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Week 2 Diagnosis and assessment

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VOL: 98, ISSUE: 36, PAGE NO: 27

JUDITH McALLISTER, MA,RN, Respiratory Specialist Nurse, North Peterborough Primary Care Trust; Regional Trainer, Asthma and COPD, National Respiratory Training Centre, Warwick

Sponsored by PFIZER

JUDITH McALLISTER, MA,RN, Respiratory Specialist Nurse, North Peterborough Primary Care Trust; Regional Trainer, Asthma and COPD, National Respiratory Training Centre, Warwick

Introduction

The presenting symptoms of chronic obstructive pulmonary disease (COPD) are common to a number of diseases. Nurses need to have an understanding of how the diagnosis is made and what tests should be carried out. Those who manage asthma in primary care need to be able to recognise when patients may have COPD rather than asthma, as the management for each differs. This Part focuses on the diagnostic process in COPD and the principal drugs used once the diagnosis has been made.

Symptoms

Most patients initially complain of shortness of breath on exertion, but there may also be a cough and wheeze. Patients who smoke may expect such symptoms. Ex-smokers may attribute their symptoms to the ageing process, particularly as symptoms often do not become noticeable until people are in their 50s and 60s, which may be up to 10 or 15 years after they have stopped smoking. COPD should be considered in patients who present to their general practitioner complaining of breathlessness which worsens on exertion, particularly where there is a significant smoking history or exposure to other risk factors.

An accurate history will suggest the diagnosis and tests will help to confirm it.

Key features to look for are suggested in Fig 1. Sudden onset is unlikely, although many patients relate the start of their symptoms to an episode of flu. However, careful questioning usually reveals some limitations in activity before this. Common differential diagnoses of breathlessness are listed in Fig 2.

Think Point: How much do you know about the conditions listed in Fig 2? What common cause links cardiac disease, cancer and COPD? You may wish to refresh your memory of the less common conditions.

Investigations

Confirmation of a diagnosis of COPD will be made following a chest X-ray, a full blood count, ECG/echocardiography and spirometry. Exclusion of the various alternative causes of breathlessness will confirm diagnosis. The number of investigations will depend to a great extent on the patient's history, but a chest X-ray and haemoglobin check are usual, and spirometry is vital for all patients. Any suggestion of cardiac disease in the history would suggest the need for cardiac investigations. Increased sputum production, particularly if purulent, may suggest bronchiectasis. O'Brien et al. (2000) found that 25% of the COPD patients they screened had evidence of bronchiectasis on a CT scan.

While chest X-ray cannot diagnose COPD, it is a useful screening tool to exclude other pathology such as lung cancer (BTS, 1997a). In most cases of mild to moderate COPD, the chest X-ray will be normal or reveal features of hyperinflation, which is not a sufficiently sensitive sign to confirm COPD.

A full blood count easily identifies anaemia and has the additional benefit of identifying polycythaemia. This is often found in more advanced disease, and is a compensatory mechanism to increase oxygen delivery to the tissues.

Unfortunately for many COPD patients, the disease is first identified during a hospital admission for a 'chest infection'.

Think Point: What investigations do COPD patients undergo in your area of work?

Spirometry

The most important investigation in COPD is the objective demonstration of irreversible airflow obstruction. Spirometry provides confirmation of an obstructed pattern of airflow and, if used in conjunction with a bronchodilator and steroid reversibility testing, can exclude a diagnosis of asthma. COPD cannot be confirmed until reversible disease (asthma) has been excluded. Peak flow measurements, although extremely useful in asthma, do not measure airflow through small airways, are effort-dependent and cannot distinguish between different patterns of airflow.

Patterns of airflow are determined by two measurements: forced expiratory volume in one second (FEV1), and forced vital capacity (FVC). These measurements are made by asking the patient to inhale to maximum capacity and blow out hard and fast until maximum expiration is reached. The amount of air expelled in the first second (FEV1) is measured and compared to how much air is expelled in total. These measurements are compared with normal predicted values for age, sex, height and ethnic group. If the FVC is normal but the FEV1 is less than normal, the ratio will be reduced to less than 70%, and this indicates obstruction. Examples of spirometry traces are shown in Fig 3.

