Bronchial Asthma

Asthma is characterised by paroxysmal and reversible obstruction of the airways. It is increasingly understood as an inflammatory condition combined with bronchial hyper-responsiveness. Acute asthma involves:

• Bronchospasm (smooth muscle spasm narrowing airways)
• Excessive production of secretions (plugging airways)

Triggers unleash an inflammatory cascade within the bronchial tree leading to the typical symptoms of asthma e.g. wheeze, shortness of breath, chest tightness, cough. Even in asymptomatic periods, asthmatic lungs show evidence of inflammation compared to controls and there is much interest in how chronic or repeated episodes of inflammation may cause 'remodelling' of the airways and supporting vasculature leading to disease progression.¹

Acute severe asthma (status asthmaticus) can be life-threatening and the disease causes significant morbidity so it is imperative to treat energetically. The bulk of asthma management has taken place within primary care. Since 2004, it has been an important component of the Qualities and Outcomes Framework of the nGMS contract.²

• Undoubtedly, asthma is a very common condition and currently, according to Asthma UK:³
  • 5.2 million people in the UK receive treatment for asthma: 1 in 10 children and 1 in 12 adults.
  • It is the commonest chronic medical condition in children.
  • There are 4.1 million GP consultations for asthma per year.
  • The cost of asthma to the NHS runs at about a billion pounds per year.
• Internationally, the UK is one of the highest ranking countries in terms of asthma prevalence, hospital admissions and mortality.
• Peak prevalence occurs between 5 and 15, and falls thereafter until 55 to 64 years old when it starts to rise again.
• Gender differences - there is a male preponderance in childhood with a reversal in early adulthood.
• Certain trends in the prevalence of asthma seem apparent over time,⁴ but their interpretation is difficult, given methodological difficulties (variation in methods of data collection and classification) as well as cultural artefact from changes in the way patients describe respiratory symptoms and the 'ease' with which doctors apply the diagnosis.⁵
  • Asthma diagnoses have become much more common since the 1950s, with childhood prevalence increased by two to three times.
    The trend in childhood prevalence appears to have flattened or even fallen recently whilst it remains plateaued in adults.
  • Incidence (based on new asthma diagnoses from the GP) has risen in all ages to a plateau in the 1990s and subsequently fallen.
  • Hospital admission rates rose from the 1960s to the late 1980s and are now falling.
  • There was an asthma death 'epidemic' in the 1960s, particularly amongst children and young adults. This has been ascribed to treatment-related changes. A second, more gradual peak was seen in the 1970s-80s in adults and mortality has tended to decline since.

The numbers within an individual practice, based on an age/sex/disease register, tend to significantly overestimate true prevalence as many outgrow asthma without the removal of the diagnosis. It should be changed to past history of asthma when a patient is no longer receiving treatment for the condition.

Risk factors

There is a long list of possible risk factors but research is frequently contradictory or confounded:⁶

• Personal history of atopy⁷
• Family history of asthma or atopy⁷
• Inner city environment
• Socioeconomic deprivation
• Obesity⁸
• Prematurity and low birth weight
• Viral infections in early childhood
• Maternal smoking
• Smoking⁹
• Early exposure to broad spectrum antibiotics¹⁰

Possible protective factors include:

• Breast feeding¹¹
• Increasing sibship
• Growing up on a farm¹²

The history is extremely important as patients may present between acute attacks when examination and investigation may be completely normal. The paroxysmal nature of the condition is important.

Wheezing or rhonchi is seen as the cardinal feature but this can be misleading. Ensure that the patient or their parent/carer's understanding of 'wheeze' is the same as yours - whistling, squeaking or gasping sounds, or a different style, rate or timbre of breathing are all sometimes described as 'wheeze' so it is important to clarify. Also, wheeze can be absent in severe asthma when there is insufficient air flow to cause wheeze - beware the silent chest.

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

• Wheezing - common but not invariable
• Coughing
• Shortness of breath
• Chest tightness

Ask if there is an obvious precipitating or aggravating factor for attacks:

• Cold symptoms - URTI frequently trigger exacerbations.
• Cold air - if this causes chest pain in an adult, it may be angina.
• Exercise - symptoms may occur during exercise but more classically after exercise. Running is worse than cycling and it is uncommon swimming.
• Pollution - especially cigarette smoke.
• Allergens - exacerbations may occur seasonally around pollen exposure or following exposure to animals such as cats, dogs or horses.
• Time of day - 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.
• Work-related - if symptoms are better at home/during holidays, then asthma may be related to occupation. This has significant implications and it sensible 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 medication - the patient may have been started on a beta blocker recently (including drops for glaucoma) or taken anti-inflammatories. The association between NSAIDs, including aspirin, and the precipitation of asthma is well documented but in reality it is not often seen.
• Ask about smoking, including passive smoking.

