Asthma in Children

Asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma is a chronic inflammatory condition causing intermittent airway obstruction Airway obstruction Airway obstruction is a partial or complete blockage of the airways that impedes airflow. An airway obstruction can be classified as upper, central, or lower depending on location. Lower airway obstruction (LAO) is usually a manifestation of chronic disease, such as asthma or chronic obstructive pulmonary disease (COPD). Airway Obstruction, wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing, cough, and dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea. Genetics Genetics Genetics is the study of genes and their functions and behaviors. Basic Terms of Genetics and environmental factors play a significant role in etiology. A diagnosis of asthma in children often involves careful history taking, physical examination, pulmonary function tests, and radiologic studies to rule out other conditions. The goal is to minimize symptoms, exacerbations, and functional as well as psychological morbidity. Treatment also involves relief and chronic pharmacotherapy.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Introduction and Epidemiology

Definition

Asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma is defined as the episodic obstruction of lung airways resulting from a chronic inflammatory condition.

Classification

  • Based on natural course:
    • Recurrent wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing: caused by viral infections; usually resolves before patients are school-aged
    • Chronic asthma: allergy associated; usually persists into adulthood 
    • Asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma with declining lung function: associated with hyperinflation in childhood and male sex
  • Based on disease severity while not on asthma medication (see Table 1):
    • Intermittent
    • Persistent:
      • Mild
      • Moderate
      • Severe
  • Based on response to treatment (see Table 2):
    • Well controlled
    • Not well controlled
    • Very poorly controlled

Epidemiology

  • The most common chronic disease in childhood in developed countries
  • Prevalence in the US (017 years): approximately 9%
  • Among the most common causes of childhood emergency department visits, hospitalizations, and missed school days
  • 80% of all asthmatic patients report disease onset prior to 6 years of age, but only a minority have persistent asthma later in life.

Etiology and Pathophysiology

Etiology

  • A combination of genetic and environmental factors cause asthma
  • Genetic factors: > 100 gene associations (no monogenicity)
  • Environmental factors associated with asthma: 
    • Recurrent childhood wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing: common respiratory viruses such as rhinoviruses, respiratory syncytial virus Respiratory Syncytial Virus Respiratory syncytial virus (RSV) is an enveloped, single-stranded, linear, negative-sense RNA virus of the family Paramyxoviridae and the genus Orthopneumovirus. Two subtypes (A and B) are present in outbreaks, but type A causes more severe disease. Respiratory syncytial virus causes infections of the lungs and respiratory tract. Respiratory Syncytial Virus, adenovirus Adenovirus Adenovirus (member of the family Adenoviridae) is a nonenveloped, double-stranded DNA virus. Adenovirus is transmitted in a variety of ways, and it can have various presentations based on the site of entry. Presentation can include febrile pharyngitis, conjunctivitis, acute respiratory disease, atypical pneumonia, and gastroenteritis. Adenovirus, influenza virus Influenza virus Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza, parainfluenza virus Parainfluenza virus Human parainfluenza viruses (HPIVs) are single-stranded, linear, negative-sense RNA viruses of the family Paramyxoviridae and the genus Paramyxovirus. Human parainfluenza viruses are the 2nd most common cause of lower respiratory disease in children, after the respiratory syncytial virus. Parainfluenza Virus, and human metapneumovirus
    • Home allergens can initiate airway inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation in susceptible children.
  • Early childhood risk factors for persistent asthma:
    • Asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma in parents
    • Allergy including atopic dermatitis Atopic Dermatitis Atopic dermatitis, also known as eczema, is a chronic, relapsing, pruritic, inflammatory skin disease that occurs more frequently in children, although adults can also be affected. The condition is often associated with elevated serum levels of IgE and a personal or family history of atopy. Skin dryness, erythema, oozing, crusting, and lichenification are present. Atopic Dermatitis (Eczema), allergic rhinitis Rhinitis Rhinitis refers to inflammation of the nasal mucosa. The condition is classified into allergic, nonallergic, and infectious rhinitis. Allergic rhinitis is due to a type I hypersensitivity reaction. Non-allergic rhinitis is due to increased blood flow to the nasal mucosa. Infectious rhinitis is caused by an upper respiratory tract infection. Rhinitis, and food allergy
    • Severe lower respiratory tract infection such as pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia or bronchiolitis
    • Wheezing (not as a result of colds)
    • Male sex
    • Low birth weight 
    • Passive tobacco smoking
  • Asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma triggers: 
    • Allergens: 
      • Dust mites
      • Animal dander
      • Molds
      • Cockroaches
      • Seasonal pollens
      • Seasonal molds
    • Air pollutants:
      • Environmental tobacco smoke
      • Ozone
      • Nitrogen dioxide
      • Dust
      • Sulfur dioxide
    • Strong odors such as perfumes
    • Occupational/lifestyle exposures:
      • Farms and barns
      • Paint fumes
      • Cold, dry air
      • Physical exercise
      • Emotional stress
      • Hyperventilation
    • Comorbid conditions:
      • Rhinitis
      • Sinusitis Sinusitis Sinusitis refers to inflammation of the mucosal lining of the paranasal sinuses. The condition usually occurs concurrently with inflammation of the nasal mucosa (rhinitis), a condition known as rhinosinusitis. Acute sinusitis is due to an upper respiratory infection caused by a viral, bacterial, or fungal agent. Sinusitis
      • Gastroesophageal reflux
    • Drugs:
      • Beta blockers
      • Aspirin and nonsteroidal anti-inflammatory drugs

