Chapter 13: Atelectasis and ARDS

Question 1

What is the major function of the lung?

Answer 1

Replenish oxygen and remove carbon dioxide from blood

Question 2

Name the structure as you go into the lung (bronchioles, respiratory bronchioles, alveolar ducts, trachea, terminal bronchioles, alveolar sacs, alveoli, bronchi)

Answer 2

Trachea - bronchi (forming lobi) - bronchioles - terminal bronchioles - respiratory bronchioles - alveolar ducts - alveolar sacs - alveoli

Question 3

Of what components do the alveolar walls/septa consist (from blood to air)?

Answer 3

• The capillary endothelium and basement membrane.
• The pulmonary interstitium, composed of fine elastic fibers, small bundles of collagen, a few fibroblast-like cells, smooth muscle cells, mast cells, and rare mono-nuclear cells.
• Alveolar epithelium, consisting of a continuous layer of two principal cell types: flattened, plate-like type I pneumocytes covering 95% of the alveolar surface; and rounded type II pneumocytes. The latter synthesize pulmonary surfactant and are the main cell type involved in repair of alveolar epithelium after damage to type I pneumocytes.

Question 4

How can lung diseases broadly be divided into?

Answer 4

Those affecting the

1. airways
2. interstitium
3. pulmonary vascular system

Question 5

What is a synonym for collapse?

Answer 5

Atelectasis

Question 6

What is atelectasis

Answer 6

Loss of lung volume caused by inadequate expansion fo air spaces (collapse)

Question 7

Atelectasis results in shunting of inadequately oxygenated blood from pulmonary arteries into veins, thus giving rise to a … imbalance and …

Answer 7

ventilation-perfusion, hypoxia

Question 8

On the basis of the underlying mechanism and the distribution of alveolar collapse, atelectasis is classified into three forms. What are they?

Answer 8

• Resorption atelectasis (occurs when an obstruction prevents air from reaching distal airways)
• Compression atelectasis (usually associated with accumulation of fluid, blood, or air within the pleural cavity)
• Contraction atelectasis (occurs when local or diffuse fibrosis affecting the lung or the pleura hamper lung expansion)

Question 9

What is Acute Respiratory Distress Syndrome (ARDS)?

Answer 9

respiratory failure occurring within 1 week of a known clinical insult with bilateral opacities on chest imaging, not fully explained by effusions, atelectasis, cardiac failure, or fluid overload

Question 10

What is typical of all ARDS?

Answer 10

extensive bilateral injury to alveoli

Question 11

What is severe ARDS characterized by?

Answer 11

Rapid onset of life- threatening respiratory insufficiency, cyanosis, and severe arterial hypoxemia that is refractory to oxygen therapy. Histology: diffuse alveolar damage (DAD)

Question 12

What is seen on cellular level in ARDS?

Answer 12

The integrity of the alveolar-capillary membrane is compromised by endothelial and epithelial injury (due to neutrophils!!!)

Question 13

Do most patients survive? How long does it take to recover

Answer 13

Yes, 6-12 months, but the rest develop diffuse interstitial fibrosis leading to chronic respiratory insufficiency