CH.31 Obstructive Pulmonary Disease Pg. 656-657 (COPD - Chronic Bronchitis) Pg. 648-650 Drug Therapy Table

Chronic Obstructive Pulmonary Disease (COPD)

• Definition: COPD is a progressive lung disease characterized by persistent airflow limitation.

• Pathophysiology: It is associated with an enhanced chronic inflammatory response in the airways and lungs.

• Main Causes:

  • Cigarette smoking

  • Exposure to other noxious particles and gases

• Contributing Factors: Exacerbations and coexisting problems can increase the severity of the disease.

• Related Conditions:

  • Chronic Bronchitis: Defined as the presence of cough and sputum production for at least 3 months in each of 2 consecutive years. It can precede or follow the development of airflow limitation.

  • Emphysema: Involves the destruction of alveoli without fibrosis and describes one of several structural abnormalities in COPD.

• Statistics:

  • Approximately 16 million adults in the US have COPD, but many cases remain undiagnosed until moderate to advanced stages.

  • COPD is the third leading cause of death in the US, resulting in over 140,000 deaths annually.

Risk Factors for COPD

• Effects of Tobacco Smoke on the Respiratory System

  Area of Defect	Acute Effects	Long-Term Effects
  Respiratory mucosa
  - Nasopharyngeal	↓ Sense of smell	Cancer
  - Tongue	↓ Sense of taste	Cancer
  - Vocal cords	Hoarseness	Chronic cough, cancer
  - Bronchus and bronchioles	Bronchospasm, cough	Chronic bronchitis, asthma, cancer
  - Cilia	Paralysis, sputum accumulation,no cough	Chronic bronchitis, cancer
  - Mucous glands	↑ Secretions, ↑ cough	Hyperplasia and hypertrophy of glands, chronic bronchitis
  - Alveolar macrophages	↓ Function	↑ Incidence of infection
  Elastin and collagen fibers
  - ↑ Destruction by proteases
  - ↓ Function of antiproteases (α1-antitrypsin)
  - ↓ Synthesis and repair of elastin		Emphysema

Biological Sex Considerations in COPD

• Men:

  • COPD is slightly more common in men.

  • Men have a poorer response to O2 therapy.

• Women:

  • The prevalence of COPD is increasing among women, likely due to more women smoking and increased susceptibility (e.g., smaller lungs and airways).

  • Women who smoke are 50% more likely to develop COPD compared to men who smoke.

  • Women with COPD tend to have a lower quality of life, more exacerbations, less phlegm, and increased dyspnea.

Cigarette Smoking as a Major Risk Factor for COPD

• Prevalence: Cigarette smoking is the major risk factor for developing COPD. Approximately 38% of the 16 million people in the US with COPD report that they currently smoke. Individuals over the age of 40 with a smoking history of 10 or more pack-years should be evaluated for COPD.

• Direct Effects of Cigarette Smoke on the Respiratory Tract:

  • Smoke irritates the respiratory tract, leading to hyperplasia of cells, including goblet cells, which increases mucus production.

  • This hyperplasia reduces airway diameter and complicates mucus clearance.

  • Smoking reduces ciliary activity and can lead to the actual loss of cilia.

  • Abnormal dilation of distal air spaces and destruction of alveolar walls occurs.

  • Pre-cancerous changes can be seen, with many cells showing large, atypical nuclei.

  • Chronic smoking leads to enhanced inflammation and structural remodeling of lung tissue over time.

• Oxidative Stress and Protease-Antiprotease Imbalance:

  • Smoking induces oxidative stress, leading to an imbalance between proteases that degrade lung connective tissue and antiproteases that protect it.

  • These changes worsen with disease severity and can persist even after cessation of smoking.

• Environmental Tobacco Smoke (ETS):

  • In adults, ETS can cause decreased lung function, increased respiratory symptoms, and severe lower respiratory tract infections, including pneumonia.

  • ETS is associated with an increased risk of nasal sinus and lung cancer.

• Other Risk Factors:

  • Infection: Severe recurrent respiratory tract infections in childhood may lead to reduced lung function and increased symptoms in adulthood. Smoking combined with HIV infection can accelerate COPD development, and tuberculosis is also a risk factor.

  • Asthma: Patients with COPD may also have asthma, known as asthma-COPD overlap syndrome.

  • Air Pollution: While the impact of outdoor air pollution on COPD development is uncertain, exposure to coal and biomass fuels in poorly ventilated areas represents another risk.

  • Occupational Chemicals and Dusts: Exposure to various workplace irritants can lead to COPD symptoms, and the risk is significantly higher for smokers.

  • Aging: Aging may be a risk factor for COPD, but research is inconclusive. Changes associated with aging—such as stiffening of the chest wall, loss of elastic recoil, and decreased gas exchange efficiency—are similar to those seen in patients with COPD.

Overall, the risk for developing COPD is influenced by a combination of smoking, environmental factors, infections, asthma, and occupational exposures, alongside the aging process.

α1-Antitrypsin Deficiency (AATD)

Genetic Basis

• Autosomal Recessive Disorder: AATD is an autosomal recessive disorder.

• Gene Function: The SERPINA1 gene provides instructions for the liver to make the protein α1-Antitrypsin (AAT), which protects the lungs and liver from proteolytic enzymes.

• Mutations: Mutations in the SERPINA1 gene cause AAT deficiency. Without enough functional AAT, proteolytic enzymes destroy alveoli, leading to lung disease.

Incidence

• Prevalence: AATD occurs in approximately 1 in 3000–5000 live births in the US.

• Affected Population: People of northern European and Iberian descent are most affected.

Clinical Implications

• Disease Impact: AATD can cause both lung and liver disease.

