chronic morbidity and mortality, and affects nearly three million people in the UK alone. Helen Lewis takes a look at this preventable and treatable condition and its management in primary care

Helen Lewis
RN BSc(Hons)
BMid(Hons)
Practice Nurse
Brynderwen Surgery
St Mellons
Cardiff

The Global Initiative for Chronic Obstructive Lung Disease (GOLD) has defined COPD as follows:
"Chronic obstructive pulmonary disease (COPD) is a preventable and treatable disease with some significant extrapulmonary effects that may contribute to the severity in individual patients. Its pulmonary component is characterised by airflow limitations that is not fully reversible. The airflow limitation is usually progressive and associated with an abnormal inflammatory response of the lung to noxious particles or gases."1

A decrease in maximal expiratory flow rates is the cardinal physiological abnormality associated with COPD. The condition's pulmonary component is characterised by airflow limitation, which is not fully reversible and results in a loss of lung function. 

Aetiology of the lung
The lungs are two cone-shaped organs in the thoracic cavity. They are separated from each other by the heart and other structures in the mediastinum, which divides the thoracic cavity into two anatomically distinct chambers. As a result, if trauma causes one lung to collapse, the other may remain expanded. The pleural membrane is a double layer that covers and protects each lung – the parietal pleura is the superficial layer that lines the wall of the thoracic cavity while the visceral pleura cover the lungs themselves.

Each lung is surrounded by its own pleural cavity, which means that if one lung is affected by inflammation – as in the case of pleurisy – it does not affect the other side. The lungs extend from the diaphragm to just slightly superior to the clavicles, and lie against the ribs anteriorly and posteriorly. The broad inferior portion of the lung is concave and fits over the convex area of the diaphragm. The apex of the lung is the narrow superior portion of the lung. To allow space for the heart, the left lung contains a concavity named the cardiac notch. Due to this space occupied by the heart and its related vessels, the left lung is 10% smaller than the right. Although the right lung is thicker and broader, it is space for the liver, which lies inferior to it.

It is estimated that the lungs contain approximately 300 m of alveoli, providing an immense surface area of 70 m2 (750 ft2) for the exchange of gases. Type II alveolar cells, which are rounded or cuboidal epithelial cells whose free surfaces contains microvilli, secrete alveolar fluid, which keeps the surface between the cells and the air moist. Included in this fluid is surfactant – a complex mixture of phospholipids and lipoproteins that lowers the surface tension of the alveolar fluid, thus preventing the alveolar from collapsing.2

Definition of COPD
The GOLD definition provides a better understanding of the complex, largely invisible process forming the natural history of COPD. The condition was formally dubbed the "Cinderella respiratory disorder" due to the lack of management and intervention it was afforded before 1997, when the British Thoracic Society (BTS) COPD guidelines were disseminated among GPs and practice nurses.3

Since 1997, research and considerable interest in COPD have started to emerge, but the definition, understanding and management of the condition are still developing. For clinicians who are new to the management of patients with COPD, explanation of the predominant physiological abnormality and the pathological processes involved (see Figure 1) may go some way towards a better understanding of the condition.

[[Fig 1 COPD]]

It could be argued that the working definition does not specifically target the smoking-related condition practice nurses are treating, as it encompasses other long-term respiratory conditions, such as emphysema, small airways disease and chronic bronchitis. However, with advances in our understanding of the pathophysiological diversity of this condition, a revised COPD-specific definition will undoubtedly emerge.

Epidemiology
COPD is a multicomponent disease with inflammation at its core. It is a major cause of morbidity and mortality. Smoking has been identified as the single greatest cause of an individual developing COPD. and is responsible for over 95% of all cases in the developed world.4 As practice nurses know, not all patients smoke conventional cigarettes, so it is worth remembering that 25 g of tobacco is equal to 50 cigarettes. A significant smoking load is usually around 20 pack years; however, it is true to say that, as with all other chronic diseases, the approach must be patient-centred so that compliance and successful management are achieved and sustained.

The NICE guidance stresses that encouraging patients with COPD (and arguably, all patients who smoke) to stop smoking is a fundamental component of their management and, of course, will benefit their health.3 All COPD patients who are finding it difficult to give up smoking should be offered counselling and help at every opportunity by clinicians.