Spirometry can easily be carried out in both primary and secondary care, provided the person carrying out the testing has access to reliable equipment and is adequately trained. The development of portable spirometers has moved simple lung function testing out of the laboratory and into respiratory wards, outpatient clinics and general practice. BTS guidelines for lung function testing (BTS and Association of Respiratory Technicians and Physiologists, 1994) should be adhered to in order to maintain the accuracy and reliability of the equipment and the results. In practice this means regular calibration checks on spirometers and obtaining a hard copy of the trace. Without a visual display of the 'blow' it is not possible to guarantee that the patient has performed an adequate test, and without adequate training nurses may not recognise a poor quality test.

Patients need to be adequately prepared for spirometry. If it is to be undertaken for diagnostic purposes, patients must be clinically stable (4-6 weeks post-exacerbation), and should have followed guidance given to them before the test (Fig 4) (BTS et al., 1994). The procedure needs to be explained and demonstrated to the patient, who must be encouraged to make the maximum effort when undergoing the test.

Think Point: What advice do you give to patients regarding preparation for spirometry? Do you provide written guidance? If you use a spirometer how is it maintained? Can you interpret the results?

Bronchodilator reversibility

If spirometry shows obstruction, reversibility testing should be carried out. High dose beta agonists are given and spirometry is repeated after 15 minutes. Anticholinergics should also be tried, as older patients may have a better response to these drugs (GPs in Asthma Group, 1998), waiting 30 minutes before rechecking the spirometry results. An increase in FEV1 of 200ml and 15% demonstrates reversibility above that expected by chance, while increases of 400ml or more suggest a significant asthma element. Failure to reverse to normal, or to achieve significant response, that is, >400ml, demonstrates irreversible airflow obstruction.

Steroid reversibility

All patients who have a positive response to bronchodilators and all those with moderate disease should have a trial of corticosteroids (BTS, 1997a). Around 10 - 20% of patients with COPD will show a significant improvement in FEV1 with steroids (Callahan et al., 1991). It is assumed that those who respond to oral steroids will benefit from inhaled steroids, although no evidence exists to support this. Current management guidelines advise inhaled steroids only for those who have a positive steroid trial (200ml + 15% improvement in FEV1) (BTS, 1997a; Pauwels et al. 2001). The latter report also recommends the use of inhaled steroids in those whose FEV1 is less than 50% of predicted and who have frequent exacerbations of their condition.

The steroid trial consists of giving 30-40mg of prednisolone in a once daily dose for a period of two weeks, with spirometry testing at the start and end of the trial. If oral steroids are contraindicated, six weeks of high dose inhaled steroid may be given, at a total daily dose of 1000mcg of beclomethasone dipropionate, 800mcg of budesonide or 500mcg of fluticasone propionate (BTS, 1997a). Problems arise when patients are already on inhaled steroids. A slow reduction in inhaled steroids is recommended, as an increased morality rate has been noted with their rapid withdrawal (Jarad et al., 1999). If a patient is able to stop inhaled steroids without difficulties, a steroid trial can then be carried out. A pragmatic approach to those already on inhaled steroids would be to stop withdrawal should an increase in symptoms and exacerbation rates occur and maintain the steroid dose at the level above that at which increased symptoms occurred.

Treatment

Only two interventions significantly alter disease progression in COPD: smoking cessation and the use of long-term oxygen therapy (Fletcher and Peto, 1977; Medical Research Council Working Party, 1981). Other interventions are palliative, aimed at controlling symptoms and minimising disability.

Bronchodilator treatments

Lack of improvement in terms of lung function does not mean that bronchodilators are useless in COPD. In fact they are the cornerstone of management, providing relief from breathlessness and an increase in exercise tolerance, possibly by reducing hyperinflation and allowing the lungs to work more efficiently. Trials of bronchodilator treatments should be undertaken, and response assessed in terms of improvements in disability and quality of life, which is far more meaningful to the patient than a change in his/her lung function. Assessment of disability can be as simple as asking the patient to rate his/her level of breathlessness on a visual analogue scale such as the oxygen cost diagram (Fig 5), or carrying out a formal assessment using a measurement of walking distance such as the six-minute walk or the incremental shuttle test (BTS, 1997a).

