Pathology of Restrictive Lung Diseases

Question 1

What is the interstitial of the lung?

Answer 1

The connective tissue space around the airways and vessels and the space between the basement membranes of the alveolar walls - capillaries and pneumocytes pushed apart

Question 2

What can the alveolar wall be thickened by?

Answer 2

Interstitial infiltrate

Question 3

How is lung compliance affected?

Answer 3

Reduced (stiff lungs)

Question 4

How is FEV1 and FVC affected?

Answer 4

Both reduced

Question 5

How is the FV1/FVC ratio?

Answer 5

Normal ratio

Question 6

What do obstructive lung diseases do to residual volume?

Answer 6

Increase

Question 7

How does restrictive lung disease affect residual volume?

Answer 7

Reduces it

Question 8

How does restrictive lung disease affect expiratory reserve volume?

Answer 8

Reduces it

Question 9

How is gas transfer affected?

Answer 9

Reduced due to diffusion abnormality

Question 10

Why is gas transfer reduced in restrictive lung diseases?

Answer 10

The distance between alveoli and capillaries is increased as there is increases tissue in the interstitium

Question 11

What does a diffuse lung disease present as?

Answer 11

Abnormal CXR
Dyspnoea - exertion then rest
Type I respiratory failure
Heart failure

Question 12

Why do sufferers of restrictive lung disease experience type 1 respiratory failure?

Answer 12

It is much easier for carbon dioxide to diffuse across the thickened alveolar walls than it is for oxygen

Question 13

What is diffuse avleolar damage associated with?

Answer 13

Major trauma
Chemical injury / toxic inhalation
Circulatory shock
Drugs 
Infection
Auto(immune) disease
Radiation
idiopathic

Question 14

What is the evolution of DADs?

Answer 14

Oedema -> Hyaline membranes ->interstitial inflammation -> interstitial fibrosis

Question 15

What are the histological features of DADs?

Answer 15

Protein rich oedema
Fibrin
Hyaline membranes
Denuded basement membranes
Epithelial proliferation
Fibroblast proliferation
Scarring-interstitium and airspaces

Question 16

What is the acute response to parenchymal (interstitial) lung injury?

Answer 16

Diffuse alveolar damage (DAD)

Question 17

What is another response of parenchymal lung injury, which can also carry on from the acute response?

Answer 17

Chronic response which leads to fibrosis or end-stage honeycomb lung

Question 18

What are three conditions that arise from the chronic response?

Answer 18

Interstitial Pneumonitis (UIP)
Granulomatoud responses: sarcoidosis, hypersensitivity pneumoniitis

Question 19

What are sarcoidosis?

Answer 19

A multisystem granulomatous disorder of unknown aetiology

Question 20

Describe the histopathology of sarcoidosis

Answer 20

Epithelioid and giant cell granulomas

Necrosis/caseation unusual

Question 21

What are the different presentation of sarcoidosis?

Answer 21

1. Young adult - acute arthralgia, erythema nodosum, bilateral hilar lymphadenopathy
2. Incidental abnormal CXR - no symptoms
3. SOB, cough and abnormal CXR

Question 22

If patient experiences symptoms of sarcoidosis (i.e. presentation 1) when should they resolve?

Answer 22

After 2 years

Question 23

What treatment is given for sarcoidosis?

Answer 23

Costicosteroids (for SOB, cough)

Question 24

How is sarcoidosis diagnosed?

Answer 24

Clinical findings
Imaging finding
Serum Ca ++ and ACE
Biospy

Question 25

What are the antigens for hypersensitivity pneumonitis?

Answer 25

Thermophilic actinomycetes Bird / animal proteins Fungi (aspergillus spp.) Chemicals

Question 26

What is the acute presentation of hypersensitivity pneumonitis?

Answer 26

Fever, dry cough, myalgia Chills after Ag exposure Crackles, tachypnoea, wheeze Precipitating antibody

Question 27

What is the chronic presentation of hypersensitivity pneumonitis?

Answer 27

Insidious Malaise, SOB, cough Low grade illness Crackles and some wheeze

Question 28

What is the histopathology of hypersensitivity pneumonitis?

Answer 28

``` Immune complex mediated by combine Type II and Type IV hypersensitivity reaction Soft centriacinar epithelioid granuloma Interstitial pneumonitis Foamy histiocytes Bronchiolitis obliterans ```

Question 29

What is bronchiolitis obliterans in hypersensitivity pneumonitis?

Answer 29

Obstruction of the smallest airways of the lungs (bronchioles) due to inflammation

Question 30

What part of the lung is common for hypersensitivity pneumonitis?

Answer 30

Upper zone

Question 31

Where might UIP be seen?

Answer 31

``` Connective tissue disorders Drug reaction Post infection Industrial exposure: asbestos Most cryptogenic or idiopathic ```

Question 32

What is the histopathology of UIP?

Answer 32

Patchy interstitial chronic inflammation Type II pneumocyte hyperplasia Smooth muscle and vascular proliferation

Question 33

What are clinical signs of UIP?

Answer 33

``` Dyspnoea Cough Basal crackles Cyanosis Clubbing ```

Question 34

What are the investigations for UIP?

Answer 34

``` CXR PFT (shows restriction) Gas transfer (reduced) ```

Question 35

What are other patterns than can cause fibrosis or honey combing of the lung?

Answer 35

``` Asbestos Silicosis Smoking related fibrosis Cryptogenic organizing pneumonia (COP) Bronchiolitis obliterans organizing pneumonia (BOOP) ```

Question 36

What are the levels for Type I and Type II respiratory failure?

Answer 36

Type I - PaO2 < 8kPa (PCO2 normal) | Type II - PaCO2 > 6.5 kPa (PaO2 low)

Question 37

What are 4 abnormal states associated with hypoxaemia?

Answer 37

Shunt V/Q mismatch Diffusion impairment Alveolar hypoventilation

Question 38

How does alveolar hypoventilation lead to low PaO2?

Answer 38

Increase PACO2, and thus PaCO2 | Increase in PACO2 decrease PAO2, which causes PaO2 to fall

Question 39

How is a fall in PaO2 due to hypoventilation corrected?

Answer 39

Raising FlO2 (fraction of inspired air which is oxygen)

Question 40

What is the normal V/Q ratio?

Answer 40

Breath 4min/l, CO is 5l/min so normal V/Q = 0.8

Question 41

How does diffusion impairment affect equilibrium across alveoli?

Answer 41

Takes longer for blood and alveoli air to equilibrate, particularly for O2 - usually 0.25s, but may take 0.75s in disease