Pathophysiology

  • Complex interactions between the following 2 components lead to airway obstruction Airway obstruction Airway obstruction is a partial or complete blockage of the airways that impedes airflow. An airway obstruction can be classified as upper, central, or lower depending on location. Lower airway obstruction (LAO) is usually a manifestation of chronic disease, such as asthma or chronic obstructive pulmonary disease (COPD). Airway Obstruction:  
    • Increased smooth muscle tone
    • Airway inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation, edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema and exudate with eosinophils and other inflammatory cells such as neutrophils, monocytes, lymphocytes Lymphocytes Lymphocytes are heterogeneous WBCs involved in immune response. Lymphocytes develop from the bone marrow, starting from hematopoietic stem cells (HSCs) and progressing to common lymphoid progenitors (CLPs). B and T lymphocytes and natural killer (NK) cells arise from the lineage. Lymphocytes, mast cells, and basophils
  • Inflammation is mediated by helper T cells T cells T cells, also called T lymphocytes, are important components of the adaptive immune system. Production starts from the hematopoietic stem cells in the bone marrow, from which T-cell progenitor cells arise. These cells migrate to the thymus for further maturation. T Cells that produce proinflammatory cytokines (interleukin 4 [IL-4], IL-5, and IL-13) and chemokines.
  • Exposure to triggers and lack of appropriate therapy further induces a combination of the following (see image below)
    • Inflammation
    • Airway hypersensitivity response
    • Basement membrane thickening
    • Subepithelial collagen deposition and fibrosis
    • Smooth muscle hypertrophy
    • Mucus hypersecretion
Remodelling and pathological changes noted in asthma

Remodeling and pathological changes noted in asthma.

Image by Lecturio.

Clinical Presentation

History of chronic asthma

  • Most common symptoms: intermittent dry coughing and expiratory wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing
  • Other symptoms: 
    • Shortness of breath
    • Chest tightness
    • Chest pain Chest Pain Chest pain is one of the most common and challenging complaints that may present in an inpatient and outpatient setting. The differential diagnosis of chest pain is large and includes cardiac, gastrointestinal, pulmonary, musculoskeletal, and psychiatric etiologies. Chest Pain 
    • Self-imposed activity restrictions
    • General fatigue (possibly from poor sleep Sleep Sleep is a reversible phase of diminished responsiveness, motor activity, and metabolism. This process is a complex and dynamic phenomenon, occurring in 4-5 cycles a night, and generally divided into non-rapid eye movement (NREM) sleep and REM sleep stages. Physiology of Sleep)
    • Limited physical activity
    • Worsening of symptoms at night or with triggers (see above)
    • Improvement of symptoms with asthma medications Asthma medications Management of asthma aims to reduce symptoms and minimize future risks and adverse outcomes (hospitalizations, loss of lung function, etc.). Medications commonly utilized include inhalers that allow bronchodilation and inflammatory control. Biologic agents are available for severe asthma. Asthma Medications
    • Atopic dermatitis

Physical signs during exacerbations of asthma

  • Prolonged expiration with wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing
  • Decreased peripheral breath sounds
  • Rhonchi or occasional crackles may be heard due to excess mucus production
  • Segmental crackles + decreased breath sounds may indicate asthma-induced atelectasis Atelectasis Atelectasis is the partial or complete collapse of a part of the lung. Atelectasis is almost always a secondary phenomenon from conditions causing bronchial obstruction, external compression, surfactant deficiency, or scarring. Atelectasis or lobar pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
  • Peak expiratory flow in mild to moderate cases > 40%–70%
  • Severe exacerbations:
    • Respiratory distress
    • Suprasternal and intercostal retractions and nasal flaring
    • Expiratory and inspiratory wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing
    • Markedly decreased breath sounds
    • Peak expiratory flow < 40%
  • Signs of imminent respiratory arrest:
    • Drowsiness or confusion
    • Paradoxical thoracoabdominal movement
    • Bradycardia
    • Absent wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing
    • Peak expiratory flow < 25% (may not be required for evaluation)

