Chronic bronchitis is a major type of Chronic Obstructive Pulmonary Disease (COPD), a progressive lung condition that affects breathing and oxygen exchange. It is marked by chronic inflammation of the bronchi, excessive mucus production, and cough that lasts for months to years. This condition often affects smokers and is commonly referred to as the “blue bloater” phenotype of COPD due to the classic bluish skin discoloration caused by hypoxia.
Understanding Chronic Bronchitis
Chronic bronchitis is clinically defined as:
“Cough with sputum production for at least 3 months in 2 consecutive years, in the absence of any other identifiable cause.”
Unlike asthma, which is reversible, chronic bronchitis causes irreversible narrowing of airways, resulting in airflow obstruction.
Pathophysiology: What Happens in the Lungs?
The main processes involved are:
- Hypertrophy and hyperplasia of mucus-secreting glands
- Goblet cell metaplasia
- Chronic inflammatory cell infiltration of the bronchial wall
- Impaired mucociliary clearance
- Air trapping and hyperinflation
These changes lead to mucus retention, increased airway resistance, recurrent infections, and eventual respiratory failure.
Signs and Symptoms of Chronic Bronchitis
Let’s decode the clinical features highlighted in the image and understand their physiological basis.
1. Blue Dusky Colour due to Cyanosis
This bluish discoloration of the skin and lips, especially visible on the fingers and around the mouth, is due to hypoxia (low blood oxygen).
- Cyanosis occurs when oxygen saturation drops below 85%.
- Chronic hypoxia stimulates increased production of deoxygenated hemoglobin, which gives a blue hue to skin and mucosa.
This characteristic symptom has earned patients with chronic bronchitis the nickname “blue bloaters”.
2. Recurrent Cough with Sputum Production
The hallmark of chronic bronchitis is a productive cough that brings up thick, sticky mucus (sputum).
- This results from excessive mucus production due to hyperplasia of goblet cells.
- Frequent respiratory infections further exacerbate sputum volume and viscosity.
Coughing becomes a daily event, often worst in the morning and aggravated by environmental irritants.
3. Hypoxia (Low Blood Oxygen Levels)
Due to mucus plugging and airflow obstruction, less oxygen reaches the alveoli, leading to low arterial oxygen levels (PaO₂).
- Hypoxia causes pulmonary vasoconstriction, which increases pulmonary artery pressure.
- Chronic hypoxia also stimulates erythropoiesis, resulting in polycythemia (increased hemoglobin), which thickens the blood.
4. Hypercapnia (↑pCO₂)
Inability to expel carbon dioxide leads to CO₂ retention.
- Normally, CO₂ diffuses out during exhalation.
- In chronic bronchitis, airway narrowing and air trapping prevent this, leading to hypercapnia.
This buildup causes:
- Headaches
- Lethargy
- Confusion
- Asterixis (flapping tremor)
5. Respiratory Acidosis
As CO₂ accumulates in the blood, it combines with water to form carbonic acid, lowering the blood’s pH and causing respiratory acidosis.
- Compensated by the renal retention of bicarbonate, but chronic acidosis can still impair metabolism.
6. Increased Hemoglobin (Hb)
In response to chronic hypoxia, the kidneys release erythropoietin, stimulating the bone marrow to produce more red blood cells.
- This compensatory polycythemia improves oxygen-carrying capacity but increases blood viscosity and clotting risk.
7. Increased Respiratory Rate
As oxygen levels drop and CO₂ rises, the brainstem respiratory centers stimulate an increase in breathing rate.
- This tachypnea is an attempt to compensate for impaired gas exchange.
8. Exertional Dyspnea
Even mild physical activity can trigger shortness of breath due to:
- Poor ventilation-perfusion matching
- Limited lung expansion from mucus obstruction
- Increased work of breathing
This limits exercise tolerance and worsens quality of life.
9. Increased Cigarette Smoking
Cigarette smoke is the most significant risk factor for chronic bronchitis.
- Toxins in smoke damage cilia, impairing mucus clearance.
- They also trigger chronic inflammation, fibrosis, and epithelial metaplasia.
Secondhand smoke, air pollution, and occupational exposure (e.g., coal dust, chemicals) are additional contributors.
10. Digital Clubbing
Prolonged hypoxia results in digital clubbing – a painless enlargement of the ends of fingers and toes.
- Mechanism: Chronic hypoxia increases vascular endothelial growth factor (VEGF), leading to soft tissue proliferation.
- Seen in many chronic respiratory and cardiac diseases.