While smoking is regarded as one of the most significant risk factors for developing COPD, it is acknowledged that the condition can also occur in nonsmokers. Lung function declines in healthy nonsmokers after the age of 35, at a rate of 25–30 ml per annum in FEV1. In at-risk smokers, the rate of decline may be double that – at about 50–60 ml per year.5 In general terms, factors are divided into two categories: host and environmental (see Box 1).  

[[Box 1 COPD]]

Although smoking is an accepted risk factor for developing COPD, low birth weight is unlikely to be at the top of a clinician's agenda when arriving at a diagnosis. However, this, in addition to childhood nutrition, may play a role in the development of the disease. Low birth weight babies are at an increased risk of developing COPD later in life and the reasons for this are not fully understood. However, a possible theory is the size and the development of the lungs and bronchioles during childhood, as well as the underlying reason for low birth weight in the first place. Not all infants of low birth weight are premature, but babies born very prematurely do not have fully developed lungs and the liquid surfactant that prevents the alveolar from collapsing by reducing the surface tension around the structures may also be a factor later on in life.

Lack of antioxidants within the diet has been suggested as a factor in the development of COPD, suggesting that an oxidant–antioxidant imbalance may be the cause of tissue inflammation and damage. Diets rich in fish oils and fresh fruit and vegetables help the body to balance the oxidant–antioxidant imbalance in part, so it is helpful for clinicians to stress the importance of a balanced diet to help prevent the onset of the disease.6

The Black Report, commissioned in 1977 by the Labour government, looked at a number of divisions in health, including the effect of social class on mortality.7 The report concluded that the lower down the social scale an individual, the greater the likelihood that they or their offspring would die at a younger age. COPD is associated with poverty, with individuals in the lower socioeconomic groups experiencing poor diet, damp housing and more frequent chest infections, and a greater number of individuals smoking in this group than any other. It is clear that the combination of these factors worsens not only the health of an adult but also the health and wellbeing of their children.

Microscopic and macroscopic characteristics present themselves in COPD. Consistent exposure to cigarette smoke in a susceptible individual will trigger an inflammatory reaction within the airways, which, ultimately, will cause irreversible damage to the connective tissue of the lung. Unlike asthma, with each exacerbation a degree of lung function is lost permanently. The symptoms of COPD cannot be identified as one disease, but a combination of four main diseases; namely, chronic asthma that has been relatively unresponsive to treatment; chronic bronchitis; small airways disease; and emphysema. The Venn diagram (Figure 2) shows how the interaction of these components leads to a diagnosis of COPD.8

[[Fig 2 COPD]]

Assessment of COPD
Signs and symptoms
Patients will often present to the GP when their lung function has been considerably reduced, usually with a FEV1 of 50% may have no abnormal signs, making diagnosis very difficult.

As the disease progresses, patients will become increasingly breathless and unable to carry out simple everyday tasks, such as washing, dressing and minimal exertion. Dyspnoea results from hyperinflation secondary to small airway narrowing and airway closure as a result of emphysema. The effect on an individual's lifestyle is one of complete devastation, resulting in not only physical suffering, but also mental health issues and social isolation. As Figure 3 shows, COPD that is not managed properly will lead to a poor quality of life, not only for patients but also for their families.

[[Fig 3 COPD]]

Cough and sputum production are a common symptom, but these can also be found in smokers in the absence of airflow limitation. Wheezing may be a presenting factor during exacerbations and periods of breathlessness. Ankle oedema and central cyanosis may also become noticeable in patients with pulmonary heart disease as a result of hypertrophy and right ventricular failure. In patients presenting with severe COPD, the effort needed to walk into the consulting room and undress may be enough to cause considerable distress. These patients may lean forward, rounding their shoulders and resting their arms on a table to ease their breathing. Their observed respiratory rate may be increased and they may use "pursed-lip" breathing.

It may be impossible for the patient to speak in complete sentences and exhalation may be prolonged. Inevitably, some patients will need to accept early retirement and the financial burden this brings to a household may cause significant strain on relationships. To a lesser degree, a diagnosis of COPD can lead to many activities being restricted as outlined below.

