Bronchial Asthma

Asthma is characterized by paroxysmal and reversible obstruction of the airways. It is this reversibility that distinguishes asthma from COPD although the reversibility is relative rather than absolute. People with severe asthma may never achieve completely normal parameters for lung function and COPD is rarely totally refractory to medication. Asthma may progress to COPD, especially in those who smoke. Diagnosing COPD is discussed elsewhere.

There are two components to asthma. One is spasm of the smooth muscle that pulls on the cartilaginous support of the airways and in doing so narrows them. The other is an excessive production of secretions. Asthma is an inflammatory disease. When people have died of acute asthma, postmortem examination shows that the airways are blocked by secretions. It is imperative to treat this inflammatory reaction energetically.

In 1990 asthma was considered a suitable topic for the encouragement of clinics in General Practice and in 2004 it became an important component of the Qualities and Outcomes Framework.¹

A problem with quoting figures for the prevalence of asthma is the variability of criteria for diagnosis.²This is a very common condition and it has become more common in recent years. Some of this may be due to greater interest in the condition and so more frequent diagnosis but this will not account for all of the rise in prevalence. The numbers in a practice, based on an age/sex/disease register are probably a significant overestimate as a great many children and young people outgrow asthma but the diagnosis is not removed. It should be changed to past history of asthma as such people may still wheeze with a URTI and it is unwise to use beta blockers if there is an alternative.

Government statistics show a peak prevalence between 5 and 15, falling thereafter until 55 to 64 years old when it starts to rise again.³ Between 1994 and 1998, the total number of cases rose from 33,017 males and 33,464 females to 43,035 males and 46,348 females. There is a slight male preponderance in childhood with a reversal in early adulthood.

The history is extremely important as patients may present between acute attacks and so examination and investigation may be completely normal. The paroxysmal nature of the condition is important. Wheezing or ronchi is seen as the cardinal feature but this can be misleading. Breath sounds, heart sounds and heart murmurs are all caused by turbulence in a fluid (liquid or gas) medium. If there is no turbulence there is no sound. Laminar flow is silent. Hence mild asthma may be just a cough and severe asthma can be life-threatening and too tight to wheeze.

Ask what happens in an attack. There are a number of possibilities:

• Wheezing is common but not invariable
• Coughing is common
• Shortness of breath
• Tightness and perhaps pain in the chest

Ask if there is an obvious precipitating or aggravating factor for attacks. There may be none:

• URTIs.
• Cold air. Ask about going out on a cold morning. If this causes pain in the chest in an adult, it may be angina.
• It may occur during exercise but more classically it is after exercise. Running is worse than cycling and it is uncommon on swimming.
• Pollution, especially cigarette smoke. Pollens and chemicals may also be implicated.
• It may follow exposure to animals such as cats, dogs or horses.
• Note the time of day when it happens. There is a natural dip in peak flow overnight and in a vulnerable person this may precipitate or aggravate symptoms. It may cause nocturnal waking or simply being rather short of breath or wheezy in the morning.

If asthma appears to be related to occupation, this has significant implications and it may be wise to refer the person to a chest physician or an occupational physician. Occupational asthma is discussed elsewhere.

Past, Present and Family History

• Atopic eczema, asthma and hayfever tend to run together in individuals and in families.
• Ask about drugs. The patient may have been started on a beta blocker recently. This includes drops for glaucoma. Sometimes medications to dry secretions can aggravate symptoms and they may be OTC. They make the secretions in the chest too dry and viscous to move. The association between NSAIDs, including aspirin, and the precipitation of asthma is well documented but in reality it is not very often seen.
• Ask about smoking. This includes passive smoking. Children are not the only ones who suffer. A member of the household may smoke indoors.

Diagnosis in Children

Diagnosis in children can pose difficulties. Asthma should be suspected in any child with wheezing, ideally heard by a health professional on auscultation and distinguished from other upper airway noises.⁴ If asthma occurs in young babies, there is usually a strong family history and it has not been present from birth. If there is doubt, seek an expert opinion.

Confirm aggravating factors. These may include colds, running around (perhaps the child is less energetic than his peers), and cold air. Ask about night time cough. Ask about smoke in the household.