Short-acting beta 2 agonists are often used as a first-line treatment because of their rapid onset of action. They may initially be used before exercise, but as symptoms progress, regular doses may be preferred (Van Schayck et al., 1995). Anticholinergics may be more helpful in some patients (Leitch et al., 1978) while combinations may provide additional effects not found with either preparation alone (The Combivent Inhalation Aerosol Study, 1994). The use of long-acting beta 2 agonists in patients with negative bronchodilator reversibility has not been recommended by the British Thoracic Society (BTS, 1997a), but a study looking at the effectiveness of salmeterol in COPD (Mahler et al., 1999) found that this drug was as effective as ipratropium bromide, and a systematic review of four randomised controlled trials (Appleton et al., 2002) suggested improvements in quality of life and breathlessness when beta 2 agonists were used. Long-acting beta 2 agonists are recommended by the NHLBI/WHO Workshop Report guidelines (Pauwels et al., 2001) as being more convenient and as effective as short-acting beta 2 agonists. Oral beta 2 agonist preparations can be used but are not usually required.

Problems of inhaler technique are seldom insurmountable: the use of large and small spacing devices with metered dose inhalers allows easy use and requires less manual dexterity than nebuliser therapy. Drug side-effects increase as doses increase, and should be monitored. Inhaler therapy can provide an equivalent effect to oral preparations at a lower dose, with more rapid onset. The inhaled route should therefore be used wherever possible.

Theophylline and its derivatives can provide some benefit in COPD, mostly by improving respiratory muscle strength and effectiveness (Peake et al., 1988). However, their usefulness is limited by a narrow therapeutic range which requires regular checks of serum levels, and a high side-effect and interaction profile (Fig 6), consequently they are not recommended for patients with mild to moderate disease (BTS, 1997a).

Nebuliser therapy

For a few patients, nebulised therapy will give some benefit, but for most this is not required. Objective assessment of benefit should be made before nebulised therapy is recommended long term. High doses of bronchodilators may benefit some patients, and it may be convenient to deliver such doses by nebuliser (BTS, 1997a).

British Thoracic Society guidelines recommend that nebulisers should be supplied only to patients who have been assessed by a respiratory physician (BTS, 1997a), to ensure that the diagnosis is correct and that other treatment options have been fully evaluated. Responsibility for the maintenance and replacement of equipment lies with the person who supplied it. This creates difficulties for patients who purchase their own. British Thoracic Society guidelines (BTS, 1997b) recommend that every district hospital should have a centralised nebuliser service.

Think Point: Does your hospital or general practice loan nebulisers to patients? What arrangements exist for maintenance of this equipment?

Inhaled corticosteroids

Inflammation is present in the airways of patients with COPD, but it differs from asthmatic inflammation and does not seem to respond to inhaled corticosteroid therapy (Barnes, 2000). Four large trials have investigated the long-term effects of inhaled steroids in slowing the decline in lung function in COPD. No benefit has been found, despite small initial rises in lung function: rates of decline in FEV1 in both treatment and placebo groups remained the same (Vestbo et al., 1999; Pauwels et al., 1999; Burge et al., 2000; Lung Health Study Research Group, 2000). Clearly, then, inhaled steroids do not improve lung function, but one study, ISOLDE (Burge et al., 2000) reported a slowing in decline in quality of life and a reduction in exacerbation rates in the treatment group. Recommendations from the British Thoracic Society (1997a) regarding the use of inhaled steroids are based on what was known at that time.

The most effective dose of inhaled steroid in COPD is not known. Recommendations from the British Thoracic Society (BTS,1997a) suggest high doses, such as those used for trials of inhaled steroids. Oral steroids on a regular (daily basis) are not currently recommended, but some patients with severe disease report benefit. Risks of side-effects increase with increasing dose, so that even inhaled steroids cause side-effects at recommended doses. Use of spacer devices and mouth rinsing will reduce local side-effects, and should be recommended.

Think Point: Review the contraindications, side-effects and interactions of the drugs discussed in the section above on treatment.

Conclusion

COPD is diagnosed when irreversible airflow obstruction has been demonstrated by spirometry, and other causes of breathlessness have been excluded. Treatment aims to minimise symptoms and reduce disability: the cornerstone of treatment is inhaled bronchodilator therapy despite lack of effect on lung function. Not all patients benefit from inhaled steroids and these should not be used unless there is evidence of benefit, as the risk of side-effects is high.

Next week: Nursing care and implications for nursing

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