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Asthma: a changing perspective on management
CurrentAnaesthesia and Critical Care (1996) 7, 260-265
© 1996 PearsonProfessionalLtd
Medicine
Asthma: a changing perspective on management
R T. F l o o d - p a g e and M. R. Partridge
In understanding the role of environmental factors in the pathogenesis of asthma, it is important to make the distinction between causes of asthma and exacerbants (which worsen existing asthma). Agents causing asthma are thought to sensitize the bronchial mucosa so that subsequent exposure to agents which exacerbate asthma may result in the mucosal inflammation and bronchial wall constriction characteristic of the disease.
Asthma is a common condition. It is estimated to affect around 5% of adults in the UK and between 10% and 15% of children. In addition, 4% of adults and 6% of children are estimated to have asthma of severity sufficient to require regular medical supervision.1 It has significant socio-economic importance; 11 million working days each year are lost because of asthma, costing an estimated £550 million in lost productivity. Its cost to the health services is estimated at £450 million. In the UK the estimated number of hospital deaths and discharges due to asthma doubled between 1979 and 1985. The number of prescriptions for asthma has doubled over the same period. ~ The reasons for the increasing burden from this disease are not clear.
Timing of exposure Sensitization in utero and in infancy
There has been a lot of recent interest concerning when in an individual's life sensitization occurs. One Scandinavian study showed that birch pollen allergy in children occurs more frequently in those born just before the pollen season. 5 Another study compared the development of skin prick allergy to dog hair in households with a dog throughout pregnancy, with those introducing a dog later, or with no dog at all. The likelihood of developing allergy appeared to be greatest from the second trimester of pregnancy until the end of the first year. Similarly, increased house-dust mite exposure during the first two years of life appears to be associated with an increased skin prick response and increase in asthma prevalence in adolescence. 6
T h e i m p o r t a n c e o f the e n v i r o n m e n t
Even allowing for differences in diagnostic fashion and in methods of detection, asthma prevalence has doubled over the last 2-3 decades. 2 Our genetic make-up could not have changed over this time and for this reason there is general agreement that while genetics plays a significant role in determining who is at risk of developing allergic disease, changes in our environment are more likely to explain the increase in prevalence. This seems to be borne out by a series of studies demonstrating a markedly higher prevalence of asthma in the offspring of migrants to urban areas when compared to the offspring of those who remained in their rural community of origin. 3'4
Possible initiating agents Atmospheric pollution
One area which attracts debate is the importance of air pollution in urban areas, principally oxides of nitrogen, ozone, sulphur dioxide and particulate matter. The migration studies previously discussed would suggest that pollution might be important but urbanization is also
Dr Patrick T. Flood-page MB MRCP madDr Martyn R. Partridge MD FRCP, Chest Clinic,Whipps Cross Hospital,LondonE11 1NR, UK. Correspondenceto Dr M. R. Partridge.
260
ASTHMA 261 associated with changes in diet, changes in housing and smoking habits. A study of the prevalence of asthma in rural and urban areas of Scotland, where confounding factors such as housing and diet are more likely to be constant, showed no differences] Whilst studies have clearly shown that air pollutants can both provoke acute airways narrowing and can enhance the sensitivity of airways to other allergens, 8"9no study has convincingly demonstrated an association between the severity of pollution and the causation of asthma. Moreover, as asthma has been increasing in the past 30 years, pollution levels have not significantly increased.
Plant aeroallergens Pollen and other plant-derived airborne particles have long been recognized as triggers of asthma. Birch pollen has been implicated in neonatal sensitization and raised pollen counts have been connected with seasonal peaks in asthma exacerbations and most recently with thunderstorm-related asthma epidemics. ~° Although important as a cause of asthma exacerbations in susceptible individuals, pollen is unlikely to explain the recent increase in prevalence of asthma.
Tobacco smoking Smoking significantly increases the risk of asthma in the offspring of women who smoke during pregnancy and in children exposed to cigarette smoke in the home. This effect is lost as the child gets older and by the age of fifteen there is no significant association. Smoking in adulthood may exacerbate pre-existing asthma, and for certain agents the incidence of occupational asthma is higher amongst smokers, but in other situations smoking has not been shown to predispose to the development of asthma.
Diet Over the last 40 years diet in the western world has changed considerably. In the UK, the population now consumes 50% less fresh vegetables, 30% less fruit and proportionally more processed food. The first change that accompanies urbanization in developing countries is this change in diet towards processed food. It is conceivable that this is connected to the increase in asthma and may reflect an increased susceptibility to develop asthma consequent upon altered dietary antioxidant levels, u
Respiratory virus infections Recent research using PCR (polymerase chain reaction) techniques detected evidence of viral infection in 73% of children during asthma exacerbations. It is possible that viral infection, and in particular human rhino virus infection, is the final trigger which starts an exacerbation. 12
Asthma is commoner in the first born and it is possible that the children of larger families are exposed to more infection (brought into the house by older siblings) and that such infection may in some way prime the immune system in a manner that protects against asthma. However, no studies have so far demonstrated the importance of viral infection in the induction of asthma.