Respiratory system, history and examination, has been covered elsewhere. The chest should be examined although if the patient is between attacks it may be normal. However, he may present in moderate or severe distress and there are several matters to note.

• Before examining the chest, check the pulse rate. This may be artificially elevated by excessive use of beta agonists but nevertheless, tachycardia is a significant feature. Respiratory rate above 25 a minute and heart rate above 110 per minute are regarded a significant signs in adults.
• Look at the patient breathing.
  • Is it fast?
  • Is it laboured?
  • Does he look anxious?
  • Can he speak in full sentences?
  • Is he using accessory muscles of respiration?
  • Does he breathe out through pursed lips?
• Note the ratio between the inspiratory and expiratory phase. Usually this can be assessed by counting one on the way in and one, two on the way out. This 2:1 ratio of expiratory to inspiratory pase is normal. The longer the expiratory phase compared with the inspiratory phase, the more severe the obstruction.
• The chest may appear hyperinflated
• In a small child there may be intercostal recession
• Check that there is no deviation of the trachea or abnormalities on percussion to suggest pneumonia, pulmonary collapse or pneumothorax
• There may be diffuse expiratory ronchi. If they are not diffuse, especially in a child, there may have been inhalation of a foreign body. There may be inspiratory ronchi too. If ronchi are predominantly inspiratory and the inspiratory phase is prolonged, this suggests that airways obstruction is outside the chest.

Asthma is a very common condition but there are many other diagnoses that must be considered. Not all asthma wheezes and all that wheezes is not asthma. The problem of wheezing in children is discussed elsewhere. The main differential diagnoses vary according to whether the patient is an adult of a child.

Children

• Especially if the problem appears to have been present since birth, consider cystic fibrosis. It may also cause severe infections and a persistent cough.
• Babies may have aspiration. Gastro-oesophageal reflux can cause a cough when lying down.
• Inhalation of a foreign body can occur at all ages. The infant may be at the stage of putting things in the mouth or an older child may have thrown up a peanut to catch in the mouth and be reluctant to admit it. Peanuts tend to go straight down to the right main bronchus and cause considerable inflammation and obstruct the right lower lobe.
• Postnasal drip causes a cough, worse at night
• Inspiratory stridor and wheeze suggest a laryngeal disorder including croup
• Focal signs may suggest bronchiectasis or tuberculosis. The latter is very important if the child is from a high risk family.

Adults

• Asthma can progress to COPD, especially in smokers. The vast majority of patients with COPD do or have smoked. The essential difference between this and asthma is reversibility.
• Heart failure can cause nocturnal cough and cardiac asthma
• A tightness or pain in the chest, especially on meeting a stiff wind on a cold morning, may be asthma or angina
• Remember malignancy, especially in smokers. Look for clubbing that also occurs in bronchiectasis. Malignancy is not just lung cancer but may be in the upper airways.
• Gastro-oesophageal reflux can cause nocturnal cough and a postnasal drip may cause more coughing when lying down
• Pulmonary fibrosis or interstitial lung disease
• Recurrent pulmonary embolism
• Tuberculosis
• Is there really wheezing or just shortness of breath on exertion? Causes of the latter include heart failure, severe anaemia and obesity, often aggravated by lack of physical fitness.

Peak Flow

Measurement of peak flow is the simplest and most basic test. Every GP should have a mini Wright's peak flow meter with disposable mouth pieces and a smaller, low reading one is often useful for children and for more severe obstruction. Lung function tests, whether peak flow of spirometry, are unreliable below the age of 5 but for older children and adults it is often helpful to prescribe a Wright's mini peak flow meter for them so that they may monitor their own disease and have objective measurements.

Peak flow is usually estimated with the patient standing, although results are not significantly different if the patient is seated.⁵ He should take in a deep breath and expel it as rapidly as possible into the meter with as much force as he can muster. The very first part is all that matters for this test and it is not necessary to empty the lungs. It is usual to record the best of 3. If the tests show significant improvement from the 1st to the 3rd, it is worth trying a 4th and even 5th attempt as the patient is acquiring the technique.

Charts are available of "normal values". There are different charts for males and females as males tend to have higher peak flows than females, all other parameters being equal. Expected PF increases with increasing height and it varies with age, reaching a peak in the early 20s and then gradually declining. As well as airways obstruction, poor effort or neuromuscular disease will limit performance.

