Pathology of Restrictive Lung Disease - UIP

Question 1

What is UIP

Answer 1

Usual interstitial pneumonitis

Question 2

In which diseases can UIP be seen

Answer 2

Connective tissue diseases
Drug reaction
Post infection
Industrial exposure
Others

Question 3

In what main types of connective tissue diseases can UIP be seen

Answer 3

Scleroderma and Rheumatoid disease

Question 4

What type of industrial exposure can cause UIP

Answer 4

Asbestos

Question 5

Why can UIP be called IPF or CFA, What do they stand for

Answer 5

Most cases of UIP are cryptogenic or idiopathic
Iiopathic pulmonary fibrosis (IPF)
Cryptogenic fibrosing alveolitis (CFA)

Question 6

What will the histopathology of UIP show

Answer 6

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

Question 7

Give 6 common features of UIP

Answer 7

Occurs in the elderly (over 50)
Males affected more than females
Progressive disease – many die within 5 years of presentation
CXR shows Basal/Posterior, Diffuse infiltrates, Cysts, ‘Ground Glass’
Restrictive PFT & Reduced Gas Transfer
Poor Prognosis

Question 8

What are the symptoms of UIP

Answer 8

Dyspnoea
Cough
Basal Crackles
Cyanosis
Clubbing

Question 9

Which agents have been effective in UIP and which are ineffective

Answer 9

Effective - anti-angiogenic agents

Ineffective - Steriods

Question 10

In what two forms can the air in the airways move and what is it dependent on

Answer 10

Laminar or Turbulent

Dependent on the pressure difference

Question 11

How is gas exchanged beyond the terminal bronchiole

Answer 11

Diffusion

Question 12

What does the affinity of Hb for oxygen allow

Answer 12

The blood which leaves the capillary bed is 98% saturated for FIO2 of only 0.21

Question 13

What does the soulbility of CO2 allow

Answer 13

CO2 can rapidly equilibrate between the blood and air

Question 14

What are normal PaO2 levels

Answer 14

10.5 - 13.5 kPa

Question 15

What are normal PaCO2 levels

Answer 15

4.8-6.0 kPa

Question 16

What are PaO2 levels in type I respiratory failure

Answer 16

PaO2 <8 kPa (PaCO2 normal or low)

Question 17

What are PaCO2 levels in type I respiratory failure

Answer 17

PaCO2 >6.5 kPa (PaO2 usually low)

Question 18

What are the 4 abnormal states associated with hypoxaemia

Answer 18

Alveolar Hypoventilation
Shunt
Ventilation / Perfusion imbalance - V/Q
Diffusion impairment

Question 19

What is FIO2

Answer 19

The Fraction of Inspired air which is Oxygen

Question 20

What is alveolar hypoventilation

Answer 20

The amount of air moved in and out of the lungs

Question 21

What happens in alveolar hypoventilation

Answer 21

PACO2 increases so PaCO2 increases. The increase in PACO2 causes a decrease in PAO2 causing PaO2 to fall

Question 22

How is a fall in PaO2 due to hypoventilation corrected

Answer 22

By raising FIO2

Question 23

What is the normal V/Q level

Answer 23

We normally breath 4L/min and CO is 5L/min so normal V/Q is 4/5 or 0.8

Question 24

What is the commonest cause of hypoxaemia encountered clinically

Answer 24

Low V/Q

Question 25

How can low V/Q in some alveoli arise

Answer 25

Due to local alveolar hypoventilation due to some focal disease

Question 26

What does hypoxaemia due to low V/Q respond to

Answer 26

Small increases in FIO2

Question 27

What is diffusion impairment

Answer 27

When it takes longer for blood and alveolar air to equilibrate, particularly for oxygen.

Question 28

What is the gas flow through a membrane dependent on

Answer 28

The thickness and surface area of the membrane and the gas pressure across it.

Question 29

Why can CO2 diffuse 20 times faster than O2

Answer 29

Due to its greater solubility

Question 30

Do diseases which impair gas diffusion change CO2 levels

Answer 30

Normally no

Question 31

What does diffusion impairment mean

Answer 31

That it takes longer for blood and alveolar air to equilibrate, particularly for oxygen.

Question 32

How long does equilibration normally take

Answer 32

0.25 seconds

Question 33

What is the normal capillary transit time

Answer 33

0.75 seconds

Question 34

How long can equilibration take in disease

Answer 34

May take close to 0.75 seconds so PaO2 is maintained at rest however there can be serious falls in PaO2 on exercise as RBC are spending less time in the capillary bed

Question 35

How can hypoxaemia be corrected in diffusion impairment

Answer 35

Increasing FIO2 | This increases PAO2, thus increasing rate of diffusion

Question 36

What is a shunt

Answer 36

When blood passes from the right side to the left side of the heart without contacting ventilated alveoli

Question 37

What is a normal shunt size

Answer 37

2-4%

Question 38

What can cause pathological shunts

Answer 38

AV malformations Congenital heart disease Pulmonary disease

Question 39

How will a large shunt respond to increases in FIO2

Answer 39

Poorly | The blood leaving the normal lung is already 98% saturated