Indoor environment and housing Individuals in industrialized countries spend the majority of their time indoors. The indoor environment, therefore, is likely to be important as a potential place of exposure to allergens and irritants. There has been interest in the hypothesis that the rise in asthma cases is related to improved thermal insulation of homes; the consequent reduced air movement leading to increased concentrations of house-dust mite, animal hair and other indoor allergens, tobacco smoke, nitrogen oxides from gas cookers 13 and other pollutants. In addition, warmer, moister homes with increasing use of fitted furnishings increases the reservoir of potential allergens and encourages the reproduction of house dust mites. A study in Arrhus, Denmark showed that by designing housing with low humidity, controlled temperature, and improved ventilation, by installing removable furnishings, and by frequently washing and airing bedding, the levels of house-dust mite were significantly reduced. This was associated with significantly reduced bronchial hyper-reactivity and reduced medication requirements among those with asthma living in such homes. There are no long term studies in this area, but it has been claimed that reducing exposure to these allergens could have a large public health benefit in terms of asthma prevention. 14
Occupation Occupational exposure to certain chemicals is a well established cause of asthma. In the UK up to 1500 new cases of asthma each year are attributed to this cause (Table 1). Whilst the individual agents are not likely to be important in the pathogenesis of asthma in the general population, they serve as a useful model for investigating potential environmental and genetic influences in a well defined population (Table 1). The challenge for the next 20 years, therefore, is Table 1--Industrial causes of asthma
Occupation
Agent
Plastics industry Bakers Carpenters, saw mill workers Laboratoryanimalworkers and veterinarians Electrical engineers Farmers, dock workers Rubber processing
Isocyanates,anhydrides, tetramines Hour, amylase Wood dust Dander, urine, proteins Solder flux (colophony) Grain dust (moulds,insects, grain) Formaldehyde, anhydrides
262 CURRENTANAESTHESIAAND CRITICALCARE the challenge of primary prevention of asthma. We must not make premature conclusions, and careful study is required to determine which of many environmental factors is activating an inherited tendency to asthma in more people now than a few decades ago. Until such primary prevention is possible, the goal of asthma care depends upon prompt diagnosis, good treatment of acute exacerbations and control of the long term condition. Management
of the acute exacerbation
Most hospital doctors are familiar with the management of acute exacerbation of asthma, for many this may be the only time they encounter the condition. When managing a patient presenting with wheezing and acute shortness of breath the initial aims are: • • • •
relieve hypoxaemia relieve airway obstruction identify high risk individuals confirm the correct diagnosis
Standard therapy for severe exacerbations is the repeated administration of inhaled beta2-agonists and oral or intravenous corticosteroids, the particular regime depending on the clinician's assessment of severity.
aspergillosis, Churg Strauss syndrome and vocal cord dysfunction may be difficult to diagnose and are frequently not detected in the emergency situation. They will not be discussed further here.
Treatment Oxygen. Should be administered to achieve an arterial oxygen saturation in excess of 90%. Beta2-agonists. Usually administered by nebulization with oxygen. It is initially given every 20 minutes, or even continuously for 1 hour or until a satisfactory response is achieved. If there has been no response to this therapy, or the patient is deteriorating clinically, a nebulized anticholinergic agent should be given, or parenteral administration of aminophylline or a betazagonist considered.
Aminophylline. Given parenterally in the management of acute severe asthma, the use of aminophylline is less common than in the past. Whilst giving little additive bronchodilator effect over beta2-agonists, it may increase respiratory drive and respiratory muscle function and sustain the response to beta2-agonists between doses. A bolus dose should be omitted in those on oral theophyllines.
Assessment History. A brief history will identify high risk individuals (previous hospital admission, a history of poor control or poor compliance), and may point to precipitants (exposure to allergen, recent viral infection, pneumonia), or complications (pneumothorax, pneumonia).
Examination. Physical examination will assist assessment of severity (Table 2), identify those at high risk of requiring ventilatory support, and identify complications.
Investigations. Peak flow and oxygen saturation monitoring, arterial blood gases and chest radiograph.
Differential diagnos&. Exclude other conditions which can present with the expiratory wheeze typical of asthma. The history, examination and chest radiograph should identify the two conditions which commonly mimic asthma in adults: chronic obstructive pulmonary disease and left ventricular failure, but foreign body inhalation, particularly in the younger child, should also be considered. Rarer conditions such as allergic bronchopulmonary Table 2~Assessment of severity Features of severe exacerbation
Respiratory arrest imminent
Exhaustion, drowsiness or confusion Paradoxical thoraco-abdominal movements Audible wheeze, quiet breath sounds Silent chest Pulse rate > 120/min Bradycardia PEFR<50% predicted normalor best PEFR < 33% normalor best Hunched forward, talking in single words or phrases Respiratoryrate > 30/min
Other bronchodilators. Nebulized Ipratropium bromide has been shown in some studies to be as or more effective than nebulized beta2-agonist alone when used in the first hours of an acute attack and is recommended when nebulized beta2-agonists fail to control an attack (British Thoracic Society guidelines). High dose systemic steroids. High dose oral prednisolone is as effective as intravenous steroids. The latter should be used where absorption is in doubt or when vomiting is a problem.
Criteria for hospital admission • Inadequate response within 1-2 hours of commencing treatment in casualty, with persistence of presenting symptoms and Peak Expiratory Flow Rate (PEFR) < 70% of predicted or normal value • Presence of factors indicating high risk of sudden death • Prolonged symptoms prior to current presentation • Difficult home conditions, poor access to medical care • Time of day. There should be a lower threshold for admission in late evening and night than in the early day where several more hours are available for home-administered treatments to work, before the high-risk night and early morning period.
