overview of respiratory pathologies Part 3: major restrictive lung diseases

Question 1

restrictive lung diseases

what are the 2 categories of restrictive lung diseases and give 1-2 examples for each

Answer 1

Acute:
- ARDS ( acute respiratory distress syndrome

Chronic ( interstitial ):
- idiopathic pulmonary fibrosis
- pneumoconiosis

Question 2

ARDS

what happens in Acute respiratory distress syndrome

Answer 2

acute inflammation of alveoli due to neutrophils, rapidly damaging cappillaries and epithelium

Question 3

what 2 things can cause the alveolar damage in ARDS

Answer 3

Direct causes:
- pneumonia/aspiration of gastric contents

indirect causes:
- sepsis/severe trauma causing lung injury

Question 4

outline 5 steps of the pathogenesis in ARDS

Answer 4

1. damaging stimulus to lung
2. this leads to damage to cells lining the alveoli and damage to the alveolar capillary endothelium, leading to increased permeablility
3. this leads to interstitial oedema and high protein exudation into the alveoli, which impairs oxygen gas exchange
4. this can lead to either a good outcome with regenerate of type II alveolar lining cells, OR a bad outcome with inflammation of the interstitium.
5. this leads to organisation of scar tissue, leading to interstitial fibrosis, which then becomes marked intersititial fibrosis (honeycomb lung), and can then cause death

Question 5

what leads to the inflammation in ARDS

Answer 5

there is an imbalance of pro and anti-inflammatory mediators, leading to uncontrolled inflammation

Question 6

why is there acute onset of dyspnea and hypoxemia in ARDS

Answer 6

due to cascular leakiness and loss of surfactant affecting gaseous exchange

Question 7

idiopathic pulmonary fibrosis

what is persistent inflammation of alveolar walls and spaces known as in IPF?

Answer 7

alveolitis

Question 8

in IPF, what does lung injury induce, causing excessing and persistent deposition of collagen and extracellular matrix?

Answer 8

injury induces proliferation of fibroblasts, which then transform to myofibroblasts

Question 9

IBF morphology

what are myofibroblasts, what do they do in IPF and what does this lead to

Answer 9

• specialised contractile cells with increased capacity for collagen synthesis
• myofibroblasts in IBF deposit collagen and ECM excessively for an extended time
• leads to patchy interstitial fibrosis that worsens over time

Question 10

what forms in the lungs in IPF, how does this affect the lungs morphology and what does this lead to

Answer 10

• fibroblastic foci
• this makes the lungs more collagenous and less cellular
• this causes the collapse of alveolar walls and formation of cystic spaces (honeycomb fibrosis)

Question 11

pneumoconiosis

what is pneumoconiosis

Answer 11

group of fibrosing diseases resulting from exposure (usually occupational) to toxic inhaled particulates

Question 12

what are the 3 types of pneumoconiosis and what particulates and inhaled in each

Answer 12

asbestosis:
- particulate: asbestos

Silicosis:
- Particulate: silica

coal workers pneumoconiosis:
- particulate: coal dust

Question 13

what stimulates the immune response in pneumoconiosis

Answer 13

by particles and macrophages travelling in lymphatics

Question 14

pneumoconiosis: types

why do asbestos works that smoke have a higher chance of lung cancer

Answer 14

• this is because this combination often leads to a lung carcinoma due to adsorption of carcinogens onto fibres trapped deep in the lung

Question 15

what do lesions consist of in pneumoconiosis?

Answer 15

lesions consist of pigmented/pale nodules of particle laden macrophages and dense collagen