Diagnosis

  • A diagnosis of asthma in children often involves a combination of careful history taking, physical examination, pulmonary function tests (usually feasible in children > 6 years), and radiologic studies to rule out other conditions. 
  • Spirometry findings consistent with asthma: 
    • Low forced expiratory volume in 1 second (FEV1) relative to predicted norms
    • FEV1:FVC (forced vital capacity) < 0.80
  • Main laboratory criteria consistent with asthma:
    • Reversibility in FEV1 with inhaled beta agonists by ≥ 12% or ≥ 200 mL
    • Worsening in FEV1 with exercise by ≥ 15%
    • Variation in peak flow (see Image 3) or FEV1 from day to day or AM to PM by ≥ 20% 
  • Chest X-ray: 
    • Typically normal in asthma
    • May show hyperinflation with flattening of the diaphragms during exacerbations or severe chronic asthma
    • Helps rule out other diagnoses such as aspiration pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia
    • Helps investigate complications such as atelectasis Atelectasis Atelectasis is the partial or complete collapse of a part of the lung. Atelectasis is almost always a secondary phenomenon from conditions causing bronchial obstruction, external compression, surfactant deficiency, or scarring. Atelectasis and pneumothorax Pneumothorax A pneumothorax is a life-threatening condition in which air collects in the pleural space, causing partial or full collapse of the lung. A pneumothorax can be traumatic or spontaneous. Patients present with a sudden onset of sharp chest pain, dyspnea, and diminished breath sounds on exam. Pneumothorax during asthma exacerbations
  • Chest computed tomography scan: further delineates comorbidities, differential diagnosis, and complications
  • Skin prick testing for allergen sensitization
  • Genetic testing: only for exclusion of monogenic obstructive lung diseases that could be misdiagnosed as asthma ( cystic fibrosis Cystic fibrosis Cystic fibrosis is an autosomal recessive disorder caused by mutations in the gene CFTR. The mutations lead to dysfunction of chloride channels, which results in hyperviscous mucus and the accumulation of secretions. Common presentations include chronic respiratory infections, failure to thrive, and pancreatic insufficiency. Cystic Fibrosis, primary ciliary dyskinesia Primary Ciliary Dyskinesia Primary ciliary dyskinesia (PCD), also known as immotile-cilia syndrome, is an autosomal recessive disorder leading to an impairment that affects mucociliary clearance. Primary ciliary dyskinesia is caused by defective ciliary function in the airways and is characterized by the loss of oscillation (immotility), abnormal oscillation (dyskinesia), or absence of cilia (aplasia). Primary Ciliary Dyskinesia), especially in patients with recurrent bronchitis and/or chronic productive cough

Management

The goal of asthma management is to prevent/minimize symptoms, exacerbations, and functional and psychological morbidity to provide a healthy lifestyle appropriate for the age of the child.

The management of asthma has 4 components:

