Bronchial asthma is the most common chronic disease in industrialized nations, and there is every indication that its prevalence is increasing throughout the world. This disease accounts for a large proportion of health care spent and time lost from school and work. A lot of research has focused on the underlying mechanisms of asthma, which have important implications in therapy.
Asthma is characterized by three features
- Airway obstruction—which is reversible spontaneously or using drugs
- Airway inflammation
- Airway hyperresponsiveness.
It has now been proposed that bronchial asthma should be redefined as a chronic eosinophilic bronchitis.
Mechanism of Bronchial obstruction in Bronchial Asthma (Fig. 1.1)
Bronchoscopic Appearance of Bronchus (Fig. 1.2)
Atopic individuals are sensitized after exposure to allergens and develop lgE antibodies. Subsequent exposure to allergens causes a dual response which is protracted and more severe.
Thus bronchial asthma has two components (Box 1.1):
- ROAD (bronchospasm) which can be reversed with bronchodilators
- BHR due to inflammation (which predisposes patients to recurrent bronchospasms with minor stimuli like exercise, smoke, dust exposure, etc.). This is treated best with anti–inflammatory drugs such as corticosteroids.
Prevalence of Bronchial Asthma (Fig. 1.3)
There is a worldwide variation in the prevalence of asthma. It varies from country to country and in a country it varies from state to state. The largest study group which has conducted a study on prevalence of bronchial asthma is the ISAAC study group (International Study group on asthma and Allergic Disorders in children). They report a prevalence up to 25% (Lancet). Our own study at Ettumanoor Block area, Kottayam District and coastal areas of Kochi showed a prevalence of 22–25%.
Asthma is an iceberg disease. The classical features of bronchial asthma—that is, persistent cough, wheezing and dyspnea is seen in only 30% of children. The rest 70% of cases lie below iceberg. So there should be high index of suspicion to diagnose bronchial asthma in those children.
Any child presenting with persistent cough especially at 3 am to 4 am, one should suspect cough variant asthma (nocturnal asthma). They usually respond to bronchodilator. Any child presenting with cough after laughing, crying or exercise has an activity induced asthma. If a child presents with persistent cough after an episode of a viral AURI (acute upper respiratory infection), suspect bronchial asthma. Also children presenting with recurrent respiratory infection or recurrent pneumonia at different sites may have bronchial asthma.
- Routine blood counts may not help. Peripheral smear may show eosinophilia.
- X–ray chest may be normal or may show emphysematous changes or enhanced vascular marking. It helps to rule out tuberculosis.
- Sputum examination for eosinophils and Curschmann’s spirals.
- Pulmonary Function Test
- Peak expiratory flow rate (PEFR)
Peak Expiratory Flow Rate (PEFR)
A PEFR is the easiest and can be performed in children above 6 years. It is the fastest rate at which air can move through the airways during a forced expiration starting with fully inflated lungs. The PEFR correlates well with FEV1 (forced expiratory volume). Peak flow can be measured with the help of a peak flow meter (Fig. 1.4) which is a small, portable, convenient and inexpensive device. Ideally peak flow should be measured thrice a day but since this is practically difficult, twice a day monitoring should suffice—once in the morning and once at night.
The peak flow varies according to age, sex and height. An asthmatic’s normal peak flow should be within 20% of a person who is of the same age, height and sex, but who does not have asthma.
Typical Peak Flow Graph of an Asthmatic (Fig. 1.5)
The diurnal peak flow variation of a patient with asthma is more than 20%. An asthmatic’s peak flow graph shows wide fluctuations giving a ‘saw-toothed’ appearance.
Uses of PEFR Recording in Asthma
- Quick diagnosis and assessment of asthma;
- Measure the peak flow reading of the patient. Administer a bronchodilator to the patient, salbutamol 100 mcg2 puffs with a MDI or one inhalation of 200 mcg rotacap with a Rotahaler. Wait for 1520 minutes. Measure the peak flow of the patient again. If there is a 1520% increase in the peak flow when measured after administering a bronchodilator, it indicates a significant degree of reversible airway obstruction.
- Peak flow readings taken regularly can give a warning of an impending attack of bronchospasm before it starts. One can thus prevent it by stepping up the “preventer” therapy.
- Peak flow measured before and after treatment may show how effective the medicines are;
- Long-term follow up of asthma: ‘The personal best peak flow’ is the highest measurement that can be achieved in the middle of a good (asymptomatic) day after using inhaled bronchodilator.Using the personal best value is very useful for monitoring the disease regularly. Values persistently below 20 to 30% of the personal best would indicate worsening control of the disease.
- Diurnal variability is used for measuring control of asthma, particularly before discharge from hospital. If variability is more than 20%, discharge is not advisable.
Formula to find out normal PEFR
PEFR = (Height in cms − 100) x 5 + 100
Spirometry (Fig. 1.6)
Role of spirometry is limited in our set up. It is costly, cumbersome and is available in only few centers.
- Its role is limited in our set up.
- Costly, cumbersome and is available in only few centres.
A ratio of FEV1/FVC (Fig. 1.7) of less than 80% indicates airflow obstruction. Also, a reversibility in the absolute value of FEV1 by more than 20% after bronchodilators indicates a significantly reversible airflow obstruction.
(FEV1/FVC)% < 80% indicates airway obstruction.
Fig. 1.7: Recording during a forced vital capacity maneuver: A. In the normal person, and B. In the person with airway obstruction
Bronchial asthma has to be differentiated from a number of respiratory and non-respiratory conditions.
Consider asthma in all children whose presenting symptoms include:
- Recurrent cough
- Nocturnal cough
- Recurrent wheeze
- Recurrent breathlessness
- Recurrent lower respiratory tract infections
- Recurrent pneumonia in different lobes
- Exercise induced cough/ wheeze
Narrow down possible common causes based on age of onset of symptoms.