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Flashcards in Obstructive & Restrictive Lung Disease Deck (66)
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1

Atelectasis

Loss of lung volume caused by inadequate expansion of airspaces
Results in shunting of inadequately oxygenated blood from pulmonary arteries to the pulmonary veins
-Ventilation-perfusion imbalance
-Hypoxia

2

Atelectasis 3 forms

Resorption Atelectasis
Compression Atelectasis
Contraction Atelectasis

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Resorption Atelectasis

Obstruction prevents air from reaching distal airways
Most common cause is a mucous or mucopurulent plug in a bronchus
-Postoperatively; also asthma, bronchiectasis, chronic bronchitis, or aspiration of a foreign body

4

Compression Atelectasis

Mechanical collapse of the lung
Usually associated with accumulation or fluid, blood, or air in the pleural cavity
Elevated diaphragm: Bedridden, ascites, surgery

5

Contraction Atelectasis

Caused by fibrotic changes
Hamper expansion or increase elastic recoil

6

Acute Lung Injury

Encompasses a spectrum of pulmonary lesions that can be initiated by numerous conditions
Clinically
-Acute onset of dyspnea
-Hypoxemia
-Bilateral pulmonary infiltrates on radiographs
-No clinical evidence of primary left-sided heart failure
An example of non-cardiogenic pulmonary edema
Most severe manifestation of ALI is Acute Respiratory Distress Syndrome (ARDS)

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Acute Respiratory Distress Syndrome

ARDS is a clinical syndrome caused by diffuse alveolar capillary and epithelial damage
-Rapid onset of life-threatening respiratory insufficiency
-Cyanosis
-Severe hypoxemia refractory to oxygen therapy
-May progress to multisystem organ failure
May be caused by direct or indirect injury to the lung
Histological manifestation of ARDS is known as Diffuse Alveolar Damage

8

ARDS Pathogenesis

The blood-air barrier is compromised by endothelial injury, epithelial injury, or most commonly both
-Leads to increased vascular permeability and alveolar flooding, loss of diffusing capacity, and widespread surfactant abnormalities
Lung injury is caused by an imbalance of pro-inflammatory and anti-inflammatory mediators
-Neutrophils are thought to have an important role in the pathogenesis of ARDS

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ARDS clinical

Mortality rate: 60%
Poor prognosis: Advanced age, bacteremia (sepsis), multisystem failure
Chronic sequelae: may develop diffuse interstitial fibrosis and have continued compromise of respiratory function
In most patients who survive normal respiratory function returns within 6-12 months

10

Obstructive disease (airway disease)

Limitation of airflow resulting from an increase in resistance caused by partial or complete obstruction at any level

11

Restrictive disease

Reduced expansion of lung parenchyma accompanied by decreased total lung capacity

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Major diffuse obstructive disorders

Emphysema, chronic bronchitis, bronchiectasis, and asthma
Hallmark is decreased expiratory flow rate
Measured by FEV1
Obstruction is the result of anatomic narrowing or decreased elastic recoil

13

Diffuse restrictive diseases

FEV1 is normal or proportionally reduced
Causes
-Chest wall disorders in the presence of normal lungs
*Obesity, pleural disease, neuromuscular disorders
-Acute or chronic interstitial lung diseases
*Acute: ARDS
*Chronic: pneumoconioses, idiopathic pulmonary fibrosis, infiltrative conditions (e.g., sarcoidosis)

14

Obstructive Pulmonary Disease

Emphysema and chronic bronchitis can exist one without the other, but they usually coexist
-Both have a common trigger—cigarette smoking, especially long-term, heavy tobacco exposure
Often emphysema and chronic bronchitis are grouped together clinically as Chronic Obstructive Pulmonary Disease (COPD)
-Affects >10% of the adult population in the US
-Fourth leading cause of death in the US

15

Emphysema

Abnormal permanent enlargement of the airspaces, distal to the terminal bronchioles, accompanied by destruction of their walls without obvious fibrosis
Emphysema is classified by its anatomic distribution within the lobule
-Centriacinar, panacinar, distal acinar, and irregular
-Only the first two cause clinically significant airway obstruction
-Centriacinar is 20 times more common than panacinar

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Centriacinar (Centrilobular) Emphysema

Central or proximal part of acini involved; distal alveoli spared
More common and severe in the upper lobes
In severe cases, the distal acinus can become involved
Most commonly seen as a consequence of cigarette smoking