  1. Continued assessment and monitoring (initially every 2–6 weeks, later every 1–6 months) made through an assessment of impairment and risk:
    • Impairment: frequency and intensity of symptoms and resulting functional limitations
    • Risk: likelihood of exacerbations, adverse events from medication, and long-term deterioration of lung function
  2. Education for self-management (includes exploiting nurses, pharmacists, clinics, schools, etc., in the education process):
    • Helping patients recognize their own level of control and signs of disease progression by peak-flow and/or symptom monitoring
    • Educating patients on environmental control, avoiding triggers and tobacco smoke, correct use of and adherence to medications, and difference between long-term and quick-relief medications
  3. Identification and management of precipitating factors and comorbidities:
    • Identifying allergens through skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin testing and counseling on avoidance strategies
    • Comorbidities may include bronchopulmonary aspergillosis Aspergillosis Aspergillosis is an opportunistic fungal infection caused by Aspergillus species, which are common spore-forming molds found in our environment. As Aspergillus species are opportunistic, they cause disease primarily in patients who are immunocompromised. The organs that are most commonly involved are the lungs and sinuses. Aspergillus/Aspergillosis, gastroesophageal reflux disease Gastroesophageal Reflux Disease Gastroesophageal reflux disease (GERD) occurs when the stomach acid frequently flows back into the esophagus. This backwash (acid reflux) can irritate the lining of the esophagus, causing symptoms such as retrosternal burning pain (heartburn). Gastroesophageal Reflux Disease, obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity, obstructive sleep apnea Obstructive sleep apnea Obstructive sleep apnea (OSA) is a disorder characterized by recurrent obstruction of the upper airway during sleep, causing hypoxia and fragmented sleep. Obstructive sleep apnea is due to a partial or complete collapse of the upper airway and is associated with snoring, restlessness, sleep interruption, and daytime somnolence. Obstructive Sleep Apnea, rhinitis Rhinitis Rhinitis refers to inflammation of the nasal mucosa. The condition is classified into allergic, nonallergic, and infectious rhinitis. Allergic rhinitis is due to a type I hypersensitivity reaction. Non-allergic rhinitis is due to increased blood flow to the nasal mucosa. Infectious rhinitis is caused by an upper respiratory tract infection. Rhinitis, sinusitis, depression, stress, low vitamin D levels.
    • Influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza vaccination Vaccination Vaccination is the administration of a substance to induce the immune system to develop protection against a disease. Unlike passive immunization, which involves the administration of pre-performed antibodies, active immunization constitutes the administration of a vaccine to stimulate the body to produce its own antibodies. Vaccination in all children > 6 months old with asthma
  4. Appropriate selection of medications:
    • A step-up approach in pharmacotherapy is recommended to control impairment and risk. Once controlled, a step-down approach is implemented to maintain control on the minimum amount of medication (see Table 1 and image below).
    • Before every step up: assessment of adherence, appropriate inhaler technique, and environmental control for avoidance of triggers/allergens
    • Inhalers are best given with a spacer device to maximize efficacy.
    • Asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma medications are used for relief and control.
    • Medications for relief:
      • Short-acting beta 2 agonists (SABA; e.g., albuterol)
      • Systemic corticosteroids
      • Short-acting muscarinic antagonist (SAMA; e.g., ipratropium)
    • Medications for control:
      • Inhaled corticosteroids
      • Long-acting beta 2 agonists (LABA; e.g., formoterol, salmeterol)
      • Theophylline
      • Leukotriene modifiers
      • Anti-immunoglobulin E (IgE) antibody (omalizumab)
      • IL-5 monoclonal antibodies Antibodies Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins (mepolizumab, benralizumab)
      • IL-4 receptor alpha monoclonal antibody (dupilumab)
      • Inhaled cromolyn or nedocromil (not available in the United States)
Table 1: Classification of asthma based on disease severity while not on asthma medication and the recommended action for treatment
Component of severity Classification of asthma severity
Intermittent Persistent
Mild Moderate Severe
Symptoms ≤ 2 days/week > 2 days/week Daily Throughout the day
SABA use ≤ 2 days/week > 2 days/week Daily Several times/day
Nighttime awakenings ≤ 2/month 3–4/month ≥ 1/week Nightly
Activity limitation None Minor Some Extreme
Lung function (only in children > 5 years)
  • Normal FEV1 between exacerbations
  • FEV1 ≥ 80%
  • FEV1/FVC > 85%
  • FEV1 60%–80%
  • FEV1/FVC > 80%
  • FEV1 60%–80%
  • FEV1/FVC 75%–80%
  • FEV1 < 60%
  • FEV1/FVC < 75%
Exacerbation requiring oral corticosteroid use 0–1 times/year ≥ 2 times/year
Recommended action for treatment Step 1 Step 2 Step 3 + medium-dose inhalded corticosteroids (ICS) Step 3 + medium-dose ICS, or Step 4 or 5
Consider a short course of oral corticosteroids.
In 2–6 weeks, evaluate for control and adjust dose accordingly.
Table 2: Classification of asthma control
Component of control Well controlled Not well controlled Very poorly controlled
Symptoms ≤ 2 days/week > 2 days/week or multiple times on ≤ 2 days/week Throughout the day
SABA use ≤ 2 days/week > 2 days/week or multiple times on ≤ 2 days/week Several times/day
Symptoms ≤ 2 days/week > 2 days/week Throughout the day
Nighttime awakenings ≤ 1/month ≥ 2/month ≥ 2/week
Activity limitation None Some Extreme
Lung function
FEV1 > 80% 60%–80% < 60%
FEV1/FVC > 80% 75%–80% < 75%
Exacerbation requiring oral corticosteroid use 0–1/year ≥ 2/year
Management of asthma in children

Step up ladder approach in management of asthma for children between 5-11. Note in children, long-acting bronchodilators are not used initially and the aim is to have lower doses of inhaled corticosteroids.

Image by Lecturio.

Acute Exacerbation of Asthma

Definition

Acute exacerbation of asthma is the acute or subacute progressive worsening of airway inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation and obstruction in an asthmatic patient.