"Normality" may be seen in two ways. One is the listed normal for age, sex and height. The other is normal, or what is good for that individual. Thus a patient with asthma may have a "predicted" PF of 500 l/min but he knows that if he can achieve 400 l/min he is well but if it falls to 300 l/min he has problems and needs to take appropriate action. Thus the PF meter can let the patient manage his own disease with an objective measurement.

Quite often, the single measurement of PF in the surgery is insufficient to confirm or refute a diagnosis of asthma and the patient should be asked to record PF several times a day over a number of days. It is normal for peak flow to fall slightly overnight and these nocturnal dips may be accentuated in asthma. Thus, a marked diurnal variation in peak flow is significant. There may be significant day to day variation and the patient may be able to demonstrate that testing PF after certain aggravating activities causes measurable dips.

Patients with moderate or severe asthma should be encouraged to record their PF twice daily long term. It provides an objective warning of when there is clinical deterioration. It is best recorded on a chart, often in a book, and this graphical representation gives an impressive illustration of variation in performance. The book may be presented for regular review at the asthma clinic or when the patient consults to complain of deterioration in his condition.

Spirometry

Spirometry provides rather more information than peak flow. The machine is much more large and expensive than a peak flow meter and it needs to be calibrated but every practice should have one or have access to one. Spirometry measures the whole volume that may be expelled in one breath. This is vital capacity, not total lung volume as there is a residual capacity. It also permits calculation of the percentage exhaled in the first second, called the FEV₁. It is of more value in COPD than asthma but it can be used to demonstrate reversibility of airways obstruction and may be valuable where the diagnosis is uncertain.

Chest X-ray

Chest x-ray is remarkably normal in even very severe asthma. The value of CXR lies not in evaluating asthma but in excluding other pathology. It should not be used routinely in the assessment of asthma but consider CXR in any patient presenting atypically or with atypical findings.⁴

In most cases it is possible to make a diagnosis based purely on the clinical features but there are times when it is less clear and objective criteria are required. BTS/SIGN guidelines⁴ make the following suggestions:

• Diurnal variation of peak flow in excess of 20% for at least 3 days in a week, based on a peak flow diary over 2 weeks.
• Spirometry shows an increase in FEV₁ of at least 15% and in excess of 200ml/min after use of a beta agonist. This would normally be salbutamol 400μg (4 puffs) by MDI or 2.5mg by nebuliser.
• The same improvement in spirometry after a course of steroids. They recommend oral prednisolone at 30mg daily for 14 days. Many people would be happy with a shorter or less intensive course.
• FEV₁ decreases by at least 15% after running for 6 minutes.
• In difficult cases a histamine or metacholine challenge may be used but these tend to be the province of specialists or GPs with special interests.

Such criteria are not appropriate for young children and they suggest that there should be careful consideration of the key features and an open mind to alternative diagnoses. Assess the response to treatment and if it is ineffective, reconsider the diagnosis. The BTS states that asthma may be confirmed if all three of the following apply:

• Variable symptoms of wheeze, cough, shortness of breath, chest tightness and family or personal history of atopy
• The 20% variability in lung function as described above
• Symptomatic response to inhaled beta agonist, oral or inhaled steroids

See Acute severe asthma and status asthmaticus.

When reviewing patients there are 3 basic questions suggested by the Royal College of Physicians to cover the ground efficiently.

• Have you had any difficulty sleeping because of your asthma symptoms, including cough?
• Have you had your usual asthma symptoms during the day (cough, wheeze, chest tightness of breathlessness)?
• Has your asthma interfered with you usual activities (housework, work, school, etc)?

