asthma

Introduction to Asthma

  • Updated clinical guidelines for asthma are developed and disseminated regularly.
  • Key organizations responsible for guidelines:
    • National Asthma Education and Prevention Program (NAEPP)
    • Global Initiative for Asthma (GINA)
  • Copyright © 2016 by Mosby, an imprint of Elsevier Inc.

National Asthma Education and Prevention Program (NAEPP)

  • First evidence-based asthma guidelines published in 1991.
  • Developed under the coordination of the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH).
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NAEPP Guidelines Structure

  • Today, the NAEPP guidelines are structured around four components:
    1. Assessment and monitoring of asthma
    2. Patient education
    3. Control of factors contributing to asthma severity
    4. Pharmacologic treatments
  • Copyright © 2016 by Mosby, an imprint of Elsevier Inc.

Global Initiative for Asthma (GINA)

  • Launched in 1993 in collaboration with:
    • NHLBI (NIH)
    • World Health Organization (WHO)
  • GINA's specific goals include:
    1. Increase awareness of asthma and public health consequences
    2. Promote identification of reasons for increased asthma prevalence
    3. Examine the association between asthma and the environment
    4. Reduce asthma morbidity and mortality
    5. Improve management of asthma
    6. Enhance availability and accessibility of effective asthma therapy
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Evidence-Based Management of Asthma

  • Resources from asthma experts globally have culminated in GINA providing an evidence-based, user-friendly program for asthma management.
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Anatomic Alterations of the Lungs in Asthma

  • Key alterations include:
    1. Smooth muscle constriction of bronchial airways (bronchospasm)
    2. Excessive production of thick, whitish bronchial secretions
    3. Mucous plugging
    4. Hyperinflation of alveoli (air trapping)
    5. In severe cases, atelectasis due to mucous plugging
    6. Bronchial wall inflammation leading to fibrosis, especially in severe cases due to remodeling
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Etiology and Epidemiology of Asthma

  • According to the CDC/NCHS:
    • Approximately 20.3 million adults (8.0%) in the U.S. have asthma.
    • About 4.7 million children (6.5%) have asthma.
    • Statistical estimation:
    • 1 in 10 children suffer from asthma.
    • 1 in 12 adults suffer from asthma.
    • Total estimated asthma sufferers in the U.S.: 24.9 million.
  • WHO estimates that about 262 million people globally have asthma.
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Risk Factors for Asthma

  • Risk factors categorized into two main types:
    1. Host factors
    2. Environmental factors
  • Environmental Factors:
    • Pollutants
    • Allergens
    • Smoking
  • Host Factors:
    • Genetics:
    • Production of IgE antibodies, airway hyperresponsiveness, inflammatory mediators, and T-helper cells.
    • Obesity:
    • Asthma is more prevalent in patients with obesity due to comorbidities and decreased lung function.
    • Sex:
    • In children under 14, asthma occurs more frequently in boys; severity peaks between ages 5-7.
    • In girls, asthma onset generally occurs at puberty; adults demonstrate a higher prevalence in females.
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Further Environmental and Other Risk Factors

  • Environmental Factors:
    • Allergens (outdoor and indoor air pollution)
    • Infections
    • Occupational sensitizers
    • Tobacco smoke
    • Diet
  • Other Risk Factors:
    • Drugs
    • Food additives and preservatives
    • Exercise-induced bronchoconstriction
    • Gastroesophageal reflux
    • Sleep-related asthma (nocturnal asthma)
    • Emotional stress
    • Perimenstrual asthma (catamenial asthma)
    • Allergic bronchopulmonary aspergillosis
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Pathophysiology of Asthma

  • Mechanisms leading to an asthma attack include:
    • Antigen exposure activates peripheral lymphoid tissues.
    • IgE production by sensitized mast cells.
    • Release of mediators such as histamine, leukotrienes, and prostaglandins leading to:
    • Smooth muscle constriction
    • Mucus hypersecretion
    • Dilation of blood vessels
    • Tissue edema
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Diagnosis of Asthma

  • Typical diagnostic signs include:
    1. Wheezing
    2. Recurrent cough
    3. Recurrent difficulty breathing
    4. Recurrent chest tightness
  • Symptoms exacerbated by:
    • Nighttime activity
    • Seasonal changes
    • Presence of eczema or family history of asthma/allergic diseases
    • Exposure to pets (especially with fur), aerosol chemicals, temperature changes, domestic dust mites, drugs, exercise, pollen, infections, smoke, and strong emotional experiences.
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Diagnostic and Monitoring Tests for Asthma

  • FEV1 (Forced Expiratory Volume in 1 second):
    • An increase of ≥ 12% (or ≥ 200 mL) after bronchodilator administration suggests reversible airflow limitation consistent with asthma.
  • FEV1/FVC (Forced Vital Capacity) Ratio:
    • A better measure of airflow limitation; normally greater than 0.75-0.80.
    • A value less than these indicates airflow limitation; asthma should be suspected.
  • Peak Expiratory Flow Rate (PEFR):
    • An improvement of 60 L/min (or ≥ 20% of pre-bronchodilator PEFR after bronchodilator inhalation) suggests a diagnosis of asthma.
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Other Diagnostic Tests for Asthma

  • FeNO (Fractional concentration of exhaled nitric oxide):
    • Normal values: <25 ppb for adults, <20 ppb for children.
    • A rise to over 50 ppb indicates inadequately managed asthma.
  • Radioallergosorbent test (RAST):
    • Positive skin test allergens increase the probability of asthma diagnosis.
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Challenges in Differential Diagnosis of Asthma