During this time, it is important for the clinician to be aware of problems an individual and their family may face with a diagnosis of COPD. It is vital to the successful management of these patients that holistic care is given in terms of addressing not only the condition, but also the patient's social and psychological needs.

As much exercise as possible should be encouraged. Undoubtedly, patients will be frightened by their diagnosis and reluctant to exercise, fearing an exacerbation. However, research suggests that a combination of strength and endurance exercise will improve quality of life for these patients over a sustained period of time.10 It is important for clinician to be aware of the patient's age and their physical capabilities, and goals set must be realistic, measurable and achievable.

Treatment must remain patient-focused throughout.
Remember, the majority of patients will only present when their symptoms have brought them to the door of the GP or practice nurse – it is not unusual for a FEV1 to be below 50% of predicted when they perform spirometry for the first time.

Diagnosis 
In the majority of cases, a diagnosis of COPD is arrived at after a thorough history and airflow obstruction on spirometry. Spirometry is essential in the diagnosis as it measures airflow and lung volumes. The FEV1 and the FVC are expressed in litre volumes and as a percentage of the predicted values.
Predicted values are dependent upon four components to assist in the diagnosis of COPD; namely:

  • Age.
  • Height.
  • Gender.
  • Ethnicity.

The ratio of FEV1 to FVC is expressed as a percentage. Values of less than 70% indicate an airflow obstruction. In restrictive lung diseases, both the FEV1 and the FVC will have a predicted value of below 80%; however, the ratio between the FEV1 and the FVC will be either normal or high.10 Box 2 gives a summary of the values for FEV1; FVC; and FEV1/FVC ratio in normal, obstructive and restrictive patients.

[[Box 2 COPD]]

Conclusion
COPD is currently the fifth leading cause of death in the UK. However, despite medical knowledge and advances in the management of this condition, mortality is expected to rise in the coming years. This is in stark contrast to the marked decrease in other chronic conditions such as heart disease and stroke. For the patient and his or her family, the burden of disease in terms of quality of life and health issues is
staggeringly high. Lifestyle changes, such as smoking cessation and exercise, should be encouraged at every opportunity.

Using patient-specific treatments to delay the progression of the condition, preventing exacerbations and reducing the risk of comorbidities will ease both the clinical and economic burden of the condition. Successful management involves the patient in their own care – holistic treatment is the way forward in chronic disease management and the clinician who is both knowledgeable and confident will ultimately achieve success in this once-thought-of Cinderella respiratory disease.

References
1. Global Initiative for Chronic Obstructive Lung Disease (GOLD). Global Strategy for Diagnosis, Management, and Prevention of COPD. Available from: http://www.goldcopd.org/Guidelineitem.asp?l1=2&l2=1&intId=2003
2. Tortora GJ, Grabowski SR. Principles of Anatomy and Physiology. USA: Wiley & Sons; 2003.
3. National Institute for Health and Clinical Excellence (NICE). Chronic obstructive pulmonary disease. Management of chronic obstructive pulmonary disease in adults in primary and secondary care. London: NICE; 2004.
4. Halpin DM, Miravitlles M. Chronic obstructive pulmonary disease: the disease and its burden to society. Proc Am Thorac Soc 2006;3(7):619–23.
5. Buist AS, Vollmer WM. Smoking and other risk factors. In: Murray JF, Nadel JA, eds. Textbook of Respiratory Medicine. Philadelphia: WB Saunders; 1997: 1259–87.
6. Grievink L, Smit HA, Ocke MC, van't Veer P, Kromhout D. Dietary intake of antioxidant (pro)-vitamins, respiratory symptoms and pulmonary function: the MORGEN study. Thorax 1998:53:166–171.
7. Department of Health (DH). Inequalities in Health: Report of a Research Working Group. DH, 1980. Available from: http://www.sochealth.co.uk/history/black.htm 
8. Bellamy D, Booker R. Chronic Obstructive Pulmonary Disease in Primary Care: all you need to know to manage COPD in your practice, 3rd edn. London: Class Health; 2004.
9. Russell REK, Ford PA, Barnes PJ. COPD: a guide to total patient care. Current Medicine Group; 2007.
10. Ortega F, Toral J, Cejudo P et al. Comparison of effects of strength and endurance training in patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2002;166:669–74.