Notes on Pulmonary Emphysema Lecture
Introduction to Lung Compliance
- Lung Compliance: A measure of distensibility of the lungs.
- Increased compliance can seem positive (more distensible lungs), but can lead to problems:
- Loss of elastic recoil during expiration.
- Narrowing of airways, preventing effective expiration.
- Leads to over-distension of lungs and lung parenchyma damage.
Definition of Emphysema
- Emphysema: Over-distension of lung tissue with air, specifically pulmonary emphysema.
- Begins with chronic airway obstruction, leading to:
- Damage to bronchi, bronchioles, and alveoli.
- Damage to pulmonary capillaries.
- Eventually affects the right side of the heart due to circulation burden.
Pathophysiology of Emphysema
- Chronic Obstructive Disease: Starts with chronic obstruction of airways.
- Progressive Damage:
- Airways → Alveoli → Pulmonary Capillaries
- 50-80% of alveolar walls can be destroyed.
- Consequences:
- Increased lung distension.
- Reduced elastic recoil.
Etiology of Emphysema
- Common Causes:
- Chronic smoking.
- Chronic infections.
- Mechanism of Damage:
- Irritation of airways leads to deranged normal defense mechanisms.
- Cilia paralysis due to nicotine, resulting in:
- Mucus accumulation and plugging.
- Increased risk of infection due to inhibited alveolar macrophages.
Increased Airway Resistance
- Obstruction makes expiration difficult:
- Inspiration is easier due to negative intrathoracic pressure.
- Early airway closure during expiration leads to air trapping in the alveoli.
Features of Emphysema
- Barrel-shaped Chest: Due to over-distension of lungs.
- Functional Residual Capacity (FRC): Increased from normal 2.5-3L to 7-8L.
Lung Compliance in Emphysema
- Increased Compliance: From normal 200 ml/cm H2O to 900 ml/cm H2O.
- Elastic Recoil Decreases: Challenges in expiration due to loss of elastic recoil.
Impacts on Lung Function
- FEV1 Decrease: Expected due to airway obstruction.
- Diffusing Capacity Decrease: Damaged alveolar walls and capillaries.
- Carbon Dioxide Buildup: Leads to respiratory acidosis, compensatory bicarbonate increase.
- Physiologic Shunts: Poor ventilation in some areas and wasted ventilation in others.
Consequences of Pulmonary Capillary Destruction
- Increased Pulmonary Vascular Resistance: Leads to pulmonary hypertension.
- Right-sided Heart Failure: Caused by increased workload and blood viscosity from secondary polycythemia due to hypoxia.
Clinical Presentation
- Emphysematous Patients:
- Take short breaths (high compliance allows easy intake but difficulty in expulsion).
- Appearance: Pink skin, hence called "Pink Puffers".
- Contrast with chronic bronchitis patients, known as "Blue Bloaters".
Six E's of Emphysema
- Edematous Airways: Inflammation leading to narrow airways.
- Excess Mucus Production: Mucus plugs formed due to impaired clearance.
- Early Closure of Airways: Difficulty in expiration.
- Elastic Recoil Decrease: Challenges in airway function.
- Equal Pressure Point Shift: Shifted downward affecting expiration.
- Emphysematous Damage: Overall damage leading to the disease progression.
This structure presents a clear and organized approach to the lecture content, highlighting the key points and concepts regarding pulmonary emphysema.