Obstructive Pulmonary Diseases
Objectives - Identify obstructive disease facts and principles for COPD, cystic fibrosis, chronic bronchitis, asthma, bronchiectasis, and emphysema.
Obstructive Disease Overview
The source uses CBABE as the obstructive disease memory aid:
- Cystic fibrosis
- Bronchitis
- Asthma
- Bronchiectasis
- Emphysema
The American Thoracic Society definition in the source describes COPD as a preventable and treatable disease characterized by airflow limitation that is not fully reversible. The airflow limitation is usually progressive and associated with a chronic inflammatory response of the lungs to noxious particles or gases.
COPD is a nonspecific term referring to conditions that develop progressively from several disease processes, most commonly chronic bronchitis, emphysema, and asthma.
Obstructive Disease Diagnosis
| Test or Measure | Obstructive Pattern |
|---|---|
| Spirometry | Primary test for obstructive lung disease; measures flows and volumes |
| Lung volumes | Measures RV/FRC and TLC |
| Diffusion | Measures how well oxygen moves across the alveolar-capillary membrane |
| Airway resistance | High |
| Compliance | Normal or high |
| ABG acid-base status | PaCO2, pH, and HCO3 assess ventilation and acid-base status |
High-yield gas exchange distinctions:
- PaO2 = oxygenation
- SaO2 = oxygenation
- PaCO2 = ventilation
Cystic Fibrosis
Cystic fibrosis is a genetic disorder caused by mutations in the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein.
CFTR controls chloride ion movement through cell membranes and is involved in production of sweat, digestive fluids, and mucus. When CFTR is not functional, secretions become thick and cause persistent lung infections.
Cystic Fibrosis Manifestations
| System | Source Findings |
|---|---|
| Pulmonary | Copious thick mucoid secretions clog airways and trap bacteria, leading to recurring infections, atelectasis, bronchiectasis, hyperinflation, and severe hypoxemia |
| Pulmonary infections | Staphylococcus aureus, Haemophilus influenzae, and Pseudomonas aeruginosa |
| Pancreas | Mucus prevents release of digestive enzymes needed to break down food and absorb nutrients |
| Nutrition | Malnutrition and deficiencies of fat-soluble vitamins A, D, E, and K |
| Sweat glands | Unable to remove salt from sweat; skin is very salty and patients dehydrate easily |
Cystic Fibrosis Diagnosis
Clinical clues include recurrent pulmonary infections, failure to grow, and family history.
Both parents must be carriers:
| Child Outcome | Source Probability |
|---|---|
| Has CF | 25% |
| Carrier without CF | 50% |
| Not a carrier and does not have CF | 25% |
Diagnosis is confirmed by the sweat chloride test.
| Sweat Chloride Result | Interpretation |
|---|---|
| Less than 40 mEq/L | Normal |
| 40-60 mEq/L | Borderline; repeat test |
| Greater than 60 mEq/L | Positive |
Monitoring includes spirometry, chest x-ray, and sputum cultures.
Cystic Fibrosis Treatment
Treatment options listed in the source include:
- Airway clearance therapy
- Exercise
- Inhaled bronchodilators
- Recombinant deoxyribonuclease (DNase), Pulmozyme
- 7% hypertonic saline
- Antibiotics, including tobramycin
- Lung transplantation
The source also lists Trikafta as newer additional information that addresses the root cause of cystic fibrosis: mutations in the CFTR gene. It was released in 2019.
Chronic Bronchitis
Chronic bronchitis is inflammation of the bronchial airways that causes a productive cough.
| Type | Definition |
|---|---|
| Acute bronchitis | Usually caused by viruses, typically cold and flu viruses |
| Chronic bronchitis | Chronic productive cough for at least 3 months per year for two consecutive years, after other causes of chronic cough are ruled out |
Other causes to rule out include GERD, asthma, and postnasal drip.
Chronic Bronchitis Causes and Changes
Causes listed in the source:
- Cigarette smoke
- Air pollution or dust
- Exposure to toxic gas, fumes, or chemicals
Pathologic changes include:
- Hypersecretion of mucus
- Ciliary dysfunction
- Airway mucosal inflammation and edema
- Excessive secretions causing mucus plugging
- Hyperinflation of alveoli
- Bronchoconstriction
Chronic Bronchitis Signs, Symptoms, Diagnosis, and Treatment
| Category | Findings |
|---|---|
| Signs | Productive cough with clear, white, yellowish, green, or rarely blood-streaked sputum; low-grade fever; "blue bloater" pattern; generally overweight; blue cyanotic skin color |
| Symptoms | Shortness of breath, chest discomfort, fatigue |
| PFT | Spirometry decreased, lung volumes normal, DLCO normal |
| ABG | PaO2 normal or decreased; PaCO2 normal or increased |
| Other diagnostics | History and physical, x-ray |
| Treatment | Monitor PFT, ABG, and x-ray; smoking cessation; bronchodilator therapy; oxygen therapy; pulmonary rehab |
Asthma
Asthma is a syndrome characterized by airway obstruction due to airway inflammation and/or airway hyper-responsiveness (bronchospasm) due to various stimuli. The obstruction is partially or completely reversible either spontaneously or with treatment.
