RS14 - Respiratory Diseases Part I

What causes respiratory distress syndrome of the newborn (RDS)?

Insufficient surfactant production by type II pneumocytes.

In RDS, what happens to the alveoli because of surfactant deficiency?

The alveoli collapse.

In RDS, what lines the collapsed alveoli microscopically?

Granular debris mixed with fibrin, forming hyaline membranes.

Why is RDS also called "hyaline membrane disease"?

Because hyaline membranes line the alveoli.

In RDS, why does hypoxia occur?

Hyaline membranes block gas exchange.

What is the most common cause of death in premature infants?

Respiratory distress syndrome (RDS).

What is the most important risk factor for RDS?

Prematurity, especially before 28 weeks.

What birth weight increases the risk of RDS?

Less than 2.5 kg.

How does maternal diabetes affect the risk of RDS?

It increases the risk.

How does being a second twin affect the risk of RDS?

It increases the risk.

What are the classic clinical features of RDS?

Cyanosis, rapid breathing, and hypotension.

What is sudden infant death syndrome (SIDS)?

Sudden, unexpected death of an apparently healthy infant that remains unexplained after autopsy and investigation.

At what age is SIDS most common?

Between 2 and 4 months of age.

What type of dysfunction is suspected in SIDS?

Autonomic dysfunction.

What sleep abnormality may contribute to SIDS?

Abnormally prolonged sleep apnea.

What are other names for SIDS?

Crib death and cot death.

What sleep position increases the risk of SIDS?

Sleeping on the stomach.

What maternal behaviors increase the risk of SIDS?

Smoking or drug use during pregnancy.

What infections during pregnancy increase the risk of SIDS?

Maternal STD or UTI.

What enzyme deficiency has been possibly linked to SIDS?

Low levels of butyrylcholinesterase.

What conditions must be ruled out before diagnosing SIDS?

Homicide, metabolic disease, sepsis (meningitis), and congenital heart disease.

What was the goal of the Safe to Sleep campaign?

To encourage placing babies on their back or side to sleep.

How effective was the Safe to Sleep campaign?

It reduced SIDS cases by up to 50%.

What is asthma?

Episodic, reversible bronchoconstriction caused by increased responsiveness of the tracheobronchial tree to stimuli.

What underlying process plays a major role in asthma?

Persistent bronchial inflammation.

What are the classic clinical symptoms of asthma?

Cough, wheezing, and dyspnea.

What percentage of adults have asthma?

About 5%.

What percentage of children have asthma?

About 7%.

Is the frequency of asthma increasing or decreasing?

Increasing.

What inflammatory mediators are released in all types of asthma?

Histamine and cytokines.

What are the main effects of mediator release in asthma?

Inflammation, hypersecretion of mucus, diminished ciliary activity, and bronchospasm.

What happens to airway smooth muscle in asthma?

It undergoes hypertrophy and contraction.

What happens to goblet cells in asthma?

Goblet cells undergo hyperplasia.

What happens to mucous glands in asthma?

They enlarge.

What fills the bronchi and bronchioles in asthma?

Thick mucus.

What type of inflammatory cells are commonly seen in asthma?

Eosinophils.

What type of hypersensitivity reaction is extrinsic (atopic) asthma?

Type I hypersensitivity reaction.

What is atopy?

A predisposition to developing hypersensitivity against common allergens.

Is extrinsic asthma the most common form of asthma?

Yes.

What immunoglobulin is elevated in extrinsic asthma?

IgE.

At what age does extrinsic asthma typically begin?

Childhood or teenage years.

Does extrinsic asthma often show seasonal variation?

Yes.

Is there usually a personal or family history of allergies in extrinsic asthma?

Yes.

What happens when an allergen cross-links IgE on mast cells in extrinsic asthma?

Mast cells degranulate.

What mediators are released from mast cells in extrinsic asthma?

Histamine, prostaglandins, and leukotrienes C4, D4, and E4.

What complement components can also trigger attacks in extrinsic asthma?

C3a and C5a.

What are the final airway effects of extrinsic asthma?

Edema, mucus hypersecretion, bronchoconstriction, and eosinophil-mediated inflammation.

What triggers intrinsic (non-atopic) asthma?

Non-allergic stimuli such as chemicals (e.g., aspirin), cold air, or infections.

Are IgE levels elevated in intrinsic asthma?

No, they are low to normal.

At what age does intrinsic asthma typically begin?

After age 30.

Is there usually a personal or family allergy history in intrinsic asthma?

