childhood asthma

Bronchial asthma in children

Prof.Dr. Muhi K. Aljanabi
MRCPCH; DCH; FICMS
Consultant Pediatric Pulmonologist
Objectives
Understand the natural history of asthma during childhood.
Module Objectives
Outcome 1: 8. The graduate will be able to apply to medical practice biomedical scientific principles, method and knowledge and be able to:
Outcome 1: 8.(a) Explain normal human structure and functions from infancy through to adulthood.
Outcome 1: 8.(b) Explain the scientific bases for common disease presentations in childhood.
Be familiar with the key features of history and examination that support a diagnosis of asthma.
Module Objectives
Outcome 1: 8.(b) Explain the scientific bases for common disease presentations in childhood.
Outcome 2: 13 (a) Take and record a medical history, including family and social history, talking to parents or other carers where appropriate.
Outcome 2: 13 (c) Perform a full physical examination in an infant and child.
Be familiar with the other common clinical conditions that can mimic asthma (gastroesophageal reflux, cystic fibrosis, viral induced wheezing, bronchiolitis, and croup).
Module Objectives
Outcome 1: 8.(b) Explain the scientific bases for common disease presentations in childhood.
Be able to manage an acute exacerbation of asthma.
Module Objectives
Outcome 1: 8.(e) Select appropriate forms of management for common childhood diseases, and ways of preventing common diseases, and explain their modes of action and their risks from first principles.
Outcome 2: 14 (g) Formulate a plan for treatment, management and discharge, according to established priciples and best evidence, in partnership with the child, their carers, and other health professionals as appropriate. Respond to patients' concerns and preferences, obtain informed consent, and respect the rights of patients to reach decisions with their doctor about their treatment and care and to refuse or limit treatment.
Outcome 2: 16 (a) Assess and recognise the severity of a clinical presentation and a need for immediate emergency care in relation to infants and children.
Outcome 2: 16 (b) Diagnose acute medical emergencies in relation to infants and children.
Know the details of the drugs used to treat acute and chronic asthma and understand their mechanism of action.
Module Objectives
Outcome 1: 8.(f) Demonstrate knowledge of drug actions: therapeutics and pharmacokinetics; drug side effects and interactions, including for multiple treatments, longterm conditions and non-prescribed medication; and also including effects on the population, such as the spread of antibiotic resistance.
Outcome 2: 17 (b) Plan appropriate drug therapy for common indications, including pain and distress.
Outcome 2: 17 (e) Provide patients with appropriate information about medicinces
Outcome 2: 17 (f) Access reliable information about medicines.
Know the guidelines for the management of asthma.
Module Objectives
Outcome 1: 8.(e) Select appropriate forms of management for common childhood diseases, and ways of preventing common diseases, and explain their modes of action and their risks from first principles.
Outcome 2: 14 (g) Formulate a plan for treatment, management and discharge, according to established priciples and best evidence, in partnership with the child, their carers, and other health professionals as appropriate. Respond to patients' concerns and preferences, obtain informed consent, and respect the rights of patients to reach decisions with their doctor about their treatment and care and to refuse or limit treatment.
Be able to assess asthma control during childhood.
Module Objectives
Outcome 1: 8.(b) Explain the scientific bases for common disease presentations in childhood.
Outcome 1: 9.(b) Discuss psychological concepts of health, illness and disease.
Outcome 1: 9. (e) Discuss psychological aspects of behavioural change and treatment compliance.
Be able to advise parents about how to care for a child with asthma.
Asthma is a chronic inflammatory condition of the lung airways resulting in episodic airflow obstruction. This chronic inflammation heightens the “twitchiness” of the airways—airways hyperresponsiveness (AHR)—to provocative exposures.
ETIOLOGY:
More than 22 loci on 15 autosomal chromosomes have been linked to asthma.
Viral infections of the airways manifesting as pneumonia or bronchiolitis requiring hospitalization are risk factors for persistent asthma in childhood.
Indoor and home allergen exposures in sensitized individuals can initiate airways inflammation and hypersensitivity to other irritant exposures, and are strongly linked to disease severity and persistence. Environmental tobacco smoke and air pollutants (ozone, sulfur dioxide) aggravate airways inflammation and increase asthma severity.
Cold dry air and strong odors can trigger bronchoconstriction when airways are irritated.
EPIDEMIOLOGY:
Asthma is a common chronic disease, causing considerable morbidity.
Worldwide, childhood asthma appears to be increasing in prevalence, despite considerable improvements in management.
A large international survey study of childhood asthma prevalence found a wide range in asthma prevalence, from 1.6 to 36.8%.
Approximately 80% of all asthmatics report disease onset prior to 6 yr of age.
Of all young children who experience recurrent wheezing, however, only a minority will go on to have persistent asthma in later childhood.


