Atelectasis, Pulmonary Edema, ALI and ARDS Flashcards
What does atelectasis refer to?
Either incomplete expansion of the lungs or a collapse of the lungs after being inflated.
What are the three types of atelectasis and explain each one?
- Resorption: complete obstruction of an airway leading to reduced lung expansion.
- Compression: Fluid, tumor, or air accumulate within the pleural cavity and compress the lungs.
- Contraction: fibrosis over the lung stops it from being able to expand.
What is a major difference between resorption and compression atelectasis?
In resorption, mediastinum shifts towards the collapsed lung and in compression the mediastinum shifts away from the collapsed lung.
How do we define pulmonary edema on histo?
Pink material in alveolar spaces
What are the two big picture causes of PE?
Hemodynamic problems or direct injury to the capillaries leading to increased permeability
When we say hemodynamic problems causing PE, what are we talking about?
We are talking about increasing hydrostatic pressure or decreasing oncotic pressure.
3 common causes of increasing hydrostatic pressure?
Left sided heart failure (most common), volume overload and pulmonary vein obstruction
What are 3 common causes of decreasing oncotic pressure?
Low albumin, nephrotic syndrome, and liver disease
Histologically, what are the cells we see with Pulmonary Edema?
Hemosiderin laden macrophages or heart failure cells. These are macrophages that have taken up RBCs.
What are 4 causes of injury to the alveolar wall that will lead to pulmonary edema?
Bacterial infection, sepsis, smoking, and aspiration
How do we define acute lung injury? What are we essentially saying this is?
we are essentially saying this is pulmonary edema not caused by cardiac failure. So a good definition is sudden hypoxemia and bilateral lung infiltrates in the absence of cardiac failure.
So then what is ARDS essentially then?
A very severe manifestation of ALI.
What is the classic histo manifestation of both ALI and ARDS?
Diffused alveolar damage
More than half of ARDS cases are associated with what 4 conditions?
Sepsis, pulmonary infections, gastric aspiration, and mechanical trauma (including head injuries).
What PaO2/FIO2 is required for ALI and ARDS?
Less than 300 and less than 200
What are the 4 stages of the pathogenesis of ARDS?
- Endothelial activation due to injury releasing a whole bunch of nonsense
- Adhesion of neutrophils to the damaged endothelium and then they exit to the alveoli
- Accumulation of interstitial and intraalveolar fluid
- Resolution of the injury by TGFB and PDGF causing alveoli to become fibrotic
What is basically at the heart of the patho of ARDS?
Cycle of inflammation and endothelial damage.
What is a characteristic feature of ARDS/ALI and what exactly is it?
Formation of a hyaline membrane within the alveoli. It is the combo of protein rich edema with necrotic pneumocytes.
What 3 things does she want us to know that equal hyaline membranes?
Edema + proteins (like fibrin) + cell debris
What are two other complications because of the patho of ARDS besides the diffuse alveolar damage?
Because the type 2 cells are getting their butts kicked, you have stiff lungs and collapsed alveoli because of a drop in surfactant. Also, you are not exchanging gas as well so the ventilation/perfusion ratio is jacked. You are still sending blood, but not adding oxygen.
How do they like to break up ARDS into stages? What is happening in each one?
- Exudative: edema, hyaline membranes and neutrophils
- Proliferation: tons of fibroblasts and early fibrosis
- Fibrotic: extensive fibrosis and loss of alveolar cells
Talk about an important note about the two options after the second stage?
It can either resolve completely and the lung will have normal tissue and cells or there will be complete fibrosis to the area and the damage will be irreversible.
What are the two clinical symptoms of ALI?
Dyspnea and tachypnea
When it crosses over into ARDS, what symptoms are we seeing now?
Cyanosis, hypoxemia, respiratory failure and the appearance of bilateral infiltrates on X ray that they call “white out”
How do we define Acute Interstitial Pneumonia?
It is essentially widespread ALI without a known cause or etiology