Criteria for admission to intensive care unit • Lack of response to initial therapy in the emergency department
ASTHMA 263 • Deteriorating PEFR, worsening or persisting hypoxia (PaO2 < 8.0 kPa) despite 60% inspired O2, or hypercapnia (> 6.0 kPa) • Signs of impending respiratory arrest (Table 2).
Investigating the circumstances of admission Although official management guidelines may change over time and between countries, the management of the acute exacerbation is very standardized. It would be tempting to view the inpatient with asthma in the same light, and not in terms of-an often complex interplay of medical, social and environmental factors resulting finally in failed control. Equally, in a condition that brings individuals into hospital unwell and sends them home well, it would be easy to regard a single asthma attack as a completed episode. Asthma is a not an acute illness with exacerbations occurring upon a background of good health. It is a chronic inflammatory condition. Airways inflammation is continually present even when the individual may otherwise appear to be well.15 A large number of known, and also unknown, environmental stimuli influence the degree of inflammation at any one time, while any number of psychosocial factors at any one time may influence, for instance, whether an individual takes their medication as prescribed or attends their follow up appointment. For these reasons, asthma management over recent years has focused on the long-term control of airways inflammation, principally with inhaled steroids, and on the exploration of social and environmental factors that may explain why an individual suffers from asthma, and why treatment is failing. The importance of communication
It has been observed that only approximately half of those with severe asthma were taking the necessary inhaled steroids as prescribed by their health professional. 16 Seventy five per cent of hospital admissions could probably have been prevented by different prior management. 17 Over 80% of asthma-related deaths are potentially avoidableJ 8 The problems may lie in four different areas: • • • •
what information is given how the information is given how that information is perceived by the patient the consequences of chronic illness for the patient.
What information is given One area of potential difficulty may be a lack of understanding of asthma among health professionals. This relates to the initial diagnosis of the condition and to subsequent management. This problem has been addressed by national guidelines, such as the British Thoracic Society Guidelines 19 and an International Consensus Report 2°, which serve as an excellent basis for health professional education.
How the information is given Explaining the nature of asthma as a disease, its implications as an illness and communicating information about treatment, is of course vitally important, but the available evidence suggests that we do not do this at all well. Despite the fundamental importance of good inhaler technique to the delivery of most asthma drugs, studies have indicated that two-thirds of patients do not use their inhalers properly, and in a poll of 1630 people with asthma, only 63% had received instructions on inhaler use (Table 3). 21 In the same study, it was revealed that only a minority of patients received written specific information about their drug regime, despite clear evidence that such an approach is effective. As a result, patients leave a consultation not understanding their condition, and unsure of what medicines to take, how, or why and with unexpressed fears or concerns which lead to diminished satisfaction and act as a barrier to effective care. Good communication between patient and health professional is an essential prerequisite to good compliance, yet a recent survey suggests that less than a quarter of patients were satisfied with the communication aspects of their care (Table 4). 21 Clearly, as this and other studies of a similar nature show, more time and more efficient methods need to be used to supply our patient's information needs. The type of methods chosen should depend on the individual concerned; videos 22 rather than booklets, for instance, can be helpful in describing asthma to people with poor literacy skills, while group education is effective 23 for certain subgroups of patients. Important too, is the nature of the regime offered. Multiple medications, different doses and variable regimes have all been associated with poor compliance.
Repetition of advice For the majority of patients, a conventional consultation is an intense and stressful experience; they have already had to sit, sometimes for long periods, in a crowded waiting room full of other ill and anxious people. They are ushered into a bare and uncomfortable room to be Table 3--Information awareness among asthma patients Information type
Had a demonstration of their inhaler device Advised what to do in the event of their asthma worsening Received booklets / leaflets about asthma Written information about how / when to take medicines Watched videos about asthma
Total (%)
63 47 39 27 4
Table 4~Patient satisfaction with communicationlevels Feeling at time of diagnosis
Wanted more information Lacked understanding of condition Felt they had had a good discussion with doctor or nurse Felt they had been given plenty of information
Total (%)
55 44 22 9
264 CURRENT ANAESTHESIA AND CRITICAL CARE asked a series of often emotive or personal questions by a person that they may not have met before. They then undress and are examined by the same person before being given instructions on something about which they may not have given a moment's thought before then. It is perhaps not surprising that in studies of both hospital and general practice, 50% of patients have forgotten advice given to them if questioned immediately following a consultation. By repeating the advice during the course of the consultation, and afterwards, the accuracy of recollection improves considerably) 4 Follow-up by nurse specialists, either in outpatients or in the community, may be helpful. Phone-in asthma advice centres may be useful in providing advice between consultations, as are reminder letters sent to patients in between outpatient consultations. 25 Sending a copy of the correspondence with the primary care physician to the patient can also be helpful.
