N225 - Week 3 Study Guide: Asthma and Chronic Obstructive Pulmonary Disease (COPD)

Pathophysiology and Immune Mechanisms of Asthma

• Definition: Asthma is defined as a chronic inflammatory disorder of the airways. This inflammation is largely reversible with pharmacological intervention and environmental control.
• General Airway Changes:
  • Inflammation: The primary process involves swelling of the airway tissues.
  • Mucus Production: Excessive sticky fluids build up, responding to immunoglobulins and inflammatory cells.
  • Diameter Reduction: Swelling and mucus combine to decrease the diameter of the airway, restricting oxygen flow ($O_2$) and increasing the difficulty of breathing.
  • Bronchoconstriction: Contraction of the smooth muscles around the airways narrows them further.
• The Filtering System (Normal vs. Asthmatic):
  • Normal: The nose acts as a "fly trapper," using thick mucus to catch dirt, pollen, and smoke. Cilia (small hairs) move this mucus to the throat to be swallowed or spit out. "Postnusial drip" during pollen season is evidence of the nose working overtime to protect the lungs.
  • Asthmatic Overdrive: The immune system goes into a state of hyper-inflammation. It mistakenly tags harmless substances (allergens) as dangerous.
• Cellular and Molecular Response:
  • Immunoglobulin E ($IgE$): Plays the main role in reacting to triggers (smoke, dust, bacteria). Triggers cause the release of $IgE$ antibodies.
  • Mast Cells: The first line of defense. When activated by $IgE$, they release granules containing mediators like histamine, prostaglandins, and leukotrienes.
  • Additional Immune Cells: Eosinophils, macrophages, and lymphocytes are recruited to the site of inflammation.
• Timed Responses:
  • Early Asthmatic Response: Immediate restriction of airways and increased mucus production following exposure.
  • Late Asthmatic Response: Occurs $3-6$ hours later. Pro-inflammatory cytokines recruit additional immune cells (like eosinophils), leading to sustained bronchoconstriction.

Clinical Manifestations and Symptom Progression

• Classic Symptoms:
  • Wheezing.
  • Breathlessness/Shortness of breath.
  • Chest tightness.
  • Coughing (may be productive or non-productive due to irritation).
• Wheezing Characteristics:
  • Mild Attack: Typically presents as an expiratory wheeze (heard when breathing out).
  • Severe Attack: As narrowing increases, wheezing is heard on both inspiration and expiration. It may progress to "stridor," indicating extreme narrowing.
• The "Silent Chest":
  • This is an ominous and bad sign. It occurs when breath sounds become diminished, decreased, or absent.
  • It indicates that no air is moving through the airways. It is a medical emergency requiring immediate notification of a provider.
• Ventilation vs. Diffusion:
  • Ventilation: The process of getting air down to the alveoli.
  • Diffusion: The actual exchange of oxygen into the bloodstream.
  • Asthma is primarily a ventilation issue due to restricted airways preventing air from reaching the alveoli.
• Respiratory Failure Progression (ABGs):
  • Early Sign: Hyperventilation. The patient breathes fast (Respiratory Rate $> 20$). This causes them to blow off too much carbon dioxide ($CO_2$), leading to Respiratory Alkalosis.
  • Late Sign: Exhaustion. The patient cannot maintain a high respiratory rate forever. The rate eventually drops ($< 12$). This leads to Respiratory Acidosis as they retain $CO_2$ (hypercapnia).

Diagnostic Tools and Monitoring

• Spirometry:
  • A diagnostic device that measures the volume of air inhaled and exhaled.
  • Procedure: Patients blow into the device as hard and fast as possible. This is done before and after administering a beta-agonist (bronchodilator).
  • Criteria for Diagnosis: Improvement in the Forced Expiratory Volume ($FEV1$) of at least $12\%$ or $200\,ml$ after the bronchodilator indicates reversible obstruction (Asthma), unlike COPD.
  • Patient Education: Patients should hold their bronchodilators for $6-12$ hours prior to a follow-up spirometry test.
• Peak Flow Meter:
  • Used for daily monitoring. Patients establish a "personal best" by recording the highest number achieved over a week while well-controlled.
  • The Lower the Number: The more airflow obstruction is present.
• Management Zones:
  • Green Zone ($80-100\%$ of personal best): Well-controlled; stay on current meds.
  • Yellow Zone ($50-80\%$ of personal best): Caution; having symptoms. Take rescue inhaler (SABA) and monitor.
  • Red Zone ($< 50\%$ of personal best): Danger zone. Take rescue medication immediately and seek medical help.
• Other Diagnostics:
  • Chest X-ray: Usually normal in asthma; used to rule out secondary causes like infection.
  • CT Scan: Done if the patient is not responding to treatment (to check for tumors or obstructions).
  • BMP (Basic Metabolic Panel): Monitor potassium ($K^+$) because Albuterol can cause hypokalemia.