Respiratory System, History and Examination, has been covered elsewhere. The chest should be examined but this may be normal between attacks.

• Before examining the chest, check the pulse rate. This may be artificially elevated by excessive use of beta₂-agonists but, nevertheless, tachycardia is a significant feature. Respiratory rates above 25/min and heart rate above 110/min are regarded as significant signs in adults.⁷ Where available, also check oxygen saturations in acute attacks (saturations of <92% indicate a more severe subgroup of patients who may require admission).
• Look at the patient's breathing:
  • Is it fast?
  • Is it laboured?
  • Do they appear anxious?
  • Can they speak in full sentences?
  • Are accessory muscles of respiration employed?
  • Is there pursed lip breathing?
  • Is there cyanosis?
• 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.
• With chronic asthma, there may be chest deformity e.g. Harrison's sulci.
• In a small child, there may be intercostal recession with respiratory distress.
• 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 and particularly if asymmetrical in a child, be suspicious of inhaled foreign body. There may be inspiratory ronchi too. Where 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.

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.
• Other congenital problems may present from birth or early in infancy e.g. laryngeal or tracheal structural abnormalities, congenital heart disease.
• Vomiting and aspiration in babies suggests gastro-oesophageal reflux which can cause a cough on lying down.
• Inhalation of a foreign body can occur at all ages from the orally-curious infant to the performing, older child catching peanuts or grapes in their mouth. Peanuts tend to go straight down to the right main bronchus and cause considerable inflammation and obstruct the right lower lobe. The choking episode may not have been observed by an adult or may have occurred sufficiently long ago for the family to have forgotten it.
• 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

• Chronic obstructive pulmonary disease (COPD) - reversibility 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. Diagnosing COPD is discussed elsewhere. Almost all patients with COPD do smoke or have smoked in the past. Asthmatics can also develop COPD. Whether or not this reflects disease progression or co-morbidity is debatable.
• Heart failure can cause nocturnal cough and cardiac asthma.
• Ischaemic heart disease - chest tightness or pain, especially on meeting a stiff wind on a cold morning, may be asthma or angina.
• Malignancy is important to remember, 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.
• Other less common causes of chronic cough, wheeze or breathlessness include pulmonary fibrosis, interstitial lung disease, recurrent pulmonary embolism and tuberculosis.

Distinguish wheezing from shortness of breath on exertion - this can be due to heart failure, severe anaemia and obesity, often aggravated by lack of physical fitness.

Peak flow

Measurement of peak expiratory flow rate (PEF) 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. Caution should be used when diagnosing asthma based on peak flow readings but it has an important role in the management of established asthma.
Lung function tests, whether peak flow or spirometry, are unreliable below the age of 5 and even among some older children and adults who lack comprehension or coordination for the task. As well as airways obstruction, poor effort or neuromuscular disease will limit performance. In those able to use a peak flow meter reliably, it is often helpful to prescribe a peak flow meter for home use to encourage self-monitoring and adjustment of treatment in line with a self-management plan.

Technique

• Peak flow is usually estimated with the patient standing, although results are not significantly different if the patient is seated.¹³
• Take in a deep breath and expel it as rapidly and as forcefully as possible into the meter.
• The very first part is all that matters for this test and it is not necessary to completely empty the lungs.
• Record the best of three tests. Continue blows if the two largest are not within 40 l/min as the patient is still acquiring the technique.

Interpretation

• 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 PEF increases with increasing height and it varies with age, reaching a peak in the early 20s and then gradually declining. Current normative charts are criticised for being outdated and not encompassing ethnic diversity.
• A patient's peak flow can be compared with that listed normal for their age, sex and height. However, it is often more helpful in an asthmatic to compare changes with an individual's best peak flow, recorded in a clinically stable period on optimal treatment. Thus a patient with asthma may have a "predicted" PEF of 500 l/min but know that a peak flow of 400 l/min indicates reasonable control but where it falls to 300 l/min that appropriate action is required.
• Patients are frequently asked to record a peak flow diary (recording PEF several times a day over a couple of weeks). It is normal for peak flow to fall slightly overnight and these 'nocturnal dips' may be accentuated in asthma. A marked diurnal variation in peak flow (>20%) 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. PEF is best recorded on a chart which provides graphical illustration of this variability. Peak flow variability is not specific to asthma and so its diagnostic value is debatable.⁷
• Reversibility testing can be performed with PEF testing in subjects with pre-existing airways obstruction and is demonstrated by an increase of >60 l/min.
• Peak flow diaries may also be helpful for patients with moderate or severe asthma. They can provide an objective warning of clinical deterioration.