The patient's perception of illness There would be little point in giving optimal treatment, with the most careful advice, if the reason a child wished to get better was so that he could go and play with the new pet that brought on his asthma in the first place. This situation may arise if the patient and the doctor are trying to achieve different goals. Health professionals look at asthma in terms of peak flows and nocturnal wakening, whereas a patient's idea of good control may be completely different. This will depend on the patient's perception of how serious the condition is, how important it is to do something about it, how effective that treatment is, what side effects the treatment has, either experienced or potential, and what are the costs to the patient, both economic and social. In a consultation it may not be immediately apparent how an individual feels about their illness. Understanding common concerns about the long-term risks of inhaled steroids, the risks of asthma drugs during pregnancy or fears about how to react in the face of a severe exacerbation, allows the health professional to explore an individual's perception of their illness. In the same way, explaining common misconceptions, for instance the importance of taking inhaled steroids even when well, enables professional and patient to begin talking on the same wavelength. Each individual has a different experience of their illness and, along with this, their own anxieties and preconceptions. The use of open-ended questions may reveal unspoken concerns. "What do you think makes your asthma worse?" A patient may erroneously date their asthma to a particular event or activity. Whilst this may be relevant to the control of their asthma, avoidance of a presumed may be needlessly be interfering with a person's lifestyle.
Different individuals may have different expectations of asthma control and may be prepared to tolerate more or less interference with their lifestyle to achieve this control. Optimal control is more important to an athlete than to, for instance, an elderly person with arthritis. "How does asthma affect your life?"
The consequences of illness Despite the best efforts of both the health professional and the patient, in a proportion of cases there will still be misunderstandings, the control of symptoms may still not reach patient expectations, or the sacrifices made to achieve adequate control may be unacceptable. This sense of loss of control in an individual's life leads to feelings of helplessness, feelings of poor self esteem and depression. This is compounded by the fact that 'control' is perceived as being in the hands of others, the health professionals. The denial or anger that patients often feel is their way of dealing with this situation, and as a result there may be a sense of conflict with, or animosity towards, providers of care. Poor compliance is one understandable consequence. One way of breaking this cycle is to allow the patient to control the management of their own condition. This involves the patient themselves changing their medication according to written advice, depending on how well-controlled their asthma is at a particular time. The individual assesses their control using a combination of symptoms and peak flow rate. They are taught what symptoms indicate worsening asthma, what peak flow rates indicate that treatment changes are needed, and what to do in the event of a severe exacerbation. Evaluation of this approach has shown a significant reduction in morbidity in several studies. 26'27 Every patient who has been hospitalized with acute asthma should be regarded as at risk of further severe attacks and offered a written self-management plan.
Key points The prevalence of asthma is increasing. Genetic factors may determine an individual's relative risk of developing asthma but the major determinants and the reasons for the recent increases are likely to be environmental. The environmental influence on asthma is multi-factorial. House-dust mite and animal hair are probably important factors, possibly because of changes in housing, but dietary changes may enhance the effects of these other environmental influences.
"What do you expect from your treatment?"
Pollution and smoking are less important than previously assumed, although maternal smoking may have particular importance in childhood asthma.
"If we could improve one aspect of your condition what would that be?"
For the time being, advances in the understanding of asthma have had little impact on asthma management.
ASTHMA
For the foreseeable future, improvements in asthma control are only likely through more effective communication between the health professional and the patient, and through more control of the condition being given to the people who suffer from it.
References 1. Central Health Monitoring Unit, Department of Health. Asthma an epidemiological overview. HMSO, 1995. 2. Ninan T K, Russell G. Respiratory symptoms and atopy in Aberdeen schoolchildren: evidence from two surveys 25 year apart. BMJ 1992; 04: 875-875. 3. Waite D A, Eyles E F, Tonkin S L, O'Donnell T V. Asthma prevalence in Tokelauan children in two environments. Clin Allergy 1980; 10: 71-75. 4. Van Niererk C H, Weinberg E G, Shore S C, Heese H DeV, Schalioyk D J. Prevalence of asthma: a community study of urban and rural Xhosa. Clin Allergy 1979; 9: 319-324. 5. Bjorksten F, Suoiemi I, Koski V. Neonatal birch pollen contact and subsequent allergy to birch pollen. Clin Allergy 1980; 10: 585-591. 6. Sporick R, Holgate S T, Platts-Mills T A E, Cogswell J J. Exposure to house dust mite allergy (Der p 1) and the development of asthma in childhood. N Engl J Med 1990; 323: 502-507. 7. Austin J B, Russell G, Adam M G, et al. Arch Dis childhood 1994; 71: 211-216. 8. Schachter E N, Witek T J, Berk G J, Hosein H R, Colic G, Caen W. Airway effects of low concentration of sulphur dioxide: dose response characteristics. Arch Environ Health 1984; 39: 34-42. 9. Biagini R E, Moorman W J, Louis T R, Bemstein I L. Ozone enhancement of platinum asthma in a primate model. A m Rev Respir Dis 1986; 134: 719-725. 10. Celenza A, et al. Thunderstorm associated asthma: a detailed analysis of environmental factors. BMJ 1996; 312: 604-607. 11. Britton J R, Pavord D, Richards K A, et al. Dietary antioxidant vitamin intake and lung function in the general population. A m J Respir Crit Care Med 1995; 151: 1383-1387. 12. Johnston S L, Paitermore S K, et al. A community study of the role of viral infection in exacerbation of asthma in 9-11-year-old
