Clinical Case: Asthma

Presenting Case

Physical Examination

Pathophysiology

1. Atopic (Allergic) Asthma - Immunologic Mechanism

• Early-phase reaction (0-1 hour): Allergen crosslinks IgE on mast cells, causing degranulation and release of:
  • Histamine - causes bronchospasm and mucosal edema
  • Prostaglandin D2 - bronchoconstriction
  • Leukotrienes C4, D4, E4 - potent bronchoconstrictors and promoters of mucus secretion
  • Reflex neural pathway activation also contributes to bronchoconstriction
• Late-phase reaction (4-12 hours): Inflammatory mediators stimulate epithelial cells to produce chemokines (including eotaxin), recruiting eosinophils and other inflammatory cells. Th2 cytokines sustain airway inflammation.

2. Nonatopic Asthma

3. Airway Remodeling

• Subbasement membrane thickening
• Hypertrophy of bronchial smooth muscle and glands
• Goblet cell metaplasia - excessive mucus production
• These changes may add an irreversible component to airway obstruction over time

Although bronchospasm is a key component of reversible obstruction, current guidelines emphasize the inflammatory pathophysiology of asthma. The clinician must treat and prevent the inflammation that leads to mucosal edema, secretions, histologic remodeling of the airways, and smooth muscle bronchospasm. - Textbook of Family Medicine 9e

Triggers in This Patient

Investigations

Spirometry (key investigation)

Peak Expiratory Flow Rate (PEFR)

• Reduced baseline; diurnal variation >20% is characteristic
• Best respiratory parameter for ongoing monitoring and exacerbation assessment

Additional Investigations

• Total IgE: Elevated (atopic pattern)
• Blood eosinophilia: May be present (>4% suggests atopic sensitization)
• Skin prick testing / RAST: Positive to cat dander, house dust mite, grass pollen
• CXR: Usually normal or shows hyperinflation; useful to exclude pneumothorax during acute exacerbations
• ABG (if severe): Mild hypoxemia + respiratory alkalosis; normalization of PCO2 without clinical improvement signals impending respiratory failure

Diagnosis

NAEPP Classification (≥12 years)

Differential Diagnosis to Exclude

Management

Long-Term Stepwise Management (NAEPP Step 3 - Moderate Persistent)

• Low-dose ICS + LABA (preferred) - e.g., fluticasone/salmeterol
• OR medium-dose ICS alone
• SABA (albuterol) for rescue

All patients with persistent asthma (daytime symptoms >2x/week or nocturnal symptoms >2x/month) should be treated with daily long-term control medication, preferably an inhaled corticosteroid (ICS). - Textbook of Family Medicine 9e

Key Drug Classes

Non-Pharmacologic / Environmental Measures

• Eliminate exposure to cat allergen (most important immediate change for this patient)
• HEPA air filtration, allergen-proof mattress/pillow covers
• Eliminating passive smoke exposure is the single most important trigger control intervention
• Treat comorbid allergic rhinitis (intranasal steroids ± antihistamine)
• Influenza vaccination annually
• Written asthma action plan with peak flow monitoring

Self-Management Education

• Teach correct MDI technique with spacer (spacers are as effective as - or better than - nebulizers for acute attacks)
• Peak flow diary to identify early deterioration
• Identify and avoid personal triggers
• Know when to escalate care / go to ED

Acute Exacerbation Management

Severity Assessment

Emergency Treatment Protocol

1. SABA (salbutamol/albuterol) - repeated doses via nebulizer or MDI+spacer (every 20 min x 3 in first hour)
2. Ipratropium bromide - combined with SABA at initiation; reduces hospitalization rate (benefit does not persist after admission)
3. Systemic corticosteroids (IV methylprednisolone or oral prednisolone) - "unequivocally associated with a more rapid return to baseline function; first-line for acute exacerbations" - Murray & Nadel's
4. Supplemental oxygen - target SpO2 93-95%
5. IV Magnesium sulfate - in severe/refractory cases; inhibits smooth muscle contraction and acetylcholine release
6. ICU/intubation - if PCO2 normalizes without clinical improvement (impending respiratory failure), progressive exhaustion, or GCS decline

• Previous near-fatal asthma / prior ICU admission
• Overuse of SABAs or underuse of ICS
• Recent oral corticosteroid course
• Comorbid psychiatric disease
• Poor perception of airflow limitation

Follow-Up and Monitoring

Complications

• Acute: Status asthmaticus, respiratory failure, pneumothorax (from air-trapping)
• Chronic: Airway remodeling with fixed obstruction, exercise intolerance, nocturnal sleep disruption, reduced quality of life
• Occupational impact: ATS impairment rating used for medicolegal assessment (post-bronchodilator FEV1, degree of airway hyperresponsiveness, minimum medication need)
• Special population: In pregnancy, moderate-to-severe asthma increases risk of preterm labor, low birth weight, perinatal death, and pre-eclampsia. ICS use should not be stopped in pregnancy - inadequately controlled asthma is more dangerous than the medication.

Key Teaching Points

1. Asthma = inflammation first, bronchospasm second. Treating only bronchospasm (SABA alone) without addressing inflammation leads to poor long-term control.
2. The triad for diagnosis: reversible airway obstruction + airway inflammation + airway hyperresponsiveness.
3. "Not all that wheezes is asthma, and not all asthma wheezes" - always consider differentials.
4. ICS is the cornerstone of maintenance therapy for all persistent asthma.
5. LABA must never be used as monotherapy - only in combination with ICS.
6. Control comorbid rhinitis - the "one airway" concept matters clinically.
7. Self-management education (written action plan + PEFR monitoring) prevents most exacerbations.
8. A normalizing PCO2 in a still-struggling asthma patient is an emergency warning sign.