Asthma | Medical Science Optional Notes for UPSC PDF Download

Etiology

Allergic Asthma (Extrinsic Asthma)

• Primary risk factor: Atopy (genetic predisposition to allergic reactions).
• Environmental allergens include:
  • Seasonal pollen
  • Dust mites
  • Domestic animals
  • Mold spores
• Allergic Occupational Asthma: Occurs due to exposure to allergens in the workplace, such as flour dust.
• About 10% of asthmatic patients exhibit non-allergic or intrinsic asthma:
  • Negative skin tests for common inhalant allergens
  • Normal serum IgE concentrations
  • Typically, later onset of disease (adult-onset asthma)
  • Commonly associated with nasal polyps
  • Potential sensitivity to aspirin.

Nonallergic Asthma (Intrinsic Asthma)

Triggers include:

• Cold air
• Physical exertion (exercise-induced asthma)
• Gastroesophageal reflux disease (GERD), often coexists with asthma
• Chronic sinusitis or rhinitis
• Medications such as aspirin/NSAIDs (aspirin-induced asthma) and beta blockers
• Viral respiratory tract infections
• Stress
• Irritant-induced asthma (from exposure to solvents, ozone, tobacco or wood smoke, cleaning agents).

Pathogenesis

Asthma is generally characterized by the following three processes:

• Bronchial Hyperresponsiveness:
  • Definition: Increased sensitivity of the bronchial tubes to various stimuli.
  • Consequence: Heightened reactivity that can lead to bronchoconstriction.
• Bronchial Inflammation:
  • Description: Inflammation occurs in the terminal bronchioles.
  • Characteristics: These bronchioles are lined with smooth muscle but lack the cartilage found in larger airways.
  • Result: Inflammation is a primary cause of asthma symptoms.
• Symptoms Caused by Inflammation of Terminal Bronchioles:
  • Trigger: Allergens can initiate a hypersensitivity reaction.
  • Reaction: Bronchial submucosal edema and smooth muscle contraction occur.
  • Consequence: Collapse of bronchioles due to the absence of cartilage support.
  • Manifestation: Asthma symptoms result from this process.

Endobronchial Obstruction Caused by:

• Bronchospasm: Constriction of the bronchioles.
• Mucosal Edema: Swelling of the bronchial lining.
• Hypertrophy of Smooth Muscle Cells: Enlargement of smooth muscle in the bronchioles.
• Increased Mucus Production: Excessive production of mucus contributing to obstruction.

Bronchial Asthma-Pathogenesis

Bronchial Asthma-Management

Prodromal Symptoms

Itching under the chin, discomfort between shoulder blades, and a sense of impending doom.

Symptoms

• Wheezing, difficulty breathing, and coughing, with thick, hard-to-cough-up mucus.
• Symptoms often worse at night, commonly awakening patients in the early morning hours.
• Chest tightness, and in severe cases, pulsus paradoxus—an exaggerated drop in blood pressure during inhalation.

Signs

• Expiratory rhonchi across the chest, indicating hyperinflation.
• Reduced breath sounds, potentially leading to a silent chest.

Diagnosis

Pulmonary function tests:

• Obstructive pattern characterized by reduced FEV1, FEV1/FVC ratio, reversible with a >12% and 200 mL increase in FEV1 after using a short-acting beta2 agonist.
• Decreased PEF (Peak Expiratory Flow).
• Flow volume loops showing reduced peak flow and maximum expiratory flow.

Provocative Tests

• Methacholine or histamine challenge tests: Trigger a 20% reduction in FEV1.
• Exercise test revealing post-exercise bronchoconstriction.
• Allergen challenge test and serum IgE level assay.
• Chest X-ray often shows hyperinflation.
• Skin tests for common allergens.

