Lung Diseases and Airflow Mechanics

Airflow in Healthy Lungs

• Inhaled air travels through the pharynx, trachea, bronchi, bronchioles, and ultimately reaches the alveoli.
• Alveoli are the primary sites for gas exchange.

Obstructive Lung Disease

• Characterized by reduced gas exchange due to impaired airflow in and out of the alveoli.
• Conditions causing obstruction include:
  • Asthma
  • Bronchiectasis
  • Chronic Bronchitis
  • Emphysema
  • Foreign Body Obstruction

Restrictive Lung Disease

• Results in limited airflow as the lungs cannot expand fully.
• Common causes include:
  • Pulmonary stiffness or muscle rigidity
  • Pneumonia
  • Pleurisy
  • Pleural Effusion
  • Pneumothorax
  • Respiratory depression from CNS issues
  • Acute Respiratory Distress Syndrome (ARDS)
  • Sudden Infant Death Syndrome (SIDS)

Asthma

• Involves chronic airway inflammation leading to hyperresponsiveness, mucosal edema, and increased mucus production.
• Initially reversible, can progress to irreversible with worsening pathology.
• Predisposing factors include atopy and female gender.
• Causal factors involve exposure to allergens and occupational sensitizers.

Contributing Factors of Asthma

• Respiratory infections
• Air pollution
• Active and passive smoking
• Other factors: diet, small birth size

Risk Factors for Asthma Exacerbations

• Allergens
• Respiratory infections
• Exercise and hyperventilation
• Weather changes
• Sulfur dioxide exposure
• Food or medication sensitivities

Symptoms of Asthma

• Wheezing
• Coughing, with or without mucus
• Dyspnea (difficulty breathing)
• Chest tightness

Inflammatory Response in Asthma

• Mast cells release mediators like histamine and leukotrienes, perpetuating inflammation.
• Results in increased blood flow, vasoconstriction, fluid leakage, increased mucous secretion, and bronchoconstriction.

Clinical Manifestations of Asthma

• Symptoms may worsen progressively or occur abruptly.
• Notable symptoms include:
  • Cough
  • Dyspnea from constricted airways
  • Wheezing during expiration, potentially progressing to inspiration
  • Tachycardia
  • Diaphoresis
  • Cyanosis indicates hypoxemia (late sign).
  • Status Asthmaticus represents a life-threatening condition.

Diagnostics for Asthma

• Medical history and physical examination focusing on familial and environmental factors.
• Laboratory tests may reveal:
  • Eosinophilia during acute episodes
  • Elevated serum IgE with allergic triggers
  • Arterial blood gas analysis indicating hypocapnia from rapid breathing, leading to respiratory alkalosis.
  • Pulse oximetry may show decreased oxygen saturation.

Medical Management of Asthma

• Administering oxygen for hypoxia.
• Monitoring blood gases during severe attacks to prevent acidosis.
• Pulse oximetry for acutely ill patients.
• Treating underlying allergic reactions.
• Using smooth muscle relaxants and steroids (inhaled/systemic).
• Spirometry for assessing treatment efficacy.

Pharmacologic Management of Asthma

• Short-acting beta2-adrenergic agonists (SABA): e.g., albuterol; they relax smooth muscles.
  • Dosage:
    • Nebulized: 2.5 – 5 mg every 20 minutes for 3 doses.
    • MDI: 4 – 6 puffs every 20 minutes for 3 doses.
• Anticholinergics: Inhibit muscarinic receptors to reduce vagal tone in the airways; e.g., Ipratropium.