Spirometry

• Spirometry is now preferred over peak flow measurement for initial confirmation of airways obstruction in the diagnosis of asthma as it is felt to offer clearer identification of airways obstruction, to be less effort dependent and more repeatable.⁷ Spirometry measures the whole volume that may be expelled in one breath (vital capacity). It also permits calculation of the percentage exhaled in the first second, called the FEV₁. However, as with peak flow, some (particularly young children) may not be able to reliably undertake it.
• Spirometry may be normal in individuals currently asymptomatic and does not exclude asthma and should be repeated, ideally when symptomatic. However, a normal spirogram when symptomatic does make asthma an unlikely diagnosis.
• It also offers good confirmation of reversibility in subjects with pre-existing airways obstruction where a change of >400 ml in FEV₁ is found after short-term bronchodilator/longer term corticosteroid therapy is trialled.

Chest x-ray

Chest x-ray is remarkably normal in even very severe asthma. It should not be used routinely in the assessment of asthma but consider CXR in any patient presenting with an atypical history or with atypical findings on examination.⁷

Diagnosis in adults

Current guidelines emphasise that the diagnosis of asthma is a clinical one, based on typical symptoms and signs, and a measurement of airflow obstruction for which spirometry is the preferred initial test. Ascribe high, intermediate or low probability of asthma based on this assessment to determine the use of further investigations or treatment trials.⁷

Where diagnosis is uncertain (intermediate probability) but with demonstration of airways obstruction (FEV₁/FVC < 0.7), reversibility testing and/or a trial of treatment is suggested. Adult patients with normal or near normal spirometry when symptomatic are likely to have non-pulmonary causes for their symptoms and these should be actively sought.⁷

Additional investigations of airways obstruction, responsiveness (e.g. histamine or methacholine provocation, exercise or inhaled mannitol challenges) or inflammation (e.g. induced sputum eosinophil count, exhaled nitric acid concentration) may be available through specialists and provide additional diagnostic support in difficult cases but their place in the diagnostic canon remains unclear.⁷

Diagnosis in children

Diagnosis in Children is difficult because of the complex nature of the disorder in the young and is dealt with elsewhere. Different 'phenotypes' of wheeze in children are identifiable only in retrospect - episodic viral-induced infant wheeze, some of which may persist/transform into atopic and non-atopic variants of childhood asthma. Also difficulties exist, particularly with younger children obtaining objective evidence of airways obstruction, where they cannot perform peak flow tests or spirometry.

See Acute severe asthma and status asthmaticus.

All patients with asthma in primary care should be reviewed at least annually and reviews should include:

• Symptomatic control assessment using a directed question-based tool. Even in practices with good resources, there is a great morbidity from inadequately controlled asthma.¹⁴ The Royal College of Physicians '3 questions' approach has been widely used and valued for its simplicity, although is poorly validated:
  • 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)?
  Alternatives include the Asthma Control Questionnaire, Asthma Control Test and Mini Asthma Quality of Life Questionnaire.
• Measurement and recording of lung function with peak flow or spirometry.
• Review of exacerbations in the last year, use of oral corticosteroids and time of school or work.
• Check inhaler technique.
• Check patient compliance and bronchodilator reliance. Review medication use - the use of more than 2 cannisters of reliever per month or 10-12 puffs per day - is associated with poorly controlled and higher risk asthma.
• Check patient ownership and use of an asthma action plan.

The stepwise approach

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 and need for rescue medication.
• Achieve best possible lung function (practically FEV₁ and/or PEF >80% predicted or best.
• 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. Maintain patients on the lowest possible dose of inhaled steroid. Reduce slowly, with reductions of 25-50%, every 3 months.
• Always check compliance with current medication, inhaler technique and exclude triggers as far as possible before starting a new drug.
• Patient education and access to a written personalised action plan is considered critical.

