Classification of Asthma

Classification of Asthma

Why do we classify asthma?

We classify asthma for the purpose of precise and efficient management. Aim of our management is not merely control of symptoms, but control of inflammation, since more inflammation in the airways is associated with more manifestation of disease, which demands more drugs to be prescribed.

How can we classify asthma?

A new classification is given by the Expert Panel-2 of National Asthma Education & Prevention Program, 1997, USA for better patient management.

It is based on frequency of symptoms, severity of attack and pulmonary function tests (PFT) abnormalities. According to this, asthma is classified into four groups.

1. Intermittent asthma - Between the attacks, patient is symptom free and PFT is normal.

2. Persistent asthma - Frequent attack i.e. patient has coughing, wheezing, or shortness of breath at night or early morning at least more than two occasion in a month. In between the attack patient may or may not be symptom free and PFT is abnormal except in mild persistent variety.

a) Mild Persistent Asthma: Usually patients have nocturnal attack of dyspnoea more than 2 times per month and baseline PEFR or FEV1 is usually

b) Moderate Persistent Asthma: Usually patients have almost daily attack of dyspnoea and baseline PEFR or FEV1 is

c) Severe Persistent Asthma: Usually patients have dyspnoea to some extent continuously for 6 months or more and baseline PEFR or FEV1 is less than 50% of predicted value.

3. Acute exacerbation : Loss of control of any class or variant of asthma, which may cause mild to life threatening attack.

a) Mild : Patient is dyspnoeic but can talk in sentences.

b) Moderate : Patients is more dyspnoeic and can not complete a sentences in one breath

c) Severe (status asthmaticus) : Patient is severely dyspnoeic, talks in words and may be restless, even unconscious.

4 Special Variants : 5 special types of asthma are described below :

a) Seasonal asthma : Some patients experience asthma symptoms only in relation to certain pollens and molds appearing in the environment during specific season.

Seasonal asthma should be treated according to the stepwise approach to long-term management of asthma. Anti-inflammatory therapy (inhaled corticosteroids, cromones) should be initiated daily prior to the anticipated onset of symptoms and continued through the season

b) Exercise Induced Asthma (EIA) : Exercise Induced Asthma or Exercise-induced bronchospasm is experienced by almost all asthma patients on exertion particularly during attack. But exercise may be the only precipitant of asthma symptoms for some patients. That is why it is a special variant of asthma. It is a bronchospastic event that is caused by loss of heat, water, or both from the lung during exercise because of hyperventilation of air that is cooler and dryer than that of the respiratory tree. Exercise Induced Asthma usually occurs during or few minutes after vigorous activity, reaches its peak 5 to 10 minutes after stopping the activity, and usually resolves in another 20 to 30 minutes.

A history of cough, shortness of breath, chest pain or tightness, wheezing, or endurance problems during exercise suggests Exercise Induced Asthma. An exercise challenge test can be used to establish the diagnosis.

To prevent EIA, normal dose of reliever inhaler (short acting b2 agonist) or cromolyn inhaler should be taken immediately before starting exercise. This will give 2-3 symptom free hours. These inhalers should be kept within reach during exercising. If any attack occurs, 2-4 puffs should be taken instantly. If the attack is severe, it should be repeated 5-10 minutes later. If the attack does not go away, emergency medical help should be sought.

c) Drug induced asthma : Some drugs, e.g. Aspirin may cause asthma symptoms to appear (1 in 30 cases). These drugs act by blocking cycloxygenase pathway of arachidonic acid metabolism. Thereby enhancing lypoxygenase pathway and producing leukotrienes to aggravate asthma symptoms. b-blocker drugs (Oral antihypertensives or even eye drops) such as Atenolol, Propanolol may also cause bronchospasm.