CLINICAL MANIFESTATIONS AND DIAGNOSIS:

Intermittent dry coughing and/or expiratory wheezing are the most common chronic symptoms of asthma.
Older children and adults will report associated shortness of breath and chest tightness; younger children are more likely to report intermittent, nonfocal chest “pain.”
Respiratory symptoms can be worse at night, especially during prolonged exacerbations triggered by respiratory infections or inhalant allergens.
Daytime symptoms, often linked with physical activities or play, are reported with greatest frequency in children.
Other asthma symptoms in children can be subtle and nonspecific, including self-imposed limitation of physical activities, general fatigue (possibly due to sleep disturbance), and difficulty keeping up with peers in physical activities.
Asking about previous experience with asthma medications (bronchodilators) may provide a history of symptomatic improvement with treatment that supports the diagnosis of asthma.
Lack of improvement with bronchodilator and corticosteroid therapy is inconsistent with underlying asthma and should prompt more vigorous consideration of asthma-masquerading conditions.
Asthma symptoms can be triggered by numerous common events or exposures: physical exertion and hyperventilation (laughing), cold or dry air, and airways irritants.
The presence of risk factors, such as a history of other allergic conditions (allergic rhinitis, allergic conjunctivitis, atopic dermatitis, food allergies), parental asthma, and/or symptoms apart from colds, supports the diagnosis of asthma.
During routine clinic visits, children with asthma commonly present without abnormal signs, which stresses the importance of the medical history in diagnosing asthma.
Some may exhibit a dry, persistent cough.
The chest examination is often normal.
Deeper breaths can sometimes elicit otherwise undetectable wheezing.
In clinic, quick resolution (within 10 min) or convincing improvement in symptoms and signs of asthma with administration of a short-acting inhaled beta-agonist is supportive of the diagnosis of asthma.

LABORATORY FINDINGS:

Lung function tests can help to confirm the diagnosis of asthma and determine disease severity.
Chest radiographs (posteroanterior and lateral views) in children with asthma often appear to be normal, aside from subtle and nonspecific findings of hyperinflation (flattening of the diaphragms) and peribronchial thickening.
Chest radiographs can be helpful in identifying abnormalities that are hallmarks of asthma masqueraders (aspiration pneumonitis, hyperlucent lung fields in bronchiolitis obliterans), and complications during asthma exacerbations (atelectasis, pneumomediastinum, pneumothorax).
Some lung abnormalities can be better appreciated with high-resolution, thin-section chest CT scans. Bronchiectasis is sometimes difficult to appreciate on chest radiograph, but is clearly seen on CT scan and implicates an asthma masquerader such as cystic fibrosis, allergic bronchopulmonary mycoses (aspergillosis), ciliary dyskinesias, or immune deficiencies.
Other tests, such as allergy testing to assess sensitization to inhalant allergens, help with the management and prognosis of asthma.
TREATMENT:
Principles of Asthma Pharmacotherapy:


A major objective of this approach is to identify and treat all “persistent” asthma with anti-inflammatory controller medication.
The “three strikes” rule is a handy memory aid for determining if an asthmatic child should receive controller therapy. Simply put, if an asthmatic child has asthma symptoms or uses quick-relief medication at least 3 times per wk, awakens at night due to asthma at least 3 times per mo, requires a refill for a quick-relief inhaler prescription at least 3 times per yr, experiences asthma exacerbations at least 3 times per yr, or requires short courses of systemic corticosteroids at least 3 times a yr, then that patient should receive daily controller therapy.

Inhaled corticosteroid (ICS) therapy is recommended as preferred therapy for all levels of asthma severity except for the mild intermittent category.
Leukotriene pathway modifiers or sustained-release theophylline (only for patients >5 yr of age) are considered alternative controllers for mild persistent asthmatics.
Combination therapy of a low-to-medium dose ICS with a long-acting β-agonist (LABA; preferred) or a leukotriene modifier or theophylline is a mainstay therapy for moderate persistent asthma in older children and adults.
While the use of medium-dose ICS alone is an alternative therapy for older children and adults with moderate persistent severity, for infants and young children, it is considered a preferred treatment for moderate persistent asthma.
Severe persistent asthmatics should receive high-dose ICS, a long-acting bronchodilator, and routine oral corticosteroids if needed.
Daily controller therapy is not recommended for mild intermittent asthma.
SABAs are the recommended quick-reliever medications for symptoms and exercise pretreatment for all asthma severity levels.