The revised Jones morbidity Index⁶ asks 3 questions:

• Have you been in a wheezy or asthmatic condition at least once a week?
• Have you had time off work or school because of your asthma?
• Have you suffered from attacks of wheezing during the night?
  • NO to all questions = LOW morbidity
  • One YES answer = MEDIUM morbidity
  • Two or three YES answers = HIGH morbidity

Even in practices with good resources, there is a great morbidity from inadequately controlled asthma.⁷

Management of asthma in adults and asthma in children is discussed elsewhere and so this section will be confined to general principles. The management of asthma is based on 4 principles:

• Control symptoms, including nocturnal symptoms and those related to exercise
• Prevent exacerbations
• Achieve best possible lung function
• Minimise side effects

To achieve this:

• Start at the appropriate step according to the severity of the presenting condition
• Achieve early control
• Step up or down the medication to enable optimum control without excessive medication

Delivery of drugs to the lungs is a very efficient method in terms of both swiftness of action and limitation of systemic dose. However, it is essential to ascertain that the patient is competent at using the inhaler. Simply giving a prescription for a MDI is not good enough and steps must be taken to teach the patient to use the device and to check that he is doing it properly. There are many types of inhaler and they can be used by even the very young. The choice is discussed in which device for asthma? The value of spacers is also discussed. It is not only the young who have poor coordination and various devices may be even more important for adults and the elderly. The use of nebulisers in General Practice is also discussed elsewhere.

For those who have very mild asthma, the occasional use of a beta agonist inhaler is probably all that is required. It may also suffice for exercise induced asthma but rather than using it when the wheezing starts, it is better to use it in anticipation, using in the changing room when getting ready for sport. For exercise induced asthma, both long acting beta agonists and leukotreine inhibitors are effective.⁸ For many people, exercise induced asthma may be an expression of poorly controlled asthma.⁹

The reader is referred to other texts for a full review of the stepwise approach to the management of asthma. The SIGN/BTS guidelines⁴ are evidence based and regularly updated. A few recent amendments are worthy of mention.

• It is suggested that a steroid inhaler may be introduced at an earlier stage than before and that the following may be reason to consider one:
  • Exacerbation of asthma in the last 2 years
  • Using inhaled beta-2 agonists three times a week or more
  • Symptomatic three times a week or more
• Long acting beta agonists should not be introduced unless the patient is already using a steroid inhaler.
• Patient education is extremely important. The patient must understand the disease and know when to change medication himself and when to call for help. This is included in the BTS/SIGN guidelines.⁴ Self management is beneficial to both the medical team and the patient.¹⁰

The management of asthma is a dynamic process involving stepping up medication if it deteriorates and stepping down when control has been achieved to use the least medication that keeps the patient well.

For those who have difficult asthma, the problem is often failure to comply with the regimens or poor inhaler technique.¹¹ Patients must be taught that using a steroid inhaler is not like taking steroid tablets in terms of risk of adverse effects. There is a great deal of evidence about management.¹²

• For children, inhaled corticosteroids are more beneficial than as-needed use of beta agonists, long-acting beta agonists, theophylline, cromolyn sodium, nedocromil, or any combination of those.
• Leukotriene modifiers are an alternative but not a preferred treatment. They should be considered if the medication needs to be administered orally rather than by inhaler.
• Cromolyn sodium and nedocromil are effective for long-term control, but they are not as effective as inhaled corticosteroids.
• Cromolyn sodium and nedocromil are alternatives, but not preferred treatments for mild persistent asthma.
• Cromolyn may be useful as a preventive therapy before exertion or unavoidable exposure to allergens.
• Regular inhalation of corticosteroids controls asthma significantly better than as-needed beta agonists.

Inadequate control of asthma leads to much morbidity and poor quality of life. There are around 74,000 emergency admissions to hospital for asthma in the UK each year and around 1,500 deaths. A common feature of deaths from asthma is that the patient and/or the medical staff have underestimated the severity of the attack. This is why it is essential to have objective criteria and why patients must be educated about their disease.

Many children with asthma will grow out of it but many will continue into adult life. Poor control of the disease will lead to irreversibility or COPD. This is especially likely in those who smoke.

It is not clear what has caused the increased prevalence of asthma and it is unclear how to avoid asthma. Allergy may be involved in some cases, especially occupational asthma. This may represent as much as 15% of adult asthma and if it is not recognised and treated appropriately, the prognosis is poor. Breast feeding is protective whilst maternal smoking seems to be a risk factor⁹ and anyone who has asthma is very foolish to smoke.

A confidential enquiry from the East of England concluded: In two-thirds of asthma deaths, medical management failed to comply with national guidelines. 'At-risk' asthma registers in primary care may improve recognition and management of 'at-risk' patients.¹³