Source incidence points:
- 1 in 13 people, or 25 million
- Increasing in prevalence
- In 2016: 3,500 deaths, 450,000 hospitalizations, and 1.8 million ER visits
Asthma Pathogenesis
Triggers include:
- Allergens
- Respiratory infections
- Occupational or environmental exposures
- Exercise or hyperventilation
- Cold dry air
- Cigarette smoke
- Inhaled irritants
- Stress
Inhaled allergen causes IgE molecules to attach to mast cells in the bronchial mucosa. Mast cells degranulate and release histamine, leukotrienes, prostaglandins, and platelet-activating factor.
IgE antibodies are produced by the immune system and travel to cells that release chemicals, causing an allergic reaction.
Asthma Symptoms, Diagnosis, and Management
| Category | Findings |
|---|---|
| Symptoms | Episodic wheezing or bronchospasm, shortness of breath, chest tightness, cough |
| Diagnosis | History, physical, wheezing on auscultation, rhinitis, cough, PFT with FEV1 and FEV1/FVC, bronchial provocation testing such as MCT or EIA, allergy testing |
| Management component 1 | Measurement and monitoring of lung function: PFT using FEV1 and FEV1/FVC, routine peak flow |
| Management component 2 | Pharmacologic therapy: bronchodilator, inhaled corticosteroid, mediator modifiers |
| Management component 3 | Environmental control: eliminate triggers including outdoor allergens, household dust, warm-blooded pets, carpet, and bedding not washed weekly in hot water |
| Management component 4 | Patient education |
Bronchiectasis
Bronchiectasis is abnormal, permanent dilation and thickening of the airways caused by an inflammatory response from recurring infections in the lungs.
Bronchiectasis Causes
Causes listed in the source include:
- Most often secondary to pulmonary infections
- Foreign body aspiration
- Primary ciliary dyskinesia, including Kartagener syndrome
- Cystic fibrosis
Bronchiectasis Signs, Diagnosis, and Treatment
| Category | Findings |
|---|---|
| Signs and symptoms | Classic cough and mucopurulent sputum production lasting months to years; blood-streaked sputum or hemoptysis; dyspnea; pleuritic chest pain; wheezing; fever; weakness; fatigue; weight loss |
| Diagnosis | Patient history of chronic daily cough and purulent sputum, obstructive PFT results, sputum cultures, chest x-ray, high-resolution CT as the standard diagnostic test |
| Treatment | Antibiotics and airway clearance, bronchodilators, corticosteroids, dietary supplementation, oxygen for hypoxemic patients, hospitalization for severe exacerbations, surgical therapies for localized disease only |
Emphysema
Emphysema is abnormal, permanent enlargement of airspaces beyond the terminal bronchioles, accompanied by destruction of alveolar walls.
Emphysema Causes and Structural Changes
Causes match chronic bronchitis in the source:
- Cigarette smoke
- Air pollution or dust
- Exposure to toxic gas, fumes, or chemicals
The protease-antiprotease theory states that acinar walls are destroyed when there is an imbalance between proteases and antiproteases in the lung. Proteases such as elastase digest connective tissue elements and are found especially in neutrophils and macrophages. Smoking increases lung proteases while impairing antiproteases.
Alpha1-antitrypsin deficiency accounts for 5% in the source. Alpha1-antitrypsin is a glycoprotein produced by the liver. When old white blood cells are destroyed in the lungs, elastase is released and can destroy elastic tissue. Alpha1-antitrypsin should deactivate elastase; deficiency prevents that protection.
Pathologic and structural changes include:
- Permanent enlargement and destruction of airspaces
- Destruction of pulmonary capillaries
- Weakened distal airways
- Bronchospasm
- Air trapping
Emphysema Signs, Diagnosis, and Treatment
| Category | Findings |
|---|---|
| Signs | Slight cough with small mucoid secretions, labored breathing with prolonged expiratory time, increased AP chest measurement, barrel chest, orthopnea, "pink puffer," pursed-lip breathing, pink skin color and not cyanotic |
| Symptoms | Fatigue and dyspnea |
| ABG early stage | Relatively normal except during exacerbations; PaO2 normal or decreased; PaCO2 normal or increased |
| ABG late stage | Fully compensated respiratory acidosis with mild to moderate hypoxemia |
| PFT | FEV1/FVC decreased, FEV1 decreased, lung volumes increased, DLCO decreased |
| X-ray | Flattened diaphragms, translucent lung fields, enlarged heart and/or long narrow heart, hyperinflation |
| Treatment | Monitor PFT, ABG, and x-ray; smoking cessation; bronchodilator therapy; oxygen therapy; pulmonary rehab; lung reduction surgery |
High-Yield Review
| Disorder | High-yield point |
|---|---|
| COPD | Airflow limitation that is not fully reversible and is usually progressive |
| Cystic fibrosis | CFTR problem causes thick secretions and persistent lung infections |
| Chronic bronchitis | Productive cough at least 3 months per year for two consecutive years |
| Asthma | Reversible airway obstruction from inflammation and/or hyper-responsiveness |
| Bronchiectasis | Permanent airway dilation from inflammatory response to recurring infections |
| Emphysema | Permanent enlargement beyond terminal bronchioles with alveolar wall destruction |
| Obstruction testing | Spirometry is primary; airway resistance is high; compliance is normal or high |