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children. BMJ 1995; 310: 1225-1229. 13. Jarvis D, Chinn S, Luczynska C, Burney E Association of respiratory symptoms and lung function in young adults with use of domestic appliances. Lancet 1996; 347:426-431. 14. Peat J K, Tovey E, Toelle B G, et al. House dust mite allergens; a major risk factor for childhood asthma in Australia. A m J Respir Crit Care Med 1996; 153: 141-146. 15. NHBLI/WHO Workshop report. Global Strategy for Asthma Management and Prevention. Betheseda: National Heart, Lung and Blood Institute, January 1995: Publication no. 95-3659. 16. Partridge M R. Delivering optimal care to the person with asthma: what are the key components and what do we mean by patient education. Eur Respi Med 1995; 8: 298-305. 17. Blainey A D, Beale A, Lomas D, Partridge M R. The cost of acute asthma. How much is preventable? Health Trends 1991; 22: 151-153. 18. British Thoracic Association. Deaths from asthma in two regions of England. BMJ 1981; 285: 1251-1255. 19. British Thoracic Society, Paediatric Association, Royal College of Physicians of London, National Asthma Campaign, et al. Guidefines on the management of asthma. Thorax 48 S1-24 (and summary charts). BMJ 1993; 306: 776-782. 20. National Heart Blood and Lung Institute, National Institutes of Health. International concensus report on diagnosis and management of asthma. Eur Resp J 1992; 5: 601-641. 21. Partridge M R. Asthma: lessons from patient education. Patient Education and Counseling 1995; 26: 81-85. 22. Partridge M R. Asthma education: more reading or more viewing? J R Soc Med 1986; 79: 326-328. 23. Wilson S R, Scamagas P, German D F, et al. A controlled trial of two forms of self management education for adults with asthma. A m J Med 1993; 94: 564-576. 24. Evans D. To help patients control asthma the clinician must be a good listener and teacher. Thorax 1993; 48: 685-687. 25. Osman I, Abdalla M I, Beattie J A G, et al. Reducing hospital admissions through computer supported education for asthma patients. BMJ 1994: 308: 568-571. 26. Leadensuo A, Haahtela T, Heerala J, et al. Randomised comparision of graded self-management and traditional treatment of asthma over one year. BMJ 1996; 312: 48-52. 27. Ignacio G. Asthma self management programme by home monitoring of peak expiratory monitoring. A m J Resp Crit Care Med 1995; 151: 353-359.
© 1996 PearsonProfessionalLtd
Medicine
Asthma: a changing perspective on management
R T. F l o o d - p a g e and M. R. Partridge
In understanding the role of environmental factors in the pathogenesis of asthma, it is important to make the distinction between causes of asthma and exacerbants (which worsen existing asthma). Agents causing asthma are thought to sensitize the bronchial mucosa so that subsequent exposure to agents which exacerbate asthma may result in the mucosal inflammation and bronchial wall constriction characteristic of the disease.
Asthma is a common condition. It is estimated to affect around 5% of adults in the UK and between 10% and 15% of children. In addition, 4% of adults and 6% of children are estimated to have asthma of severity sufficient to require regular medical supervision.1 It has significant socio-economic importance; 11 million working days each year are lost because of asthma, costing an estimated £550 million in lost productivity. Its cost to the health services is estimated at £450 million. In the UK the estimated number of hospital deaths and discharges due to asthma doubled between 1979 and 1985. The number of prescriptions for asthma has doubled over the same period. ~ The reasons for the increasing burden from this disease are not clear.
Timing of exposure Sensitization in utero and in infancy
There has been a lot of recent interest concerning when in an individual's life sensitization occurs. One Scandinavian study showed that birch pollen allergy in children occurs more frequently in those born just before the pollen season. 5 Another study compared the development of skin prick allergy to dog hair in households with a dog throughout pregnancy, with those introducing a dog later, or with no dog at all. The likelihood of developing allergy appeared to be greatest from the second trimester of pregnancy until the end of the first year. Similarly, increased house-dust mite exposure during the first two years of life appears to be associated with an increased skin prick response and increase in asthma prevalence in adolescence. 6
T h e i m p o r t a n c e o f the e n v i r o n m e n t
Even allowing for differences in diagnostic fashion and in methods of detection, asthma prevalence has doubled over the last 2-3 decades. 2 Our genetic make-up could not have changed over this time and for this reason there is general agreement that while genetics plays a significant role in determining who is at risk of developing allergic disease, changes in our environment are more likely to explain the increase in prevalence. This seems to be borne out by a series of studies demonstrating a markedly higher prevalence of asthma in the offspring of migrants to urban areas when compared to the offspring of those who remained in their rural community of origin. 3'4
Possible initiating agents Atmospheric pollution
One area which attracts debate is the importance of air pollution in urban areas, principally oxides of nitrogen, ozone, sulphur dioxide and particulate matter. The migration studies previously discussed would suggest that pollution might be important but urbanization is also
Dr Patrick T. Flood-page MB MRCP madDr Martyn R. Partridge MD FRCP, Chest Clinic,Whipps Cross Hospital,LondonE11 1NR, UK. Correspondenceto Dr M. R. Partridge.