Devices

Delivery of drugs to the lungs is a very efficient method in terms of both swiftness of action and limitation of systemic side-effects. However, it is essential to ascertain that the patient is competent at using the inhaler. Simply giving a prescription for a MDI is inadequate: steps must be taken to teach the patient to use the device and to check technique. 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: not only the young have poor coordination, spacers may be just as important for adults and the elderly who have difficulties. The Use of Nebulisers in General Practice is also discussed elsewhere.

Drug treatment

Current UK guidelines advocate the following, stepwise drug management for adults:⁷

• Step 1 - for those with very mild, intermittent asthma, the occasional use of a beta₂-agonist inhaler may be all that is required but all patients with asthma should be prescribed this for short-term relief of symptoms as required.
• Step 2 - start regular inhaled steroid at an appropriate dose for the severity of disease (200-800 mcg/day beclometasone diproprionate or equivalent). Triggers for starting inhaled corticosteroids should be:
  • An exacerbation in the last 2 years.
  • Use of beta₂-agonist inhaler more than 3 times per week.
  • Symptomatic of asthma more than 3 times per week.
  • Waking due to asthma more than once per week.
• Step 3 - initial add on therapy involves the addition of a long-acting beta₂-agonist (LABA). These should not be used without the concurrent use of inhaled steroid. Where control is good, continue but where there is no response, stop and increase the dose of inhaled corticosteroid (up to 800 mcg/day beclometasone diproprionate or equivalent). With partial benefit, continue the LABA but also increase the inhaled corticosteroid dose. If this fails to provide control, trial a leukotriene receptor antagonist or SR theophylline.
• Step 4 - with persistent poor control, increase inhaled steroid up to 2000 mcg/day beclometasone diproprionate or equivalent and/or add a fourth drug (leukotriene receptor antagonist, SR theophylline or beta₂-agonist tablet).
• Step 5 - continuous or frequent use of oral steroids, maintaining high dose inhaled steroids.

Referral to a respiratory physician would be normal at step 4-5 depending on expertise.

Exercise induced asthma

For most, exercise-induced asthma indicates poorly controlled asthma and will require regular inhaled steroid treatment beyond the anticipatory use of a bronchodilator when preparing for sport. Where exercise poses a particular problem and patients are already on inhaled corticosteroids, consider the addition of long acting beta agonists, leukotriene inhibitors, chromones, oral beta₂-agonists or theophyllines.

Inadequate control of asthma leads to much morbidity and poor quality of life. 12.7 million working days per year are lost to asthma in the UK and there were 77,000 asthma-related emergency admissions in 2005.³
Complications mostly relate to acute exacerbations:

• Pneumonia
• Pneumothorax
• Pneumomediastinum
• Respiratory failure and arrest
• Death

Individuals continue to die from asthma (approximately 1,300 deaths in the UK from asthma in 2005³). A common feature of deaths from asthma is that the patient and/or the medical staff have underestimated the severity of the attack. Patients frequently have adverse psychosocial factors that interact with the ability to judge or manage their disease leading to late presentation. A confidential enquiry from the East of England concluded that in two-thirds of asthma deaths, medical management failed to comply with national guidelines. It is suggested that 'at-risk' asthma registers in primary care may improve recognition and management of high risk patients.^15,16

Many children will wheeze early in life (about 30% of the under 3s¹⁷) in response to respiratory tract infections but most appear to grow out of it by the time they go to school. A few will continue to wheeze and develop persistent or interval symptoms, similar to older children with atopic asthma. Predictors for continued wheezing include:⁷

• Presentation after 2 years old
• Male sex in prepubertal children
• Frequent or severe episodes of wheezing
• Personal or family history of atopy
• Abnormal lung function

Some children present with asthma later in childhood and they appear to be less likely to have markers of atopy early in life compared to the persistent early wheezers.¹⁸

In order to determine effective primary prevention strategies, we need to unpick the epidemiology of asthma, clearly identify risk and protective factors and come closer to an understanding of asthma's aetiology and changes in prevalence figures. It is striking how little we fully understand about what causes asthma. Whilst family history remains the strongest risk factor for developing atopic asthma, the interplay of the environment is far from clear. The "hygiene hypothesis" is currently popular: it suggests that decreased exposure to childhood infections, endotoxin and bacteria increases the risk of developing atopy.¹⁹ Current guidelines suggest the promotion of breastfeeding (for its other benefits and possible preventative effect) and smoking cessation amongst parents, but evidence for other strategies (e.g.modifying maternal diet during pregnancy, weaning strategies or early aeroallergen avoidance) is lacking.⁷