  • Specific challenges include:
    • Asthma diagnosis in children aged 5 years or younger.
    • Asthma diagnosis in older children and adults.
    • Differentiation of asthma from chronic obstructive pulmonary disease (COPD).
    • Cough-variant asthma, exercise-induced bronchoconstriction, occupational asthma, and sick building syndrome.
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Asthma, COPD, and Asthma-COPD Overlap Syndrome (ACOS)

  • Characteristics of ACOS include:
    • Age of onset usually over 40 years, symptoms may have begun in childhood.
    • Symptoms include persistent dyspnea with variability; however, airflow limitation is often not fully reversible.
  • Distinguishing Features of Asthma and COPD:
    • Asthma:
    • Onset typically before age 20.
    • Symptoms vary significantly over short periods, often worse at night or during early morning.
    • Patient history often includes prior asthma diagnosis and allergies.
    • COPD:
    • Onset generally after 40.
    • Persistent symptoms without treatment improvements, chronic cough/sputum precede dyspnea.
    • History of exposure to risk factors such as tobacco smoke.
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Cardiopulmonary Clinical Manifestations of Asthma

  • Clinical manifestations arise from pathophysiological mechanisms including bronchospasm and excessive bronchial secretions.
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Status Asthmaticus

  • Defined as a severe asthma episode unresponsive to standard pharmacologic therapy.
  • Patient may exhibit fatigue, decreasing ventilatory rate, progressive decrease in PaO2, and pH, with simultaneous increase in PaCO2 indicating acute ventilatory failure.
  • Noninvasive ventilatory assistance may be indicated, while continuous aerosolized bronchodilator therapy should also be provided.
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The Physical Examination in Asthma

  • Vital Signs:

    • Increased respiratory rate (tachypnea)
    • Increased heart rate
    • Increased blood pressure
    • Presence of pulsus paradoxus (decreased BP during inspiration, increased BP during expiration)

  • Physical Findings:

    • Use of accessory muscles during breathing
    • Pursed-lip breathing
    • Retractions in the intercostal region
    • Increased anteroposterior chest diameter (barrel chest)
    • Cyanosis
    • Cough and sputum production

  • Chest Assessment Findings:

    • Prolonged expiratory phase (I:E ratio > 1:3)
    • Decreased tactile and vocal fremitus
    • Hyperresonant percussion note
    • Diminished breath and heart sounds
    • Presence of wheezing and crackles

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Abnormal Laboratory Tests and Procedures in Asthma

  • Sputum Examination Findings:
    • Eosinophilia
    • Presence of Charcot-Leyden crystals
    • Mucus casts (Curschman spirals)
  • IgE Levels:
    • Elevated in cases of extrinsic asthma.
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Radiologic Findings in Asthma

  • Chest Radiograph Findings:
    • Increased anteroposterior diameter (suggestive of barrel chest)
    • Translucent (dark) lung fields
    • Depressed or flattened diaphragms
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General Management of Asthma

  • Primary goals of asthma management:
    1. Attain and maintain clinical control of asthma manifestations.
    2. Maintain normal activity levels, including exercise.
    3. Keep pulmonary function close to normal.
    4. Prevent asthma exacerbations.
    5. Avoid adverse effects from asthma medications.
    6. Prevent asthma-related mortality.
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Components of Asthma Management

  1. Develop Patient/Doctor Partnership:
    • Establish a partnership for self-management of asthma.
  2. Identify and Reduce Exposure to Risk Factors:
    • Patients should avoid or minimize exposure to asthma triggers.
  3. Assess, Treat, and Monitor Asthma:
    • A continuous cycle of assessment, treatment, and monitoring for asthma control.
  4. Manage Asthma Exacerbations:
    • Strategies for rapid relief of airflow obstruction and hypoxemia.
  5. Special Considerations:
    • Attention to unique conditions such as pregnancy, obesity, surgery, nasal and sinus issues, occupational asthma, and others.
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Management of Asthma Exacerbations

  • Initial Assessment:
    • History and vital signs, including use of accessory muscles and oxygen saturation.
  • Initial Treatment:
    • Administer oxygen to achieve O2 saturation of at least 90% (95% in children).
    • Continuous administration of inhaled rapid-acting β2-agonist.
    • Consider systemic glucocorticosteroids if no immediate response.
    • Reassess conditions after one hour.
  • Criteria for Moderate Episode:
    • PEFR 60-80% of predicted or personal best; moderate symptoms with accessory muscle use.
    • Treatment includes oxygen, inhaled β2-agonist, and oral glucocorticosteroids.
  • Criteria for Severe Episode:
    • PEFR <60% of predicted; severe symptoms with no improvement after initial treatment.
    • Treatment includes oxygen, inhaled β2-agonist and anticholinergic, systemic glucocorticosteroids, and possibly intravenous magnesium.
  • Monitoring Response:
    • Good response within 1-2 hours is marked by sustained improvement in PEFR and oxygen saturation.
    • In cases of inadequate response, admission to intensive care may be necessary.
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Special Considerations in Asthma Management

  • Integrated care considering:
    • Pregnancy
    • Comorbid conditions such as obesity and rhinitis
    • Surgical history
    • Occupational exposures and respiratory infections
    • Gastroesophageal reflux and aspirin-induced asthma
    • Anaphylaxis risk in asthmatic patients.
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