17

Panacinar (Panlobular) Emphysema

Acini uniformly enlarged from respiratory bronchiole to terminal blind alveoli
More common in the lower lung zones
Occurs in α1-antitrypsin deficiency (genetic deficiency)

18

Distal Acinar (Paraseptal) Emphysema

Distal acinus involved; proximal part normal
Most striking near pleura, along lobular septa, and margins of lobules
Adjacent to areas of fibrosis, scarring, or atelectasis
More severe in upper half of lungs
Sometimes spaces merge and further enlarge into bullae
Associated with spontaneous pneumothorax in young people

19

Irregular Emphysema

Acinus is irregularly involved
Associated with scarring
Most common form of emphysema
-Clinically asymptomatic

20

Emphysema Pathogenesis

Current opinion favors two critical imbalances
-Protease-antiprotease imbalance
-Oxidant-antioxidant imbalance
Almost always coexist
-Additive effect in producing tissue damage
Protease-antiprotease imbalance hypothesis
-Genetic deficiency of α1-antitrypsin has a marked tendency to develop emphysema that is compounded by cigarette smoking

21

Protease-antiprotease imbalance hypothesis

Neutrophils are normally sequestered in the pulmonary capillaries; a few gain access to the alveolar spaces
Any stimulus that increases number of leukocytes or release of protease containing granules increases proteolytic activity
With low levels of α1-antitrypsin, elastic tissue destruction is unchecked resulting in emphysema

22

Cigarette smoking contributes to both protease-antiprotease and oxidant-antioxidant imbalance hypotheses

Neutrophils and macrophages accumulate in alveoli
Neutrophils are activated
Macrophage elastase activity is enhanced
Tobacco smoke contains abundant reactive oxygen species
Activated neutrophils generate reactive oxygen species
Oxidative injury inactivates native antiproteases

23

Clinical of “pure” emphysema

Dyspnea is usually first symptom; steadily progressive
Weight loss
Reduced FEV1

24

Emphysema Classic presentation

Barrel-chested and dyspneic, prolonged expiratory interval, sitting hunched forward squeezing the air out of lungs with each breath
Severe airspace enlargement and low diffusing capacity, dyspnea and hyperventilation is prominent until very late in the disease, gas exchange is adequate and blood gases are near normal
Referred to as “Pink puffers” (see later picture)

25

Emphysema clinical course

Secondary pulmonary hypertension develops gradually
-Hypoxia-induced vascular spasm
-Loss of pulmonary capillary surface area
Death
-Pulmonary failure
-Right-sided heart failure

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Emphysema That’s Not Emphysema

Compensatory emphysema
-loss of parenchyma
Obstructive overinflation
Bullous emphysema
Mediastinal (interstitial) emphysema

27

Chronic Bronchitis clinical diagnosis

Persistent productive cough for at least 3 months in at least 2 consecutive years
Caused by cigarette smoking and air pollutants

28

Chronic Bronchitis 3 forms

Simple chronic bronchitis
-Airflow not obstructed
Chronic asthmatic bronchitis
-Hyperresponsive airways with intermittent bronchospasm and wheezing
Chronic obstructive bronchitis
-Chronic outflow obstruction usually with associated emphysema
-Heavy cigarette smokers

29

Chronic Bronchitis pathogenesis

Hypersecretion of mucus is a distinctive feature
-Cigarette smoking and air pollutants induce:
*Hypertrophy of mucous glands in the trachea and bronchi
*Marked increase in goblet cells in smaller bronchi and bronchioles
*Inflammation and infiltration by CD8+ T cells, macrophages, and neutrophils (eosinophils are lacking unless asthmatic bronchitis)
Airflow obstruction is due to peripheral involvement
-Small airway disease
*Goblet cell metaplasia with mucous plugging, inflammation, and bronchiolar wall fibrosis
*Causes early and mild airflow obstruction
-Coexistent emphysema
*Cause of significant airflow obstruction
Microbial infection has a secondary role
-Maintains inflammation
-Exacerbates symptoms

30

Chronic Bronchitis clinical

Prominent cough with production of sputum
With chronic outflow obstruction,
Hypercapnia, hypoxemia, cyanosis
Secondary pulmonary hypertension and right-sided heart failure
Often seek medical attention when CHF develops
Referred to as “Blue bloaters” (see picture later)
Recurrent infections and respiratory failure are constant threats