260
ASTHMA 261 associated with changes in diet, changes in housing and smoking habits. A study of the prevalence of asthma in rural and urban areas of Scotland, where confounding factors such as housing and diet are more likely to be constant, showed no differences] Whilst studies have clearly shown that air pollutants can both provoke acute airways narrowing and can enhance the sensitivity of airways to other allergens, 8"9no study has convincingly demonstrated an association between the severity of pollution and the causation of asthma. Moreover, as asthma has been increasing in the past 30 years, pollution levels have not significantly increased.
Plant aeroallergens Pollen and other plant-derived airborne particles have long been recognized as triggers of asthma. Birch pollen has been implicated in neonatal sensitization and raised pollen counts have been connected with seasonal peaks in asthma exacerbations and most recently with thunderstorm-related asthma epidemics. ~° Although important as a cause of asthma exacerbations in susceptible individuals, pollen is unlikely to explain the recent increase in prevalence of asthma.
Tobacco smoking Smoking significantly increases the risk of asthma in the offspring of women who smoke during pregnancy and in children exposed to cigarette smoke in the home. This effect is lost as the child gets older and by the age of fifteen there is no significant association. Smoking in adulthood may exacerbate pre-existing asthma, and for certain agents the incidence of occupational asthma is higher amongst smokers, but in other situations smoking has not been shown to predispose to the development of asthma.
Diet Over the last 40 years diet in the western world has changed considerably. In the UK, the population now consumes 50% less fresh vegetables, 30% less fruit and proportionally more processed food. The first change that accompanies urbanization in developing countries is this change in diet towards processed food. It is conceivable that this is connected to the increase in asthma and may reflect an increased susceptibility to develop asthma consequent upon altered dietary antioxidant levels, u
Respiratory virus infections Recent research using PCR (polymerase chain reaction) techniques detected evidence of viral infection in 73% of children during asthma exacerbations. It is possible that viral infection, and in particular human rhino virus infection, is the final trigger which starts an exacerbation. 12
Asthma is commoner in the first born and it is possible that the children of larger families are exposed to more infection (brought into the house by older siblings) and that such infection may in some way prime the immune system in a manner that protects against asthma. However, no studies have so far demonstrated the importance of viral infection in the induction of asthma.
Indoor environment and housing Individuals in industrialized countries spend the majority of their time indoors. The indoor environment, therefore, is likely to be important as a potential place of exposure to allergens and irritants. There has been interest in the hypothesis that the rise in asthma cases is related to improved thermal insulation of homes; the consequent reduced air movement leading to increased concentrations of house-dust mite, animal hair and other indoor allergens, tobacco smoke, nitrogen oxides from gas cookers 13 and other pollutants. In addition, warmer, moister homes with increasing use of fitted furnishings increases the reservoir of potential allergens and encourages the reproduction of house dust mites. A study in Arrhus, Denmark showed that by designing housing with low humidity, controlled temperature, and improved ventilation, by installing removable furnishings, and by frequently washing and airing bedding, the levels of house-dust mite were significantly reduced. This was associated with significantly reduced bronchial hyper-reactivity and reduced medication requirements among those with asthma living in such homes. There are no long term studies in this area, but it has been claimed that reducing exposure to these allergens could have a large public health benefit in terms of asthma prevention. 14
Occupation Occupational exposure to certain chemicals is a well established cause of asthma. In the UK up to 1500 new cases of asthma each year are attributed to this cause (Table 1). Whilst the individual agents are not likely to be important in the pathogenesis of asthma in the general population, they serve as a useful model for investigating potential environmental and genetic influences in a well defined population (Table 1). The challenge for the next 20 years, therefore, is Table 1--Industrial causes of asthma
Occupation
Agent
Plastics industry Bakers Carpenters, saw mill workers Laboratoryanimalworkers and veterinarians Electrical engineers Farmers, dock workers Rubber processing
Isocyanates,anhydrides, tetramines Hour, amylase Wood dust Dander, urine, proteins Solder flux (colophony) Grain dust (moulds,insects, grain) Formaldehyde, anhydrides
262 CURRENTANAESTHESIAAND CRITICALCARE the challenge of primary prevention of asthma. We must not make premature conclusions, and careful study is required to determine which of many environmental factors is activating an inherited tendency to asthma in more people now than a few decades ago. Until such primary prevention is possible, the goal of asthma care depends upon prompt diagnosis, good treatment of acute exacerbations and control of the long term condition. Management
of the acute exacerbation
Most hospital doctors are familiar with the management of acute exacerbation of asthma, for many this may be the only time they encounter the condition. When managing a patient presenting with wheezing and acute shortness of breath the initial aims are: • • • •
relieve hypoxaemia relieve airway obstruction identify high risk individuals confirm the correct diagnosis
Standard therapy for severe exacerbations is the repeated administration of inhaled beta2-agonists and oral or intravenous corticosteroids, the particular regime depending on the clinician's assessment of severity.
aspergillosis, Churg Strauss syndrome and vocal cord dysfunction may be difficult to diagnose and are frequently not detected in the emergency situation. They will not be discussed further here.
Treatment Oxygen. Should be administered to achieve an arterial oxygen saturation in excess of 90%. Beta2-agonists. Usually administered by nebulization with oxygen. It is initially given every 20 minutes, or even continuously for 1 hour or until a satisfactory response is achieved. If there has been no response to this therapy, or the patient is deteriorating clinically, a nebulized anticholinergic agent should be given, or parenteral administration of aminophylline or a betazagonist considered.
