Copyright ©ERS Journals Ltd 2001 Modern treatment of chronic obstructive pulmonary diseaseDept of Medicine, University Hospital Aintree, Liverpool, UK CORRESPONDENCE: P.M.A. Calverley, University Hospital Aintree, Dept of Medicine, Longmoor Lane, Liverpool, L9 7AL, UK. Fax: 44 01515295888 Keywords: bronchodilator therapy, chronic obstructive pulmonary disease, inhaled corticosteroids, pulmonary rehabilitation, smoking cessation, treatment guidelines
Received: March 26, 2001
Chronic obstructive pulmonary disease (COPD) is a major cause of ill health and medical expenditure worldwide. Despite recent increases in the knowledge about the nature of the disease process and recognition of cytokine-mediated pathways of inflammation, current management is focussed on patient outcomes that relate to physiological measures of dysfunction. The new Global initiative in Obstructive Lung Disease (GOLD) management guidelines are evidence-based and stress both pharmacological and nonpharmacological therapy. Effective drug therapy can help smoking cessation in motivated patients (nicotine replacement, bupropion). Bronchodilator therapy is best given by inhaler, can use either beta-agonists or anticholinergics and is more effective if long acting. Health status and exercise performance can improve without parallel changes in forced expiratory volume in one second. Inhaled corticosteroids are indicated if there is a significant bronchodilator response or the patient has more severe disease with frequent exacerbations. Antioxidant therapy remains controversial but may reduce exacerbation number. Acute exacerbations require higher doses of bronchodilators and short courses of oral corticosteroids. New drug treatment is a major priority for chronic obstructive pulmonary disease research. Chronic obstructive pulmonary disease (COPD) is a major cause of mortality and morbidity worldwide. It is a common cause of hospitalization and days lost from work, but until recently has not attracted the kind of intensive research interest devoted to other forms of obstructive lung disease, particularly bronchial asthma. This situation has changed substantially in the last decade and it is now clear that a scientific basis is present for the majority of existing treatments. In most cases these have been "borrowed" from approaches used in managing bronchial asthma 1. The outcomes of treatment in COPD are very different and it is not appropriate to assess responsiveness in this condition by expecting changes of a similar magnitude to those seen in patients with asthma. Indeed, if they were present such patients would be considered asthmatic 2. Nonetheless, pharmacological treatment does have an important role to play in the management of these patients. The principal goals of which are summarized in table 1
In this article the major treatment approaches will be reviewed and the extent to which they produce improvements with individual patients will be considered. Before doing so it is worthwhile reviewing how pharmacological management is organized and what recommendations have been made to optimize COPD management.
Following the success in early 1990s of several national and international treatment guidelines for asthma a range of groups have developed treatment recommendations for the management of COPD. The European Respiratory Society led the way in this 3 but was subsequently followed by the American 4, British 5 and many other national bodies. All of these documents have been expert, consensus-based statements and none have tried to systematically evaluate different therapies in terms of the evidence available to support their use in COPD. In most cases an initial statement has been made but not revised and so much of the information available is now lagging behind with the rapid pace of developments in the pharmacological therapy of COPD. This has been partly addressed by the conclusion of the first stage of the Global initiative for Chronic Obstructive Lung Disease (GOLD). This programme has, as its name suggests, a global purpose and is supported by the World Health Organization (WHO) and the National Heart, Lung and Blood Institute in the USA. It has applied a standardized evidence-grading procedure to the available literature and has consulted widely to obtain the maximum amount of input to its treatment recommendations. It is likely that further revisions of the national and international societies documents will take place and preliminary discussions about the best way to achieve this and integrate this with the GOLD programme are now occurring. All of these expert reviews agree that the management of stable COPD involves several clear steps: 1) Reduction of risk factor exposure and particularly cigarette smoking; 2) optimizing expiratory flow by the use of bronchodilator drugs; 3) Reducing pulmonary inflammation most commonly attempted using corticosteroids; and 4) preventing and managing acute exacerbations of COPD. In addition there is strong evidence for the role of domiciliary oxygen treatment in patients with persistent hypoxaemia and of pulmonary rehabilitation as an added adjunctive therapy at all stages of the disease from the point when the patient develops exertional breathlessness. Surgical therapy has a role in more advanced disease or where there is a large localized bulla with compression of adjacent lung structures. Ventilatory support either acutely or chronically using noninvasive methodologies has been studied and the acute use of this therapy in patients with hypercapnia is now clearly justified 6. In this review, the potential mechanisms of action of pharmacological therapy and the evidence for their effectiveness will be considered.