• Age of Onset: Disease onset and first diagnosis usually occur between ages 30 to 45.

• Emphysema Risk: Patients are predisposed to early-onset emphysema.

• Treatment: Purified AAT replacement therapy helps prevent worsening of the condition.

Genetic Testing

• Testing Options: DNA testing and serum assays are available to measure the amount of AAT.

Genetics and COPD Development

• Genetic Factors: Some smokers develop COPD while others do not, suggesting a role for genetic factors.

• Environmental Interaction: Genetic-environment interaction means that two people with the same smoking history may display different outcomes; only one might develop COPD.

• Exposure to ETS: Genetics may also explain why individuals who never smoked but were exposed to environmental tobacco smoke (ETS) over long periods develop COPD.

• Genetic Marker: The “Z” allele of the AAT protein has been identified as a relevant genetic factor.

Alpha-1 Antitrypsin Deficiency Symptoms

• AATD is an autosomal recessive disorder affecting the lungs and liver, often going undetected until symptoms manifest. Smoking accelerates the disease process, with about 2% of COPD diagnoses in the US linked to undetected AATD. Genetic counseling may be recommended for those with AATD planning to have children.

Pathophysiology of COPD

Chronic Obstructive Pulmonary Disease (COPD) is characterized by chronic inflammation of the airways, lung parenchyma (respiratory bronchioles and alveoli), and pulmonary blood vessels. The defining feature of COPD is airflow limitation that is not fully reversible during forced exhalation. The main causes of this limitation include:

• Loss of Elastic Recoil: Contributing to airflow obstruction.

• Mucus Hypersecretion: Increases mucus production leading to obstruction.

• Mucosal Edema: Adds to airway narrowing.

• Bronchospasm: Results in further limitation of airflow.

Mechanisms

• COPD pathology develops from exposure to noxious particles and gases, like tobacco smoke and air pollution, leading to inflammation of central airways and peripheral airways, parenchymal destruction, and pulmonary vascular changes.

• Inflammatory cells (neutrophils, macrophages, lymphocytes) are predominant in COPD, and inflammatory mediators (e.g., leukotrienes, proinflammatory cytokines) significantly contribute to the disease process.

• Oxidative stress arising from inhaled pollutants exacerbates the inflammatory response and leads to structural lung changes.

Implications of the Inflammatory Process

• The inflammatory response causes tissue destruction and disrupts normal lung defense mechanisms. Enhanced inflammation can sometimes be genetically determined.

• The balance between proteases (which break down lung connective tissue) and antiproteases (which protect against degradation) is tipped in favor of destruction due to oxidant activity related to smoking, leading to further alveolar damage and loss of elastic recoil.

Airflow Limitation and Gas Exchange

• Airflow limitation primarily occurs in smaller airways. As these airways become obstructed, air becomes trapped in the lungs, leading to hyperinflation and a barrel-shaped chest.

• This further complicates respiration, resulting in dyspnea and limited exercise capacity.

• Problems with gas exchange may develop, causing hypoxemia and hypercapnia (increased CO2), especially in severe COPD cases.

Chronic Bronchitis and Mucus Production

• Chronic bronchitis results in persistent mucus production due to increased numbers of goblet cells and enlarged submucosal glands, causing chronic productive cough. Not all COPD patients will exhibit excess sputum production.

Pulmonary Vascular Changes

• Mild to moderate pulmonary hypertension can occur due to vasoconstriction of small pulmonary arteries in response to hypoxia and structural changes in the vessel walls, potentially leading to right heart failure.

Systemic Effects

• Chronic inflammation associated with COPD may contribute to other health issues such as osteoporosis and diabetes. As the disease progresses, a range of abnormalities can worsen, leading to devastating consequences for lung function and systemic health.

Classification of COPD

Chronic Obstructive Pulmonary Disease (COPD) is classified based on the severity of airflow limitation using the FEV1/FVC ratio and FEV1 results:

Clinical Manifestations

• Symptom Development: The manifestations of COPD typically develop slowly. A clinical diagnosis of COPD should be considered in any patient with chronic cough, sputum production, dyspnea, and a history of exposure to risk factors (e.g., tobacco smoke, occupational dusts).

• Coughing: A chronic intermittent cough is often the first symptom, which patients may dismiss, associating it with smoking or environmental exposure. The cough may be productive, and significant airflow limitation may exist without cough or sputum.

• Dyspnea: Dyspnea is progressive, usually occurring with exertion and being present every day. Patients report chest heaviness, gasping, increased effort to breathe, and air hunger, often rationalizing their symptoms with statements like "I’m getting older" or "I’m out of shape." They typically seek medical care when dyspnea becomes severe.

• Late Stage Symptoms: In late stages, dyspnea may be present at rest, and the patient must work harder to breathe. As alveoli become overdistended and air is trapped, the diaphragm flattens, reducing effective abdominal breathing. Patients may rely on chest breathing, which becomes inefficient over time.

• Other Symptoms: Wheezing and chest tightness may be present, varying throughout the day or from day to day. Patients with advanced COPD may experience fatigue, weight loss, and anorexia, with fatigue particularly impacting ADLs.

• Physical Examination Findings: Prolonged expiratory phase, decreased breath sounds or wheezes in lung fields, increased anteroposterior diameter ("barrel chest"), and potential use of the tripod position for breathing support.

• Hypoxemia and Polycythemia: Over time, hypoxemia (PaO2 <60 mm Hg or O2 saturation <88% on room air) may develop alongside hypercapnia (PaCO2 >45 mm Hg), leading to bluish-red skin color from polycythemia and cyanosis due to increased red blood cell production as a compensation for chronic hypoxemia. Hemoglobin concentrations may rise significantly or be low due to chronic anemia.

Drug Therapy for Asthma and COPD