Aminophylline. Given parenterally in the management of acute severe asthma, the use of aminophylline is less common than in the past. Whilst giving little additive bronchodilator effect over beta2-agonists, it may increase respiratory drive and respiratory muscle function and sustain the response to beta2-agonists between doses. A bolus dose should be omitted in those on oral theophyllines.
Assessment History. A brief history will identify high risk individuals (previous hospital admission, a history of poor control or poor compliance), and may point to precipitants (exposure to allergen, recent viral infection, pneumonia), or complications (pneumothorax, pneumonia).
Examination. Physical examination will assist assessment of severity (Table 2), identify those at high risk of requiring ventilatory support, and identify complications.
Investigations. Peak flow and oxygen saturation monitoring, arterial blood gases and chest radiograph.
Differential diagnos&. Exclude other conditions which can present with the expiratory wheeze typical of asthma. The history, examination and chest radiograph should identify the two conditions which commonly mimic asthma in adults: chronic obstructive pulmonary disease and left ventricular failure, but foreign body inhalation, particularly in the younger child, should also be considered. Rarer conditions such as allergic bronchopulmonary Table 2~Assessment of severity Features of severe exacerbation
Respiratory arrest imminent
Exhaustion, drowsiness or confusion Paradoxical thoraco-abdominal movements Audible wheeze, quiet breath sounds Silent chest Pulse rate > 120/min Bradycardia PEFR<50% predicted normalor best PEFR < 33% normalor best Hunched forward, talking in single words or phrases Respiratoryrate > 30/min
Other bronchodilators. Nebulized Ipratropium bromide has been shown in some studies to be as or more effective than nebulized beta2-agonist alone when used in the first hours of an acute attack and is recommended when nebulized beta2-agonists fail to control an attack (British Thoracic Society guidelines). High dose systemic steroids. High dose oral prednisolone is as effective as intravenous steroids. The latter should be used where absorption is in doubt or when vomiting is a problem.
Criteria for hospital admission • Inadequate response within 1-2 hours of commencing treatment in casualty, with persistence of presenting symptoms and Peak Expiratory Flow Rate (PEFR) < 70% of predicted or normal value • Presence of factors indicating high risk of sudden death • Prolonged symptoms prior to current presentation • Difficult home conditions, poor access to medical care • Time of day. There should be a lower threshold for admission in late evening and night than in the early day where several more hours are available for home-administered treatments to work, before the high-risk night and early morning period.
Criteria for admission to intensive care unit • Lack of response to initial therapy in the emergency department
ASTHMA 263 • Deteriorating PEFR, worsening or persisting hypoxia (PaO2 < 8.0 kPa) despite 60% inspired O2, or hypercapnia (> 6.0 kPa) • Signs of impending respiratory arrest (Table 2).
Investigating the circumstances of admission Although official management guidelines may change over time and between countries, the management of the acute exacerbation is very standardized. It would be tempting to view the inpatient with asthma in the same light, and not in terms of-an often complex interplay of medical, social and environmental factors resulting finally in failed control. Equally, in a condition that brings individuals into hospital unwell and sends them home well, it would be easy to regard a single asthma attack as a completed episode. Asthma is a not an acute illness with exacerbations occurring upon a background of good health. It is a chronic inflammatory condition. Airways inflammation is continually present even when the individual may otherwise appear to be well.15 A large number of known, and also unknown, environmental stimuli influence the degree of inflammation at any one time, while any number of psychosocial factors at any one time may influence, for instance, whether an individual takes their medication as prescribed or attends their follow up appointment. For these reasons, asthma management over recent years has focused on the long-term control of airways inflammation, principally with inhaled steroids, and on the exploration of social and environmental factors that may explain why an individual suffers from asthma, and why treatment is failing. The importance of communication
It has been observed that only approximately half of those with severe asthma were taking the necessary inhaled steroids as prescribed by their health professional. 16 Seventy five per cent of hospital admissions could probably have been prevented by different prior management. 17 Over 80% of asthma-related deaths are potentially avoidableJ 8 The problems may lie in four different areas: • • • •
what information is given how the information is given how that information is perceived by the patient the consequences of chronic illness for the patient.
What information is given One area of potential difficulty may be a lack of understanding of asthma among health professionals. This relates to the initial diagnosis of the condition and to subsequent management. This problem has been addressed by national guidelines, such as the British Thoracic Society Guidelines 19 and an International Consensus Report 2°, which serve as an excellent basis for health professional education.
How the information is given Explaining the nature of asthma as a disease, its implications as an illness and communicating information about treatment, is of course vitally important, but the available evidence suggests that we do not do this at all well. Despite the fundamental importance of good inhaler technique to the delivery of most asthma drugs, studies have indicated that two-thirds of patients do not use their inhalers properly, and in a poll of 1630 people with asthma, only 63% had received instructions on inhaler use (Table 3). 21 In the same study, it was revealed that only a minority of patients received written specific information about their drug regime, despite clear evidence that such an approach is effective. As a result, patients leave a consultation not understanding their condition, and unsure of what medicines to take, how, or why and with unexpressed fears or concerns which lead to diminished satisfaction and act as a barrier to effective care. Good communication between patient and health professional is an essential prerequisite to good compliance, yet a recent survey suggests that less than a quarter of patients were satisfied with the communication aspects of their care (Table 4). 21 Clearly, as this and other studies of a similar nature show, more time and more efficient methods need to be used to supply our patient's information needs. The type of methods chosen should depend on the individual concerned; videos 22 rather than booklets, for instance, can be helpful in describing asthma to people with poor literacy skills, while group education is effective 23 for certain subgroups of patients. Important too, is the nature of the regime offered. Multiple medications, different doses and variable regimes have all been associated with poor compliance.