INHALED CORTICOSTEROIDS (ICS):

Daily ICS therapy as the treatment of choice for all patients with persistent asthma. ICS therapy has been shown to reduce asthma symptoms, improve lung function, reduce AHR, reduce “rescue” medication use and, most important, reduce urgent care visits, hospitalizations, and prednisone use for asthma exacerbations by about 50%. ICS therapy may lower the risk of death due to asthma. It can achieve all of the goals of asthma management and, as a result, is viewed as first-line treatment for persistent asthma.

The most commonly encountered adverse effects from ICSs are local: oral candidiasis (thrush) and dysphonia (hoarse voice). Thrush results from propellant-induced mucosal irritation and local immunosuppression. Dysphonia occurs from vocal cord myopathy. These effects are dose-dependent and are most common in individuals on high-dose ICS and/or oral cortico-steroid therapy. The incidence of these local effects can be greatly minimized by using a spacer with MDI ICS because spacers reduce oropharyngeal deposition of the drug and propellant. Mouth rinsing using a “swish and spit” technique after ICS use is also recommended.

LONG-ACTING INHALED β-AGONIST (LABA).

Although LABAs (salmeterol, formoterol) are β-agonists, they are considered to be daily controller medications, not intended for use as “rescue” medication for acute asthma symptoms or exacerbations, nor as monotherapy for persistent asthma. Salmeterol has a prolonged onset of action, with maximal bronchodilation about 1 hr after administration, whereas formoterol has an onset of action within 5–10 min. Both medications have a prolonged duration of effect of at least 12 hr. Given their long duration of action, they are well suited for patients with nocturnal asthma and for individuals who require frequent SABA use during the day to prevent exercise-induced bronchospasm. Their major role is as an “add-on” agent in patients who are suboptimally controlled on ICS therapy alone. For those patients, several studies have found the addition of LABA to ICS to be superior to doubling the dose of ICS, especially on day and nocturnal symptoms. There are also controller formulations that combine ICS with LABA (fluticasone/salmeterol, budesonide/formoterol).
LEUKOTRIENE-MODIFYING AGENTS:
Both montelukast and zafirlukast improve asthma symptoms, decrease need for rescue β-agonist use, and improve lung function. Montelukast, which is used in children ≥1 yr of age, is administered once daily. Zafirlukast is used in children ≥5 yr of age and is administered twice daily. LTRAs appear to be less effective than ICSs in patients with moderate persistent asthma.
In general, ICS improves lung function by 5–15%, whereas LTRA improves lung function by 2–7.5%.


NONSTEROIDAL ANTI-INFLAMMATORY AGENTS:
Cromolyn and nedocromil are non-corticosteroid anti-inflammatory agents that can inhibit allergen-induced asthmatic responses and reduce exercise-induced bronchospasm. Both drugs are considered alternative anti-inflammatory drugs for children with mild persistent asthma. Although largely devoid of adverse effects, these medications must be administered frequently (2–4 times/day) and are not nearly as effective daily controller medications as ICSs and leukotriene-modifying agents. Because they inhibit exercise-induced bronchospasm, they can be used in place of SABAs, especially in children who develop unwanted adverse effects with β-agonist therapy (tremor and elevated heart rate). They can also be used in addition to a SABA as a combination pretreatment for exercise-induced bronchospasm in patients who continue to experience symptoms despite SABA pretreatment alone.
THEOPHYLLINE:
In addition to its bronchodilator effects, theophylline has anti-inflammatory properties as a phosphodiesterase inhibitor, although the extent of their clinical relevance has not been clearly established. Theophylline, when used chronically, can reduce asthma symptoms and the need for rescue SABA use. Although it is considered an alternative monotherapy controller agent for older children and adults with mild persistent asthma, it is no longer considered a first-line agent for small children in whom there is significant variability in the absorption and metabolism of different theophylline preparations, necessitating frequent dose monitoring (blood levels) and adjustments.. Theophylline overdosage and elevated theophylline levels have been associated with headaches, vomiting, cardiac arrhythmias, seizures, and death.

SHORT-ACTING INHALED β-AGONISTS (SABA):

Given their rapid onset of action, effectiveness, and 4–6 hr duration of action, SABAs (albuterol, , terbutaline) are the first drugs of choice for acute asthma symptoms (“rescue” medication) and for preventing exercise-induced bronchospasm. Β-Agonists bronchodilate by inducing airway smooth muscle relaxation, reducing vascular permeability, reducing airways edema, and improving mucociliary clearance.
ANTICHOLINERGIC AGENTS:
As bronchodilators, the anticholinergic agents (ipratropium bromide) are much less potent than the β-agonists. Inhaled ipratropium is primarily used in the treatment of acute severe asthma. When used in combination with albuterol, ipratropium can improve lung function and reduce the rate of hospitalization in children who present to the emergency department with acute asthma. It is approved for children >12 yr of age.