Avoidance of triggering drugs is mandatory in these cases. Analgesic of choice is Paracetamol. Selective COX-2 inhibitors can be used as a substitute. As it is not truly devoid of adverse reactions, it should be tested by oral challenge (i.e. 1/4th of oral dose, e.g. 25 mg of 150 mg nimosulide Tab.) in a controlled environment (i.e. in non-attack condition ) before prescribing.

d) Cough variant asthma : This variety presents with chronic cough and sputum eosinophilia, but without the abnormalities of airway function seen in asthma. Eosinophilic bronchitis is an alternative name of this variety. Cough variant asthma is seen especially in young children. Cough is the principal symptom. As cough frequently occurs at night, examinations during the day may be normal. Monitoring of morning and afternoon PEF variability and/or therapeutic trials with anti-inflammatory or bronchodilator medication may be helpful in diagnosis. Once the diagnosis is established, treatment should be according to the stepwise approach to long-term management of asthma.

For proper management, the following points must be considered:

Occupational asthma: Occupational asthma may be defined as asthma induced at work by exposure to occupation related agents, which are mainly inhaled at the workplace. The most characteristics feature in the medical history is symptoms improve on rest days or holidays. This type of asthma is mainly encountered in the following occupations.

All patients with suspected occupational asthma should have spirometry and assessment of response to bronchodilator. The most useful investigation is frequent serial peak expiratory flow monitoring. The keystone of effective management is cessation of further occupational exposure. If not possible, patients are managed following the step care asthma management plan.

Refractory Asthma

Definition: A subgroup of patients with asthma have more troublesome disease reflected by (1) high medication requirements to maintain good disease control or (2) persistent symptoms, asthma exacerbations, or airflow obstruction despite high medication use. This subgroup of asthmatic patients is termed as "Refractory Asthma". It encompasses the asthma subgroups previously described as "fatal asthma", "steroid-dependent and/or resistant asthma", "difficult to control asthma"," poorly controlled asthma"," brittle asthma", "unstable asthma" or "irreversible asthma".

Presentation: Clinically, patients with refractory asthma may present with a variety of separate and/or overlapping conditions. These may include:

  1. widely varying peak flows (Type-I Brittle asthma): > 40% diurnal variation of 50% of the time over a period of at least 150 days), despite considerable medical therapy including a dose of inhaled steroid of at least 1550 mcg of Beclomethasone or equivalent.
  2. severe, but chronic airflow limitation
  3. rapidly progressive loss of lung function (Type-II Brittle asthma): characterized by sudden acute attacks occurring in less than 3 hours without an obvious trigger on a background of apparent normal airway function or well controlled asthma.
  4. mucus production ranging from absent to copious
  5. varying responses to corticosteroids.

Diagnosis: A patient getting step-IV or V treatment with at least one of the following criteria may be categorized as suffering from refractory asthma:

  1. Asthma symptoms requiring short-acting b2-agonist use on a daily or near daily basis
  2. Persistent airway obstruction (FEV1 <80% of predicted value; diurnal PEFR variability >20%)
  3. One or more urgent care visits for asthma per year
  4. Three or more oral rescue steroid per year
  5. Prompt deterioration with < 25% reduction in oral or inhaled corticosteroid dose
  6. Near fatal asthma event in the past

This definition is applicable only to patients in whom - (1) other conditions have been excluded, (2) exacerbating factors have been optimally treated, and (3) poor adherence does not appear to be a confounding issue.

Management: While continuing step-IV or V treatment the following points should be considered in managing refractory asthma:

  1. Pitfalls of management.
  2. Intensive Patient Educating - Environmental control, Drug adherence, - Self management plan
  3. Home nebulisation - Continuous or as per need
  4. Vaccination - Flu, Measles and Pneumococcal vaccine
  5. Addition of Ipratropium, Leukotrienes antagonists and Disease modifying agents (may be helpful in some patients)

See Also:

Definition of Asthma

Etiology of Asthma

Diagnosis of Asthma

Investigation of Asthma

Medicines of Asthma

Further Reading:

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