No.

Does intrinsic asthma have a seasonal pattern?

No.

Are intrinsic asthma attacks intermittent or continuous?

Continuous.

What severe complication is more common in intrinsic asthma?

Status asthmaticus.

What neural pathway contributes to intrinsic asthma?

Vagus nerve-mediated reflexes affecting smooth muscle and mucous cells.

Do extrinsic and intrinsic asthma have different final airway effects?

No — both cause edema, mucus hypersecretion, bronchoconstriction, and inflammation.

What is status asthmaticus?

A severe asthma attack that does not respond to therapy.

How long can status asthmaticus last?

Hours to days.

Why can status asthmaticus be life-threatening?

It can cause fatigue, dehydration, shock, drug intoxication, and death.

What two diseases make up chronic obstructive pulmonary disease (COPD)?

Emphysema and chronic bronchitis.

What is the usual cause of both emphysema and chronic bronchitis?

Smoking.

Do emphysema and chronic bronchitis have the same pathogenesis?

No, but they often coexist.

What is emphysema?

Enlargement of airspaces distal to the terminal bronchiole with destruction of alveolar walls.

How does emphysema affect oxygen exchange?

It reduces surface area and decreases oxygen diffusing capacity.

What happens to alveolar walls in emphysema?

They are destroyed.

Why do patients with emphysema have difficulty exhaling?

Loss of elastic recoil prevents effective air expulsion.

What compensatory change occurs in emphysema?

Overinflation and hyperventilation.

What cardiac complication can result from emphysema?

Pulmonary hypertension leading to cor pulmonale.

Why are patients with emphysema called "pink puffers"?

They hyperventilate, maintaining relatively normal oxygenation, so they are not cyanotic.

What physical feature is common in "pink puffers"?

Barrel chest.

How does smoking contribute to emphysema?

It stimulates elastase release and inhibits α-1 antitrypsin.

What is the role of α-1 antitrypsin in the lungs?

It inhibits elastase.

What happens when α-1 antitrypsin is deficient?

Unopposed elastase destroys elastic fibers.

What genotype is associated with α-1 antitrypsin deficiency?

PiZZ.

Which type of emphysema accounts for about 75% of cases?

Centrilobular emphysema.

Which lung region is usually affected in centrilobular emphysema?

Upper lobes.

Who most commonly develops centrilobular emphysema?

Smokers.

Which type of emphysema is most associated with α-1 antitrypsin deficiency?

Panlobular emphysema.

Which lung region is more affected in panlobular emphysema?

Lower lobes.

What is the diagnostic definition of chronic bronchitis?

Productive cough on most days for at least 3 months per year for 2 or more years.

What is the primary pathologic feature of chronic bronchitis?

Excessive mucus production due to mucous gland hyperplasia.

What happens to ciliary function in chronic bronchitis?

It is impaired, reducing mucus clearance.

What type of epithelial change can occur in chronic bronchitis?

Squamous metaplasia.

What airway changes occur in chronic bronchitis?

Bronchospasm and bronchoconstriction.

What major cardiac complication can result from chronic bronchitis?

Cor pulmonale.

Why are patients with chronic bronchitis called "blue bloaters"?

Poor ventilation causes hypoxemia (blue), and cor pulmonale causes edema (bloated).

What characterizes restrictive lung diseases?

Lung stiffness and reduced expansion.

What is the end-stage outcome of restrictive lung diseases?

Fibrosis.

What does ARDS stand for?

Acute Respiratory Distress Syndrome.

What is diffuse alveolar damage (DAD)?

The morphologic counterpart of ARDS.

What causes hyaline membrane formation in DAD?

Damage to alveolar epithelial cells and inflammatory exudate.

What happens in the early phase of ARDS/DAD?

Pulmonary edema and high mortality (about 50%).

What happens in later phases of ARDS/DAD?

Fibrosis.

What does idiopathic mean in idiopathic pulmonary fibrosis?

The cause is unknown.

What are the main symptoms of idiopathic pulmonary fibrosis?

Progressive dyspnea and dry cough.

What is the typical outcome of idiopathic pulmonary fibrosis?

Most patients die within 1 to 20 years.

What type of disease is sarcoidosis?

A multi-system granulomatous disease.

What type of granulomas are seen in sarcoidosis?

Non-caseating granulomas.

Which populations are most affected by sarcoidosis?

People of African ancestry and patients under age 40.

What is the classic chest X-ray finding in sarcoidosis?

Bilateral hilar adenopathy.