COPD Flashcards
Obstructive Lung Disease Definition
Definition: A broad category of diffuse lung disease characterized by increased resistance to airflow, caused by obstruction of airways.
- Remember, obstruction of airways may occur at any level or combination of levels, from the large bronchi all the way to the terminal bronchioles.
- Over time, this usually results in increased total lung volume due to air trapping behind the obstructions.
- Obstruction does not mean complete closing off or plugging of airways; the term “airflow limitation” is more accurate.
4 major Obstructive Lung Diseases
- Emphysema***
- Chronic bronchitis***
- Bronchiectasis
- Asthma
***NOTE! Emphysema and chronic bronchitis are often clinically grouped together and referred to as “chronic obstructive pulmonary disease” (COPD), because they often occur in combination, with features that often overlap in individual patients.
COPD Definition
A clinical syndrome characterized by chronic airflow obstruction due to emphysema and chronic bronchitis, usually occurring in combination (the relative severity of each component may vary).
Emphysema and Chronic Bronchitis
Emphysema and chronic bronchitis are both caused primarily by cigarette smoking, and they produce similar symptoms and functional abnormalities. Only structural analysis of the lungs (and sophisticated physiologic and radiologic analysis) separates them accurately. For practical clinical purposes, they are often lumped together.
Nonspecific Symptoms of COPD
Sometimes cough, sometimes sputum production, typically shortness of breath; most characteristic is slowing of forced expiration
“Blue Bloaters”
Patients with predominantly chronic bronchitis are often younger, have peripheral cyanosis, may develop cor pulmonale (right heart failure) more readily, and may have less radiographic evidence of emphysema. A nickname for these patients is “blue bloaters.”
“Pink Puffers”
Patients with predominantly emphysema tend to be older, have a ruddy complexion because of secondary polycythemia (increased red blood cell mass), develop cor pulmonale late if at all, and appear to have larger lungs. A nickname for these patients is “pink puffers.”
Emphysema Definition
- Emphysema is a condition of the lung characterized by abnormal, permanent enlargement of the air spaces distal to the terminal bronchiole, accompanied by destruction of alveolar walls, without obvious fibrosis
- It is believed that this condition (in its pure form) causes obstruction of airflow not because of narrowing of airways (as occurs in chronic bronchitis), but because the natural elastic recoil of the lung during exhalation is reduced when lung tissue has been destroyed and small airways collapse.. [*NOTE: Most COPD patients have both emphysema and chronic bronchiolitis, so obstruction results from a combination of diminished elastic recoil and airway narrowing, occurring simultaneously.]
Emphysema [is or is NOT] the same as hyperinflation or overdistension of the lungs, a reversible change characterized by acute dilatation of air spaces without destruction of lung tissue.
Emphysema is NOT the same as hyperinflation or overdistension of the lungs, a reversible change characterized by acute dilatation of air spaces without destruction of lung tissue.
2 Types of Emphysema
- centriacinar
- panacinar
Centriacinar Emphysema
- Characterized by destruction of alveolar walls that is accentuated in the center of the acinus.
- Since 4-9 acini make up a lobule, anything centriacinar is more or less centrilobular, too.
- Dilated air spaces 1-10 mm in diameter.
- Gross appearance is discrete holes in the lung, without a discernible wall, surrounded by normal lung tissue, often more prominent in the upper lung zones.
- Microscopically, lesions are round and have very thin walls, with an approximate thickness of a normal alveolar septum, but with far fewer protruding alveolar septa.
- Arises from injury to respiratory bronchioles; may see remnants of these.
- Similar lesion in coal workers associated with black dust deposits.
- 20 times more common than panacinar emphysema.
Pacinar Emphysema
- Characterized by destruction of alveolar walls that is diffuse, involving the entire acinus and therefore also involving the whole lobule.
- Typically associated with α-1-antitrypsin deficiency.
- All air spaces enlarged 1-10 mm.
- Gross appearance is confluent areas of enlarged holes; may involve lung diffusely or be more prominent in lower lung zones.
- Microscopically, lesions have smooth, thin walls without many protruding septa.
- Far less common than centriacinar emphysema.
Bulla
A bulla is an emphysema lesion greater than a centimeter, and is usually subpleural. Bullae may co-exist with other types of emphysema, or be the only kind of emphysema in the lung.
Bleb
A “bleb” is an air-filled lesion within the visceral pleura that is often confused with a bulla. A pleural bleb is NOT a bulla. A pleural bleb is NOT emphysema.
Paraseptal Emphysema
Involves the distal acinus (near the interlobular septum), often in subpleural lung zones. This form of emphysema is rare, but sometimes is a cause of “spontaneous” pneumothorax.
Irregular Emphysema
When lung injury (of any type) results in a scar, irregular emphysema sometimes develops immediately adjacent to that scar. Generally irregular emphysema is clinically unimportant.