Asthma Pharmacology and Nursing Management

• Short-Acting Beta Agonists (SABA):
  • Example: Albuterol.
  • Use: Rescue medication for acute attacks or pre-exposure (e.g., $10-15$ minutes before exercise or visiting someone with a cat).
  • Side Effects: Tachycardic palpitations, tremors/shakiness, and low potassium.
• Long-Acting Beta Agonists (LABA):
  • Examples: Salmeterol, Formoterol (end in "-erol").
  • Use: Daily preventative/controller medication; not for acute attacks.
• Anticholinergics:
  • Examples: Ipratropium (short-acting), Tiotropium (long-acting).
  • Mechanism: Prevents muscles from contracting/narrowing.
• Corticosteroids:
  • Anti-inflammatory: Helps keep inflammation under control.
  • Routes: Inhaled (daily), Oral (Prednisone for transitions), or IV (Methylprednisolone for acute exacerbations).
  • Education (Inhaled): Patients must rinse their mouth after use to prevent oral candidiasis (thrush).
• Inhaler Techniques:
  • Metered-Dose Inhaler (MDI): Shake first. Breathe in slowly. Use a spacer to ensure medication reaches deep airways instead of just the back of the throat.
  • Dry Powder Inhaler (DPI): Breath-activated. Requires a fast, deep breath in. Do not shake.
• Acute Management (Status Asthmaticus):
  • Severe, non-responsive attack.
  • Treatment Trio: Albuterol/Ipratropium nebulizers, IV Methylprednisolone, and IV Magnesium (to relax smooth muscles).
  • Last Resorts: Epinephrine, IV fluids, and mechanical ventilation/intubation (avoided if possible to prevent further airway irritation).

Chronic Obstructive Pulmonary Disease (COPD)

• Definition: Chronic inflammation and narrowing of airways with damaged air sacs (alveoli). It is progressive and irreversible.
• Risk Factors: Cigarette smoking (primary), secondhand smoke, air pollution, occupational dust, and genetic alpha-1 antitrypsin deficiency.
• Pathophysiology Processes: Loss of alveolar attachments, inflammatory obstruction, and mucus production.
• Chronic Bronchitis ("Blue Bloaters"):
  • Productive cough for at least $3$ months in a year for $2$ consecutive years.
  • Characteristics: Overweight, cyanotic (blue hue), dyspneic, edema (fluid retention), and potential right-sided heart failure (cor pulmonale).
• Emphysema ("Pink Puffers"):
  • Damage to the alveoli leading to gas trapping.
  • Characteristics: Cachectic (thin/frail), barrel chest, red/pink hue (body over-produces red blood cells to compensate for low $O_2$), and use of accessory muscles for breathing.
• Clinical Signs of COPD:
  • Barrel Chest: The anterior-posterior (AP) diameter to transverse diameter is $1:1$ (normally $2:1$).
  • Diminished Breath Sounds: Expected in the barrel-chested COPD patient due to extra air space.
  • Hyperinflated Lungs: Visible on X-ray; the diaphragm appears flat instead of curved.
• COPD Management:
  • Oxygen Target: Should be maintained between $88-92\%$. High oxygen can suppress their drive to breathe (hypoxic drive).
  • Nutrition: Eat small, frequent, high-calorie meals. Avoid carbonated/gassy foods (beans, cabbage, soda) that press against the diaphragm.
  • Breathing Techniques: Pursed-lip breathing (like blowing out birthday candles or sucking a milkshake) to prevent air trapping.
  • Diaphragmatic Breathing: Strengthens the diaphragm to reduce use of accessory muscles.

Arterial Blood Gas (ABG) Review

• Normal Values:
  • $pH$: $7.35-7.45$.
  • $CO_2$: $35-45\,mmHg$.
  • $HCO_3$: $22-26\,mEq/L$.
• Logic (ROAM): Respiratory Opposite, Metabolic Equal.
  • Respiratory Alkalosis: High $pH$ and Low $CO_2$ (Early asthma/Hyperventilation).
  • Respiratory Acidosis: Low $pH$ and High $CO_2$ (Late asthma or COPD/Hypoventilation).

Questions & Discussion

• Question: What is a risk factor for asthma described in a history?
• Response: Allergic rhinitis (allergies), history of chronic sinusitis, cough (especially at night), and shortness of breath from exercise.
• Question: If a patient is wheezing and then goes silent, is that self-correction?
• Response: No. It is "Silent Chest," meaning no air is moving, and the provider must be alerted immediately.
• Question: Why do we sit the patient up?
• Response: Sitting up (High Fowler's) helps decrease pressure on the chest, making it easier to breathe.