Tobacco smoking is the best recognized factor producing COPD, as continued exposure to tobacco is associated with an accelerated decline in lung function with time 7. Conversely, there are now good data in early COPD that smoking cessation produces a small but statistically significant improvement in lung function and permits the forced expiratory volume in one second (FEV1) to decline at a more normal pace 8. To date, there is much less direct information about the effects of smoking cessation in people with more established disease i.e. <50% predicted FEV1. There is a strong belief that this remains an appropriate measure even if there is evidence of persisting inflammation in those patients who have successfully stopped smoking. The complexity of inhaled tobacco smoke makes it a difficult agent to study mechanistically and to date, no specific pattern of cytokines has been attributed to specific components of this complex mixture of gases and particles. In the foreseeable future, it is most unlikely that a "safer" cigarette will be developed and hence pharmacological therapy has largely been devoted to increasing the successful cessation rate rather than reducing the impact of this important causative agent. Until recently, most approaches to smoking cessation were behavioural and the success rate when measured objectively using exhaled carbon monoxide analysers has been disappointingly low. The recognition that cigarette smoking is specifically connected to nicotine addiction in the majority of cases, and that smoking withdrawal symptoms can be produced by providing nicotine, allowed the first pharmacological therapies to be developed. These comprised nicotine replacement treatments, which have been shown in a series of studies to be effective ways of increasing the sustained rate of quitting 9. Nicotine delivery does not mimic the rapid absorption characteristic of inhaled nicotine but instead provides a background level of this drug, which diminishes some of the unpleasant effects associated with its cessation. Which preparation is used is as much determined by cultural norms as by the specifics of absorption. In North America, nicotine chewing gum has proven to be highly successful but this is less appropriate in European Societies were nicotine patches or nasal sprays are preferred. The most important pharmacological development has been the chance observation that the antidepressant drug bupropion was associated with an unexpectedly high incidence of smoking cessation in patients who used this treatment whilst they were depressed. This has subsequently led to a successful research programme, which has demonstrated that this drugs properties as a dopamine antagonist within the central nervous system seem to reduce the degree of nicotine dependence. At the moment it has only been studied in populations of people who are motivated to quit and although several large studies have been presented as abstract, only two investigations in such motivated "patients" have been reported in detail 10. These clearly show that this agent is at least equivalent to nicotine replacement and possibly superior in the short term. It increases the smoking cessation rate and also has an additive effect with nicotine replacement. Although the one-year quit rate of approximately one third of patients might appear to be disappointing, it represents a substantial advance on any previous smoking cessation strategy. This drug is now licensed in North America and Europe and is likely to play an important role in patients with COPD although specific studies examining the smoking cessation behaviour in these patients have not yet been presented. A major side effect is insomnia, which can be limiting in some patients. Epilepsy was originally reported when used in populations of patients with significant depression but has not been an important finding in patients attending smoking cessation programmes. Future development of related agents is likely. Suitability for support programmes, nicotine replacement and bupropion is dependent on the willingness of the patient to contemplate changing their smoking habit, something which a diagnosis of COPD can often promote. Additionally, patients who are less physically dependent on nicotine i.e. those who do not smoke until after getting out of bed in the morning are more likely to succeed in any form of smoking cessation intervention. There are some data suggesting that higher doses of nicotine replacement may be more effective in these particularly dependent individuals and an approximate assessment of the degree of dependence, based on the time to first cigarette, is a useful agent to using these therapies.
Bronchodilator drugs remain the most widely used and effective way of controlling symptoms in COPD. Their major effects are summarized in table 1 In the last ten years there has been clear evidence that the functional benefits of inhaled bronchodilator treatment are not closely related to the changes in FEV1 they produce. Thus, patients who meet conventional criteria for having a bronchodilator response fair no better than those who are "unresponsive" when assessed in terms of self paced walking distance, resting or end exercise breathlessness. Improvements occur after inhaling an active drug compared to a placebo irrespective of the spirometric change 15, 16. There is now clear evidence that the improvements in breathlessness produced by any class of inhaled bronchodilators are due to a reduced tendency to develop dynamic hyperinflation during exercise 17, 18. It is likely, but not certain that similar processes explain the reduced work of breathing previously reported in patients receiving oral theophyllines 19. Predicting the magnitude of these changes is difficult from resting measurements and surprisingly little is known about the individual reproducibility of this form of response. The best clinical strategy is to enquire whether the patient experiences subjective benefits, as this is likely to be a better reflector of the true respiratory physiology than simply measuring forced expiratory flows. Until recently, inhaled bronchodilators had a relatively short duration of action with ipratropium being somewhat longer than the beta-agonists, a finding which suggested that three times daily use was adequate. This has been based more on statistical rather than clinical considerations and it seems likely that most short-acting beta-agonists have their optimum effect in the 4 h after administration, with their effects measurable from around 30 min onwards. Oral agents such as the theophylline compounds clearly can be dosed over longer periods, particularly with the availability of slow release preparations. However, the unpleasant side effects, particularly those associated with phosphodiesterase (PDE) III inhibition such as the ventricular arrythmias have now made this therapy a third line option. Long-acting inhaled beta-2 agonists have now been shown to be effective in terms of increasing FEV1 for around 12 h after a single dose 1. This effect is sustained over weeks of treatment and unlike previous reports of short-acting bronchodilators, is associated with a clinically significant improvement in health status 20. These findings have been established using salmeterol but currently unpublished studies with formoterol confirm these results in a wider range of subjects. There seems to be no advantage in giving higher doses of long-acting beta agonists presumably because of tremor and sleep disturbance. Four-times daily ipratropium produced a similar improvement in health status to twice daily salmeterol in one study, but this has not been confirmed using a different questionnaire in a larger investigation. There is some tantalizing evidence that the time between exacerbations can be increased by using long-acting inhaled beta-agonists 21. Although further prospective studies are required to establish this definitely. The development of once daily therapy with tiotropium bromide represents a further advance. This is an exceptionally long-acting inhaled anticholinergic drug which produces significant improvements in pulmonary function over three months compared with placebo and ipratropium 22. Data in abstracts suggest that this also improves health status and there are clear questions to be answered about its relationship with the long-acting inhaled beta-agonists and with a further combination therapy will be the optimum way of providing maintenance bronchodilitation. There still seems to be a role for short-acting bronchodilator treatment to help with acute symptoms and high doses are often administered by wet nebulizer to patients with severe end-stage disease. The evidence that this is more beneficial than lower doses for a spacer device is limited and almost certainly requires a more detailed physiological approach than that currently used in the literature.