Repetition of advice For the majority of patients, a conventional consultation is an intense and stressful experience; they have already had to sit, sometimes for long periods, in a crowded waiting room full of other ill and anxious people. They are ushered into a bare and uncomfortable room to be Table 3--Information awareness among asthma patients Information type
Had a demonstration of their inhaler device Advised what to do in the event of their asthma worsening Received booklets / leaflets about asthma Written information about how / when to take medicines Watched videos about asthma
Total (%)
63 47 39 27 4
Table 4~Patient satisfaction with communicationlevels Feeling at time of diagnosis
Wanted more information Lacked understanding of condition Felt they had had a good discussion with doctor or nurse Felt they had been given plenty of information
Total (%)
55 44 22 9
264 CURRENT ANAESTHESIA AND CRITICAL CARE asked a series of often emotive or personal questions by a person that they may not have met before. They then undress and are examined by the same person before being given instructions on something about which they may not have given a moment's thought before then. It is perhaps not surprising that in studies of both hospital and general practice, 50% of patients have forgotten advice given to them if questioned immediately following a consultation. By repeating the advice during the course of the consultation, and afterwards, the accuracy of recollection improves considerably) 4 Follow-up by nurse specialists, either in outpatients or in the community, may be helpful. Phone-in asthma advice centres may be useful in providing advice between consultations, as are reminder letters sent to patients in between outpatient consultations. 25 Sending a copy of the correspondence with the primary care physician to the patient can also be helpful.
The patient's perception of illness There would be little point in giving optimal treatment, with the most careful advice, if the reason a child wished to get better was so that he could go and play with the new pet that brought on his asthma in the first place. This situation may arise if the patient and the doctor are trying to achieve different goals. Health professionals look at asthma in terms of peak flows and nocturnal wakening, whereas a patient's idea of good control may be completely different. This will depend on the patient's perception of how serious the condition is, how important it is to do something about it, how effective that treatment is, what side effects the treatment has, either experienced or potential, and what are the costs to the patient, both economic and social. In a consultation it may not be immediately apparent how an individual feels about their illness. Understanding common concerns about the long-term risks of inhaled steroids, the risks of asthma drugs during pregnancy or fears about how to react in the face of a severe exacerbation, allows the health professional to explore an individual's perception of their illness. In the same way, explaining common misconceptions, for instance the importance of taking inhaled steroids even when well, enables professional and patient to begin talking on the same wavelength. Each individual has a different experience of their illness and, along with this, their own anxieties and preconceptions. The use of open-ended questions may reveal unspoken concerns. "What do you think makes your asthma worse?" A patient may erroneously date their asthma to a particular event or activity. Whilst this may be relevant to the control of their asthma, avoidance of a presumed may be needlessly be interfering with a person's lifestyle.
Different individuals may have different expectations of asthma control and may be prepared to tolerate more or less interference with their lifestyle to achieve this control. Optimal control is more important to an athlete than to, for instance, an elderly person with arthritis. "How does asthma affect your life?"
The consequences of illness Despite the best efforts of both the health professional and the patient, in a proportion of cases there will still be misunderstandings, the control of symptoms may still not reach patient expectations, or the sacrifices made to achieve adequate control may be unacceptable. This sense of loss of control in an individual's life leads to feelings of helplessness, feelings of poor self esteem and depression. This is compounded by the fact that 'control' is perceived as being in the hands of others, the health professionals. The denial or anger that patients often feel is their way of dealing with this situation, and as a result there may be a sense of conflict with, or animosity towards, providers of care. Poor compliance is one understandable consequence. One way of breaking this cycle is to allow the patient to control the management of their own condition. This involves the patient themselves changing their medication according to written advice, depending on how well-controlled their asthma is at a particular time. The individual assesses their control using a combination of symptoms and peak flow rate. They are taught what symptoms indicate worsening asthma, what peak flow rates indicate that treatment changes are needed, and what to do in the event of a severe exacerbation. Evaluation of this approach has shown a significant reduction in morbidity in several studies. 26'27 Every patient who has been hospitalized with acute asthma should be regarded as at risk of further severe attacks and offered a written self-management plan.
Key points The prevalence of asthma is increasing. Genetic factors may determine an individual's relative risk of developing asthma but the major determinants and the reasons for the recent increases are likely to be environmental. The environmental influence on asthma is multi-factorial. House-dust mite and animal hair are probably important factors, possibly because of changes in housing, but dietary changes may enhance the effects of these other environmental influences.
"What do you expect from your treatment?"
Pollution and smoking are less important than previously assumed, although maternal smoking may have particular importance in childhood asthma.
"If we could improve one aspect of your condition what would that be?"
For the time being, advances in the understanding of asthma have had little impact on asthma management.
ASTHMA
For the foreseeable future, improvements in asthma control are only likely through more effective communication between the health professional and the patient, and through more control of the condition being given to the people who suffer from it.
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