Diffuse alveolar damage

Question 1

DAD is a form of lung disease resulting from what?

Answer 1

Capillary wall endothelial injury

Question 2

What is acute lung injury

Answer 2

Abrupt onset of hypoxemia and bilateral pulmonary oedema, in the abscence of cardiac failure (i.e non-cardiogenic)

Question 3

What is acute respiratory distress syndrome

Answer 3

Manifestation of severe ALI (Clinical syndrome of progressive respiratory insufficiency)

Question 4

The diffuse alveolar damage which disorders

Answer 4

Both pulmonary and systemic disorders

Question 5

List the pulmonary and systemic disorders caused by Diffuse alveolar damage

Answer 5

Diffuse pulmonary infections
Gastric aspiration
Mechanical trauma including head injuries
Physical trauma/ injury e.g. Near-drowing, inhaled irritants e.g. Smoke
Chemical injury e.g. Barbiturate overdose
Hematologic conditions e.g. Transfussion-associated lung injury
Miscellaneous conditions e.g. Pancreatitis, uraemia
If idioathic= acute interstitial pneumonia

Question 6

Explain the gross appearance of diffuse alveolar damage

Answer 6

The lungs are virtually airless, diffusely firm, and rubbery with a glistening appearance on cut section
Heavy firm red boggy lungs

Question 7

Clinical the DAD is known as what?

Answer 7

Acute respiratory distress syndrome

Question 8

Which one is caused by DAD
A. Hypoxemia
B. Hypoxia
C. Ketoacidosis

Answer 8

A. Hypoxemia

Question 9

The lung diffusing capacity for Carbon monoxide is ?

Answer 9

Reduced

Question 10

Which diseases causes the decreased in carbin monoxide

Answer 10

Diseases that affect the alveolar walls (DAD or emphysema) or the pulmonary capillary bed (Thromboembolism or vasculitis)

Question 11

Injury of pneumocytes and pulmonary endothelium initiates a cycle of what?

Answer 11

Increasing inflammation and pulmonary damage that impairs alveolar gas exchange

Question 12

The hypoxemia is exacerbated by?

Answer 12

Ventilation-perfusion mismatch, as the lesions are not evenly distributed.

Question 13

What is Endothelial activation in DAD.

Answer 13

Early event
Can occur primarly as a response to circulating inflammatory mediators in severe tissue injury or sepsis, or secondary to pneumocyte injury that is sensed by resident alveolar macrophages which then secrete mediators.

Question 14

List examples of mediators that are secreted in Endothelial activation

Answer 14

TNF that act on the endothelium

Question 15

Explain the adhesion of neutrophils to activated endothelium and extravasation into interstitium and alveoli?

Answer 15

Neutrophils then degranulate and release inflammatory mediators and neutrophil extracellular traps, setting up the viscous cycle of inflammation and lung damage

Question 16

Explain what happens when there is accumulation of intra-alveolar fluid and formation of hyaline membrane?

Answer 16

Occurs as the endithelial activation and injury causes leaky ulmonary capillaries. Surfactant abnormalities also occurs due to damaged Tye II alveolar pneumocytes. Hyaline membrane then form as a result of organization of the protein-rich oedema fluid and dead alveolar eithelial cells

Question 17

Explain resolution of injury

Answer 17

If the inflmmatory stimulus is removed, macrophages remove intra-alveolar debris and secrete fibrogenic cytokines. e.g. TGF-Band PDGF, stimuating fibroblast growth and collagen deposition, resulting in fibrosis of alveolar walls. Residual type II pneumocytes proliferate to replace type I pneumocytes, and injured capillary endothelium proliferates to restore the endothelium

Question 18

Explain the microspic appearance of DAD

Answer 18

Congestion, interstitial and intra-alveolar oedema, inflammation, fibrin deposition and hyaline membrane lining alveolar walls (fibrin-rich).

Question 19

Oedema fluid is mixed with what in DAD?

Answer 19

Degenerating necrotic epithelial cells

Question 20

What is happen in Proliferating or organizing stage of DAD?

Answer 20

Type II pneumocyte hyperplasia and granulation tissue. This can eventually resolve.

Question 21

What is happen in Late fibrotic stage?

Answer 21

If granulation tissue doesn’t resolve fibrosis of alveolar septa occurs and lung compliance decreases further.

Question 22

The DAD results to what?

Answer 22

Ventilation/Perfusion mismatches

Question 23

High oxygen tension is needed of what?

Answer 23

Treat hypoxia resulting from DAD, and oxygen toxicity from this therapy exacerbates DAD.

Question 24

Explains the clinical findings of DAD

Answer 24

Severe dyspnoea and tachypnoea, follwed by respiratory failure, hypoxemia and cyanosis. Loss pf functional surfactant results in lunggs becoming stoff, requiring intubation and high ventilatory pressure.

Question 25

Explain radiology of DAD

Answer 25

Diffuse bilateral infiltrates

Question 26

Explain clinical course of DAD

Answer 26

Moderately high mortality rate due to sepsis, multiorgan failure or severe lung injury. Most survivors recover pulmonary function but a minority develop chronic lung disease due to fibrosis