The recognition of COPD is characterized by persistent airway inflammation and that as the disease advances there are an increased number of neutrophils in the alveolar structures which makes anti-inflammatory therapy both a logical and attractive approach to managing this condition. In practice this has meant using either oral or inhaled corticosteroids, and data about other forms of intervention has not, so far, extended to man. The experimental evidence in support of corticosteroid therapy in COPD, as opposed to asthma, is conflicting. Some studies report reductions in neutrophil chemotaxis and reduced numbers in induced sputum 23, 24 while others using a variety of oral and inhaled interventions have found no effect on important sputum markers such as interleukin-8 and tumour necrosis factor- 25. Unpublished biopsy data suggests there may be a small reduction in the number of mast cells in airway biopsies from COPD patients treated with inhaled corticosteroids but overall the pattern of other inflammatory markers, and in particular T-lymphocytes, is unaffected. Empirical observations initially suggested a survival benefit for patients treated with inhaled corticosteroids 26 and early reports pointed to a substantial improvement in patients managed this way compared with those treated with bronchodilators alone 27. However, these data included large numbers of people who would in other circumstances be classified as having bronchial asthma. Data studying the change in FEV1 over time was again initially encouraging with a significant improvement in prebronchodilator FEV1 28 a finding confirmed on a subsequent meta-analysis of European studies 29. Subsequent prospective investigations have used a number of inhaled corticosteroids as this route was preferred to oral therapy due to the high incidence of side-effects and evidence for corticosteroid myopathy which may contribute to mortality 30.
Four studies are now available which have addressed the role of inhaled corticosteroids in the long-term management of COPD. Each has studied rather different groups of patients and their baseline characteristics are summarized in table 2
In the three studies where it was reported, skin bruising occurred in 5% of individuals treated with the active drug. There were no clinically significant differences in serum cortisol measurement and data about bone mineral density is conflicting, with the studies using budesonide finding no ill effects but the Lung Health Study using triamcinolone suggesting some deterioration in femoral neck bone density with time. Local side effects such as oral candidiasis and hoarse voice occurred with a frequency similar to that seen in bronchial asthma.
Current guidance incorporated in the GOLD report suggest that inhaled corticosteroids should be considered in patients with an FEV1 <50% pred who have at least one exacerbation per year. Additionally, there are data suggesting that
COPD is characterized by periodic worsening of the symptoms sustained for more than 48 h commonly described as an exacerbation. This can occur at all stages of the disease and vary from a troublesome increase in cough and sputum production to severe breathlessness and respiratory failure. The therapy offered is dictated by the severity of the symptoms and the background severity of the COPD but falls broadly under four headings.
Treatment of the precipitating factor
Increased bronchodilator therapy
Anti-inflammatory therapy
Other medications Intravenous aminophylline is frequently used in the management of acute COPD although there are no good clinical trials to demonstrate its benefit in patients who have received adequate doses of nebulized bronchodilators. It can accentuate the toxicity in patients who are already receiving oral therapy and should be used with caution, ideally with the availability of plasma theophylline levels. Respiratory failure can be managed by giving parental respiratory stimulants with doxapram hydrochloride being the favourite drug. Reports over 30 years ago suggest that this might improve blood gas tensions, but more recent studies have found it inferior to noninvasive positive pressure ventilation in the management of significant hypercapnic exacerbations of COPD 41.
There is now substantial evidence that through good clinical practice in the management of chronic obstructive pulmonary disease patients it is possible to lessen the symptoms and intervene positively for these patients. Further progress will be dependent on the ability to understand and categorize the processes which underline chronic obstructive pulmonary disease both in terms of its progression and the patients symptoms. As this knowledge accumulates more rational therapy will be possible. Until then, the steps outlined in table 2
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