General features

  • Often occurs at night, during sleep Sleep Sleep is a reversible phase of diminished responsiveness, motor activity, and metabolism. This process is a complex and dynamic phenomenon, occurring in 4-5 cycles a night, and generally divided into non-rapid eye movement (NREM) sleep and REM sleep stages. Physiology of Sleep
  • Decreased/absent response to SABA may result in a vicious cycle of shunting and further bronchoconstriction, leading to hypoxemia.
  • Exacerbations must be immediately assessed for severity (See table 3).

Management of acute exacerbations

  • At home:
    Parents/guardians must have a written action plan and act early to prevent further worsening of symptoms:
    • Repeat SABAs 3 times in 1 hour (appropriate response: resolution of symptoms in 1 hour and PEF > 80%).
    • Contact physician if further exacerbations within 24–48 hours.
    • Use short course of oral corticosteroids and contact physician if partial response.
    • Call 911 if any sign of severe and persistent symptoms.
    • Use of home epinephrine autoinjectors and portable oxygen therapy may be indicated in extreme cases.
  • Emergency department:
    • Goals:
      • Correct hypoxemia with oxygen therapy
      • Rapid reversal of airflow obstruction with repeated doses of SABA and early use of systemic corticosteroids + SAMA (inhaled ipratropium)
      • Consider adjunctive treatments, such as intravenous magnesium sulfate or heliox, in severe exacerbations unresponsive to treatment.
      • Prevent recurrence by intensification of therapy ± short-term systemic corticosteroid therapy.
    • Requirements for patients with persistent severe symptoms and high-flow oxygen requirements:
      • Laboratory evaluation with complete blood count, comprehensive metabolic panel, and arterial blood gases
      • Chest X-ray
      • Monitoring for dehydration
    • Patients with any signs of imminent respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure require endotracheal intubation and admission to a pediatric intensive care unit.
Table 3: Evaluation of severity — Clinical features during exacerbations of asthma based on severity
Mild Moderate Severe Respiratory arrest imminent
Alertness Normal Usually agitated Agitated Drowsy or confused
Respiratory rate (breaths/minute) Increased Increased > 30 Paradoxical thoracoabdominal movement or normal-low respiratory rate
Pulse (beats/minute) < 100 100–120 >120 Bradycardia
Wheeze End expiratory only Throughout expiration Throughout inhalation and expiration Absent
Inspiratory/expiratory ratio (normally 2:1) Inspiratory/expiratory ratio of 1:1 Inspiratory/expiratory ratio of 1:2 < 1:2 N/A
Accessory muscle use None Common Present Present, but decreasing
O2 saturation > 95% 90%–95% < 90% ± cyanosis < 90% ± cyanosis
PCO2 (mm Hg) < 42 < 42 < 42 < 42
Peak expiratory flow ≥ 70% 40%–69% 25%–39% ≤ 25%

Differential Diagnosis

  • Rhinosinusitis: difficult to diagnose in younger children due to absence of localized sinus pressure or tenderness; may be a comorbid condition 
  • Gastroesophageal reflux: can present with intermittent cough and wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing; may be a comorbid condition
  • Younger children:
    • Recurrent aspirations
    • Tracheobronchomalacia
    • Foreign-body aspiration
    • Bronchopulmonary dysplasia
    • Cystic fibrosis
    • Primary ciliary dyskinesia
  • Older children and adolescents:
    • Vocal cord dysfunction: may present with daytime wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing and stridor with coughing due to involuntary closure of vocal cords; spirometry and flexible rhinolaryngoscopy may confirm the diagnosis
    • Hypersensitivity pneumonitis Hypersensitivity Pneumonitis Hypersensitivity pneumonitis (HP), previously called extrinsic allergic alveolitis, is an immunologically induced inflammatory disease affecting the alveoli, bronchioles, and lung parenchyma. It is caused by repeated inhalation of an inciting agent in a susceptible host that triggers first a type III (complement-mediated) hypersensitivity reaction in the acute phase and then a type IV (delayed) reaction in the subacute and chronic phases. Hypersensitivity Pneumonitis in farms or bird-owner homes
    • Parasitic infestations or tuberculosis Tuberculosis Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis complex bacteria. The bacteria usually attack the lungs but can also damage other parts of the body. Approximately 30% of people around the world are infected with this pathogen, with the majority harboring a latent infection. Tuberculosis spreads through the air when a person with active pulmonary infection coughs or sneezes. Tuberculosis more commonly in rural developing countries
    • Chronic pulmonary disease, many of which may cause digital clubbing (absent in asthma)

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