α-1-Anti-Trypsin (α-1-AT) Theory of Emphysema Pathogenesis
- Major serum antiprotease is α-1-AT
- Absence of α-1-AT results in early emphysema
- α-1-AT neutralizes elastase secreted by neutrophils
- Elastin is skeleton of the lung
- Pi locus on chromosome 14 specifies α-1- AT; codominant
- PiMM is 95% of us: normal serum α-1-AT
- PiZZ is < 1%: almost no serum α-1-AT
- Smokers have more neutrophils in their lungs
- Smokers get emphysema from imbalance of of neutrophil elastase and α-1-AT
Chronic Bronchitis Definition
Chronic bronchitis is a condition of the lung characterized by chronic inflammation of airways, especially small airways (bronchioles), that leads to luminal narrowing and obstruction of airflow.
Chronic Bronchitis
- Especially involves non-cartilaginous, non-alveolated airways in the range of 0.3-2.0 mm.
- Although the term chronic bronchitis is very commonly used, a more accurate term would be “chronic bronchiolitis”, as this disease primarily affects small airways (bronchioles) rather than large airways (bronchi).
- An alternative (and also more accurate) term that is commonly used clinically for chronic bronchitis is small airway disease. (*NOTE: “Airway” is also sometimes used in its pleural form, i.e. “small airways disease”, to emphasize the diffuse nature of this process.)
- Changes include fibrosis, chronic inflammation, muscular hypertrophy, pigment accumulation, mucous plugging, and epithelial abnormalities in the small bronchioles.
- Caused by cigarette smoking.
- Clinically, this disorder is extremely difficult to separate from emphysema and they often occur in combination; therefore, they are often lumped together under the umbrella term “COPD”.
Types of Chronoc Bronchitis
• Simple chronic bronchitis: productive cough (clinical) •
Chronic obstructive bronchitis: chronic bronchitis plus small airways disease/bronchiolitis
• Asthmatic bronchitis: chronic bronchitis plus asthma
Small Airways Disease aka Chronic Bronchitis
- The “obstruction” in chronic obstructive bronchitis
- Caused by smoking
- Basically a bronchiolitis with mucous plugs, inflammation, and fibrosis
- Usually coexists with emphysema
- …airflow obstruction in COPD is primarily irreversible and is caused by disease of small airways, which is due in part to the effects of inflammation in those airways and in part to the loss of alveolar septal tethering of small airways that accompanies the destructive changes of emphysema.
All COPD is due to obstruction at the small airways level
- INTRINSIC: small airways disease (fibrosis, mucous plugs, inflammation)
- EXTRINSIC: dynamic collapse of small airways in expiration due to lack of support
Asthma Definition
Asthma is a condition of the lung characterized by 1) chronic inflammation of airways, 2) hyperreactivity of airways (increased responsiveness to various stimuli), and 3) episodic and usually reversible bronchoconstriction. Most asthma is associated with atopy, which is the tendency to generate excess IgE in response to external allergens.
3 Major Typs of Extrinsic Asthma
- Atopic (Allergic) Asthma
- Drug Induced Asthma
- Occupational Asthma
Atopic Asthma
- Initiated by a type I hypersensitivity reaction to an environmental allergen (occurring within minutes of exposure): IgE-coated mast cells bind allergen, release leukotrienes, histamine, acetylcholine, and other cytokines; IL-5 attracts eosinophils.
- Late-phase reaction (hours later): Neutrophils are recruited to irritated airways, major basic protein from eosinophils damages epithelium; the result is bronchoconstriction.
- Often a familial disease; complicated polygenic inheritance with variable penetrance; associated with allergic rhinitis, eczema (inflammatory skin lesions), and urticaria (hives).
- Onset usually in childhood, but often recurs in adult life
Drug Induced Asthma
Asthma induced by exposure to various drugs, especially aspirin.
Occupational Asthma
Asthma induced by occupational exposure to various chemicals.
Intrinsic (Non atopic) Asthma
- Often triggered by viral infections.
- IgE levels are often elevated compared to normal individuals of the same gender and age.
- Onset in adult life is more typical.
Gross Pathology of Asthma
Obstructive mucous plugs in bronchi and hyperinflation of lungs due to mucous plugs that enable air to enter during inhalation, but trap air during exhalation.
Microscopic Pathology of Asthma
- Basement membrane thickening by deposition of collagen under basement membrane (sometimes called airway remodeling).
- Eosinophilic inflammatory infiltrates within bronchial walls.
- Mucous plugs in airways.
- Variable smooth muscle enlargement, bronchial gland enlargement, and chronic inflammation within airways.
Complications of Asthma
- Sudden death, usually from status asthmaticus (an unrelenting asthma attack for days to weeks).
- Pulmonary hypertension with cor pulmonale (right heart failure).
- Bronchiectasis (abnormal, permanent dilatation of bronchi).
The Acinus (pl. Acini)
- Functional unit of the lung
- All the parenchyma subtended by (distal to) the last nonalveolated bronchiole (terminal bronchiole)
- 5-9 acini make a lobule
What Emphysema is NOT
- Hyperinflation
- Overdistension
- Honeycombing (fibrosis)
- Bleb
