Summary
Highlights
Asthma is a chronic inflammatory disorder affecting the bronchi and bronchioles, leading to bronchoconstriction and excessive mucus production during attacks. Unlike COPD, asthma attacks are reversible and typically don't cause long-term alveolar damage. Triggers include irritants like smoke, pollen, dust, strenuous activity, and cold weather. An asthma attack involves inflammation, tightening of the bronchi, and increased mucus, leading to air trapping and difficulty exhaling, potentially causing acidosis.
Key signs and symptoms of an asthma attack are remembered by the acronym ASTHMA: Accessory muscle use (paradoxical breathing being a critical sign), Shortness of breath (dyspnea, especially single-word dyspnea), Tight chest and tachypnea, High-pitched wheezing, Minimal/diminished breath sounds, and Absent breath sounds (silent chest, a priority sign signaling severe obstruction). Early stages of an acute attack may present with respiratory alkalosis due to hyperventilation, progressing to respiratory acidosis in later, exhausted stages due to CO2 retention.
High carbon dioxide levels can lead to hypercapnic respiratory failure, an 'acid crisis' indicated by a pH < 7.35, PaCO2 > 45, and PaO2 < 80. The first signs of hypoxia (low oxygen) are mental status changes: agitation, restlessness, then drowsiness. Status asthmaticus is a medical emergency where an asthma attack doesn't respond to medication, leading to severe inflammation and potential death. A key sign of this is pulsus paradoxus, a drop in systolic blood pressure of more than 10 mmHg during inhalation, due to increased negative pressure in the lungs affecting the heart.
The Peak Expiratory Flow Rate (PEFR), measured by a peak flow meter, helps monitor asthma control. It uses a traffic light system: Green zone (80-100% control, no medication needed), Yellow zone (50-80% control, indicating a need for rescue drugs and a call to the healthcare provider), and Red zone (<50% control, requiring immediate emergency treatment). Proper use of the peak flow meter involves three attempts, with the highest score recorded. A personal best score is established over a 2-week period when asthma is controlled, not from daily readings.
Asthma triggers are categorized into extrinsic (external) and intrinsic (internal) factors. Extrinsic triggers include allergens like dander, dust, pollen, indicated by elevated eosinophils and a type 1 hypersensitivity reaction involving IgE antibodies and mast cell activation. Intrinsic triggers (non-allergic asthma) are from inside the body, such as sickness (respiratory infections), stress, severe weather (cold), and strenuous activity. Patients should use medication 20-30 minutes before exercise to prevent exercise-induced attacks, not avoid activity. NSAIDs and non-selective beta-blockers (like propranolol) can also trigger asthma attacks.
Asthma medications are divided into bronchodilators (BAM team) and anti-inflammatory agents (SLAM team). Bronchodilators include Beta-2 agonists (Albuterol, the primary rescue drug), Anticholinergics (Ipratropium, which dries secretions and dilates airways), and Methylxanthines (Theophylline, which is toxic with a therapeutic range of 10-20 mcg/mL). Anti-inflammatory agents include Steroids (ending in -sone, like beclomethasone), which can cause oral thrush (requiring mouth rinsing), increase infection risk, and elevate blood sugar. Other less commonly tested medications include Leukotriene inhibitors (e.g., Montelukast) and Mast cell stabilizers (e.g., Cromolyn). Proper meter-dosed inhaler technique involves shaking the canister before use and holding breath for 10 seconds after inhalation.