Asthma exacerbations and their Management:

Asthma exacerbations are acute or subacute episodes of progressively worsening symptoms and airflow obstruction. Airflow obstruction during exacerbations can become extensive, resulting in life-threatening respiratory insufficiency.
Often, asthma exacerbations worsen during sleep (between midnight and 8 am) when airways inflammation and hyperresponsiveness are at their peak.
Importantly, SABAs, which are first-line therapy for asthma symptoms and exacerbations, increase pulmonary blood flow through obstructed, unoxygenated areas of the lungs with increasing dosage and frequency.
When airways obstruction is not resolved with SABA use, ventilation-perfusion mismatching can cause significant hypoxemia, which can perpetuate bronchoconstriction and further worsen the condition.
Severe, progressive asthma exacerbations need to be managed in a medical setting, with administration of supplemental oxygen as first-line therapy and close monitoring for potential worsening.
Complications that can occur during severe exacerbations include atelectasis and air leaks in the chest (pneumomediastinum, pneumothorax).
A severe exacerbation of asthma that does not improve with standard therapy is termed status asthmaticus.

Home Management of Asthma Exacerbations:

Early recognition of asthma exacerbations in order to intensify treatment early can often prevent further worsening and keep exacerbations from becoming severe.
A written home action plan can reduce the risk of asthma death by 70%.
Immediate treatment with “rescue” medication (inhaled SABA, up to 3 treatments in 1 hr) is recommended.
A good response is characterized by resolution of symptoms within 1 hr, no further symptoms over the next 4 hr, and improvement in PEF to at least 80% of personal best.
The child's physician should be contacted for follow-up, especially if bronchodilators are required repeatedly over the next 24–48 hr.

If the child has an incomplete response to initial treatment with rescue medication (persistent symptoms and/or a PEF <80% of personal best), a short course of oral corticosteroid therapy (prednisone 1–2 mg/kg/day [not to exceed 60 mg/day] for 4 days) in addition to inhaled β-agonist therapy should be instituted. The physician should also be contacted for further instructions.
Immediate medical attention should be sought for severe exacerbations, persistent signs of respiratory distress, lack of expected response or sustained improvement after initial treatment, further deterioration, or high-risk factors for asthma morbidity or mortality (previous history of severe exacerbations).
For patients with severe asthma and/or a history of life-threatening episodes, especially if abrupt-onset in nature, providing an injectable forms of epinephrine and possibly portable oxygen at home should be considered.
Use of either of these extreme measures for home management of asthma exacerbations would be an indication to call for emergency support services.

Emergency Department Management of Asthma Exacerbations:

In the emergency department, the primary goals of asthma management include correction of hypoxemia, rapid improvement of airflow obstruction, and prevention of progression or recurrence of symptoms.
Indications of a severe exacerbation include breathlessness, dyspnea, retractions, accessory muscle use, tachypnea or labored breathing cyanosis, mental status changes, a silent chest with poor air exchange, and severe airflow limitation (PEF or FEV1 <50% of personal best or predicted values).
Initial treatment includes supplemental oxygen, inhaled β-agonist every 20 min for 1 hr, and, if necessary, systemic corticosteroids given either orally or intravenously.
Inhaled ipratropium may be added to the β-agonist treatment if no significant response is seen with the 1st inhaled β-agonist treatment.
An intramuscular injection of epinephrine or other β-agonist may be administered in severe cases.
Oxygen should be administered and continued for at least 20 min after the last injection to compensate for possible ventilation-perfusion abnormalities caused by SABAs.
Close monitoring of clinical status, hydration, and oxygenation are essential elements of immediate management.
A poor response to intensified treatment in the 1st hour suggests that the exacerbation will not remit quickly.
The patient may be discharged to home if there is sustained improvement in symptoms, normal physical findings, PEF >70% of predicted or personal best, an oxygen saturation >92% on room air for 4 hr.
Discharge medications include administration of an inhaled β-agonist up to every 3–4 hr plus a 3–7 day course of an oral corticosteroid.
Optimizing controller therapy before discharge is also recommended.
The addition of ICS to a course of oral corticosteroid in the emergency department setting reduces the risk of exacerbation recurrence over the subsequent month.
Rarely, a severe asthma exacerbation in children results in respiratory failure, and intubation and mechanical ventilation become necessary.


PROGNOSIS:

Recurrent coughing and wheezing occurs in 35% of pre–school-age children.

Of these, ⅓ continue to have persistent asthma into later childhood,
while ⅔ improve on their own through the preteen years.
Asthma severity by the ages of 7–10 yr of age is predictive of asthma persistence in adulthood.
Children with moderate to severe asthma and with lower lung function measures are likely to have persistent asthma as adults.
Children with milder asthma and normal lung function are likely to improve over time.