11. Cardiac Enlargement
Due to increased pulmonary vascular resistance from hypoxia, the right side of the heart (especially the right ventricle) must pump harder.
- This leads to right ventricular hypertrophy, visible as cardiomegaly on chest X-ray.
12. Right-Sided Heart Failure (Cor Pulmonale)
Chronic bronchitis is a common cause of Cor Pulmonale, or right-sided heart failure due to lung disease.
Features:
- Raised jugular venous pressure (JVP)
- Peripheral edema
- Hepatomegaly
- Ascites
This complication is a major cause of mortality in advanced COPD patients.
Summary Table: Clinical Features of Chronic Bronchitis
| Feature | Mechanism | Clinical Relevance |
|---|---|---|
| Cyanosis | Hypoxia | Blue discoloration |
| Cough + Sputum | Mucus hypersecretion | Productive cough |
| Hypoxia | Impaired gas exchange | Fatigue, polycythemia |
| Hypercapnia | CO₂ retention | Headaches, confusion |
| Acidosis | High CO₂ → H⁺ ions | pH imbalance |
| ↑ Hb | Erythropoietin release | Blood thickening |
| ↑ RR | Respiratory compensation | Breathlessness |
| Exertional dyspnea | Poor oxygenation | Reduced stamina |
| Digital clubbing | Chronic hypoxia | Swollen fingertips |
| Cardiac enlargement | Pulmonary hypertension | Right heart strain |
| Right heart failure | Cor Pulmonale | Systemic edema |
Diagnostic Approach
1. History and Physical Examination
- Duration of cough
- Smoking history
- Daily sputum production
- Auscultation: Wheeze, rhonchi
2. Pulmonary Function Tests (PFTs)
- Decreased FEV₁/FVC ratio (<0.7)
- Increased residual volume
- Normal or slightly reduced DLCO
3. Chest X-ray
- Cardiomegaly
- Increased bronchovascular markings
- Flat diaphragm in advanced disease
4. Arterial Blood Gas (ABG)
- ↓ PaO₂
- ↑ PaCO₂
- ↓ pH (respiratory acidosis)
5. CBC
- Polycythemia (↑ Hb)
- Rule out infection (leukocytosis)
Complications of Chronic Bronchitis
| Complication | Description |
|---|---|
| Pulmonary hypertension | Due to chronic hypoxia-induced vasoconstriction |
| Cor Pulmonale | Right heart failure from lung disease |
| Recurrent pneumonia | Due to mucus stasis |
| Respiratory failure | Hypoventilation, hypercapnia |
| Secondary polycythemia | ↑ blood viscosity, thrombotic risk |
Treatment Strategies
1. Smoking Cessation
The single most effective intervention in preventing progression.
- Nicotine patches
- Behavioral therapy
- Bupropion/Varenicline
2. Bronchodilators
- Short-acting beta agonists (SABA): Salbutamol
- Long-acting beta agonists (LABA): Salmeterol
- Anticholinergics: Ipratropium, tiotropium
3. Inhaled Corticosteroids
Reduce inflammation in moderate-severe disease or frequent exacerbations.
4. Oxygen Therapy
Indicated when PaO₂ < 55 mmHg or SpO₂ < 88%.
- Prolongs life
- Prevents right heart failure
5. Antibiotics
During acute exacerbations, often triggered by infections.
- Common pathogens: Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis
6. Pulmonary Rehabilitation
- Exercise training
- Breathing exercises
- Education and nutrition counseling
Prevention
| Strategy | Benefit |
|---|---|
| Smoking cessation | Reduces inflammation and mucus |
| Flu and pneumococcal vaccination | Prevents exacerbations |
| Pollution control | Minimizes airway damage |
| Early treatment of infections | Prevents chronic inflammation |
Frequently Asked Questions (FAQs)
What is the main difference between chronic bronchitis and emphysema?
Chronic bronchitis affects airways with mucus overproduction, whereas emphysema involves alveolar destruction. Clinically, chronic bronchitis patients are "blue bloaters", and emphysema patients are "pink puffers".
Is chronic bronchitis reversible?
No. Chronic bronchitis causes irreversible damage, but progression can be slowed with early treatment and lifestyle changes.
Can non-smokers get chronic bronchitis?
Yes, due to:
- Passive smoking
- Air pollution
- Occupational exposures
- Genetic susceptibility
How is chronic bronchitis diagnosed?
Primarily through clinical history (chronic productive cough) and confirmed by spirometry, chest imaging, and exclusion of other causes.
Is chronic bronchitis contagious?
No, it is not contagious, but viral or bacterial exacerbations may be infectious.
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