Pulmonary Pathology Part 1 Flashcards
What are the requirements for normal fetal lungs to develop?
- Space in thoracic cavity
- Ability to inhale (chest wall must be able to move and enough material must be present to inhale)
What is the process of airway breathing?
- Larger airways conduct air to the terminal acinar units for proper gas exchange
Why does gas exchange occur in the terminal acinar units?
- There are thin walls with high vascularity
What is most of the lung volume made up of?
- Pulmonary parenchyma
What does the normal structure of the alveolar space consist of?
- Capillaries with associated endothelium
- Type 1 pneumocytes where gas exchange occurs
- Type 2 pneumocytes that produce surfactant and can replace type 1 pneumocytes during times of destruction
- Alveolar pores which allow aeration but also bacteria/cells/exudate to travel between cells
What are the alveolar pores of Kohn?
- Holes that allow the travel of small material like bacteria, cells, or exudate
What are some congenital pulmonary anomalies?
- Pulmonary hypoplasia
- Foregut cysts
- Congenital pulmonary adenomatoid malformation (CPAM/CCAM)
- Pulmonary sequestration
- Tracheoesophageal fistuila
What is pulmonary hypoplasia?
- Reduced space in the thoracic cavity causes the lungs to be underdeveloped
What is another congenital defect can cause pulmonary hypoplasia?
- Diaphragmatic hernia (viscera is taking up space in thoracic cavity)
What are some causes of pulmonary hypoplasia?
- Oligohydramnios (renal agenesis)
- Airway malformation (tracheal stenosis)
- Chest wall motion disorders
What is the mortality of pulmonary hypoplasia?
- Up to 95%
- If lung weight is <40%, immediate death occurs
What is a foregut cyst?
- A detached outpouching of foregut
Where is a foregut cyst typically seen?
- Along hilum and mediastinum
When are foregut cysts found?
- Often found incidentally, usually when there is complication
What are some complications of foregut cysts?
- Rupture
- Infection
- Airway compression
What is the cure for foregut cysts?
- Excision of the cyst
What is congenital pulmonary adenomatoid malformation (CPAM)?
- “Arrested development” of pulmonary tissue with formation of intrapulmonary cystic masses
Where are CPAMs found?
- They communicate with the tracheobronchial tree
How are CPAMs found?
- Fetal ultrasound
What is the mortality with CPAMs?
- Could be deadly due to hydrops or pulmonary hypoplasia
- Could be asymptomatic throughout childhood can get infected later in life
What are pulmonary sequestrations?
- Non-Functioning lung tissue that forms as an aberrant accessory “lung bud”
Where would a pulmonary sequestration typically be found?
- Region of the left lower lobe
What is a pulmonary sequestration typically characterized by?
- Lack of connection to the tracheobronchial tree
- Independent arterial supply
Are pulmonary sequestrations intralobar or extralobar? Why?
- Could be either
- Based on whether the budding occurs before or after the pleura is established
Who typically presents with an intralobar pulmonary sequestration (ILS)?
- Older children or adults
What are some characteristics of an ILS?
- May be difficult to detect due to being inside the lung lobe
- Lack of airway perfusion makes it susceptible to infection and abscess formation
Why can abscesses for in an ILS?
- Lack of O2 to the neutrophils
Who typically presents with an extralobar pulmonary sequestration (ELS) ?
- Presents after birth with other congenital anomalies (like cardiac or GI)
What are some characteristics of an ELS?
- Looks like a mini lung
- Has independent vessels, pleura, and possibly airways
- Comes to attention as mass lesions in the chest or abdomen
Do either the ILS or ELS have connections to the pulmonary vasculature or tracheobronchial tree?
- NO
What is atelectasis?
- Incomplete expansion of lung parenchyma
What are the three types of atelectasis?
- Resorption
- Compression
- Contraction
What is resorption atelectasis?
- Airway obstruction with gradual resorption of air reduces lung expansion
- Anything distal to obstruction is where the air is reabsorbed
What is compression atelectasis?
- Accumulated material in pleural cavity compresses the lung parenchyma (pneumo/hemothorax)
What is contraction atelectasis?
- Fibrotic or other innate restrictive process in the pleura or peripheral lung restricts lung expansion
What are some causes of pulmonary edema?
- “Pushing out” (increase in pressure)
- “Leaking out”
- Injury to alveolar wall
- Unsure mechanisms (neurogenic or high altitude)
What are some of the physiological mechanisms behind pulmonary edema?
- Increased hydrostatic pressure forces out fluid
- Decreased oncotic pressure loses fluid through equilibrium across a semipermeable membrane
Where would we see high altitude pulmonary edema?
- In people that went hiking in the mountains
- Most notoriously seen in people who climbed Everest and waited to stand on peak
What is seen on histology in pulmonary edema?
- Pink proteinaceous material in alveolar spaces due to congestion
What is seen in pulmonary edema due to heart failure?
- Microhemorrhage occurs in congested areas
- There are scattered hemosiderin-laden macrophages that accumulate
What are “heart failure cells”?
- Hemosiderin-laden macrophages due to their association with pulmonary congestion due to CHF
What is the definition of acute lung injury?
- Acute onset
- Hypoxemia
- Bilateral infiltrates
- No evidence of cardiac failure
What is the definition of acute respiratory distress syndrome?
- Worsening hypoxia
What is the definition of diffuse alveolar damage?
- Histologic manifestation of ARDS
What is seen in ARDS?
- Abrupt onset of symptoms
- Hypoxemia (PaO2/FiO2 <200)
- Bilateral infiltrates
- Non-cardiac in nature
What is the cellular process of ARDS?
- Endothelial activation
- Adhesion/extravasation of neutrophils
- Accumulation of intra-alveolar fluid and formation of hyaline membranes
- Resolution of injury
What are the components of hyaline membranes?
- Edema
- Fibrin
- Cell debris
What do hyaline membranes do to the aeration?
- Decreased aeration causing hypoxemia (decreased PaO2/FiO2)
What are the stages of progression in ARDS?
- Exudative
- Proliferative
- Fibrotic
What is the exudative phase of ARDS?
- Edema
- Hyaline membranes
- neutrophils
What is the proliferative phase of ARDS?
- Fibroblast proliferation
- Organizing pneumonia
- Early fibrosis
What is the fibrotic phase of ARDS?
- Extensive fibrosis
- Loss of normal alveolar architecture
What are the two paths that could occur after the proliferative phase in ARDS?
- Resolution
- Fibrosis
What happens in the resolution phase of ARDS?
- Restoration of normal cellular structure and function
What happens in the fibrosis phase of ARDS?
- Destruction and distortion of normal cellular structure
- Irreversible
What is the pathologic diagnosis of ARDS?
- Hyaline membranes
- Interstitial edema
- Epithelial necrosis