Differential Diagnosis

• Chronic Obstructive Pulmonary Disease (COPD):
  • Chronic inflammatory lung disease.
  • Shares symptoms with asthma but has distinct characteristics.
• Upper Airway Obstruction by a Tumor or Laryngeal Edema:
  • Manifests as stridor localized to large airways.
  • Flow-volume loops display reduced inspiratory and expiratory flow.
  • Bronchoscopy reveals narrowing in the upper airway.
• Endobronchial Obstruction with a Foreign Body:
  • Presence of a foreign object causing persistent symptoms in a specific area of the chest.
• Left Ventricular Failure (Cardiac Asthma):
  • Noted by basilar crackles.
  • Heart failure-related pulmonary symptoms that may mimic asthma.

Acute asthma-Management

Acute Asthma-acute, reversible episode of lower airway obstruction that may be life-threatening.

Management of Chronic Asthma

Avoidance of Triggers

• Allergens
• Upper respiratory tract viral infections
• Exercise and hyperventilation
• Cold air
• Sulfur dioxide and irritant gases
• Drugs (beta-blockers, aspirin)
• Stress
• Irritants (household sprays, paint fumes)

Step wise therapy

(i) Evaluating the Severity of Asthma:

• Determining the extent of asthma severity.
• Assessing the level of symptom manifestation and frequency.

(ii) Choosing Medications:

• Selecting appropriate medications based on the identified severity.
• Considering low doses of theophylline or an antileukotriene as supplementary therapies.
• Acknowledging that these options are not as effective as long-acting beta-agonists (LABA).

(iii) Choosing Suitable Inhalation Devices:

• Opting for inhalation devices that align with the patient's needs and preferences.
• Ensuring the selected device facilitates effective medication delivery.

(iv) Monitoring:

• Regularly tracking and assessing the patient's response to the prescribed treatment.
• Adjusting medication or treatment plans as needed for optimal asthma management.

Additionally, for steroid-dependent asthmatics not adequately controlled, the consideration of alternative therapies such as omalizumab and anti-IL-5 may be explored in specific cases.

Acute Onset of Breathlessness

Differential Diagnosis

• Pulmonary edema
• Massive pulmonary embolus
• Acute severe asthma
• Acute exacerbation of COPD
• Pneumonia
• Metabolic acidosis
• Psychogenic causes
• Inhalation of a foreign body
• Acute epiglottitis

Investigations

• Arterial Blood Gas Analysis
• Chest X-ray
• Peak Expiratory Flow Rate

Immediate Assessment for Acute Severe Asthma

Criteria:

• PEF between 33-50% predicted
• Respiratory rate > 25/min
• Heart rate > 110/min
• Inability to complete sentences in one breath

Management Protocol for Acute Severe Asthma

Initial Steps:

• Reassure the patient to alleviate anxiety worsening respiratory distress.
• Position the patient upright.
• Begin oxygen inhalation to maintain saturation above 92%.

Management for Different Exacerbation Levels

• Mild Exacerbation (PEF 76%-100%): Administer Salbutamol Inhalation and observe for improvement.
• Moderate Exacerbation (PEF 51%-75%): Provide Salbutamol or Terbutaline nebulization along with oral corticosteroids.
• Severe Exacerbation (PEF 0%-50%): Introduce inhaled bronchodilation with Ipratropium bromide.
  • Establish IV access for corticosteroids and monitor potassium levels due to potential hypokalemia from salbutamol.
  • Consider IV MgSO4 or IV Aminophylline for refractory cases.

Life-Threatening Features Indicating Mechanical Ventilation

• PEF <33% predicted or Spo2<92% or Pao2<8kpa
• Abnormal respiratory signs like silent chest, cyanosis, feeble respiratory effort, bradycardia, arrhythmia, hypotension, exhaustion, confusion, or coma.

Bronchial Asthma-Repeats

Q1: Describe the treatment of an acute case of Bronchial Asthma. (1994) 

Q2: Discuss severe Acute Asthma. (1997)

Q3: How will you manage a case of acute severe bronchial asthma? (2010) 

Q4: A 17-year-old girl, with a history of seasonal wheezing, off and on, presents to the casualty with sudden onset breathlessness. (2016)
(i) Describe the aetiopathogenesis of this condition.
(ii) Discuss the short-term and long-term management of this disorder.