L19 Vascular disorders of the lung

Question 1

What are the 2x routes by which lungs are supplied with blood?

Answer 1

Pulmonary artery- Pulmonary veins –> blood for O2 transfer @ alveoli, and supplies distal bronchioles

Bronchial artery from aorta –> blood supply to parenchyma, CT, bronchi

Question 2

Contrast the flow and pressure of the pulmonary and bronchial arterial systems

Answer 2

Pulmonary high flow, Low pressure

Bronchial, low flow, high pressure

Question 3

Describe the dual drainage of the lungs

Answer 3

Pulmonary veins drain capillary beds supplied by pulmonary artery to L heart

Azygous veins drain capillary beds supplied by bronchial artery to R heart

Question 4

Describe the 2x sets of lymphatic drainage of the lungs

Answer 4

Superficial- drains CT of visceral pleura, interlobular septa

Deep- CT of distal bronchioles

*there are also anastomoses b/w both at interlobular septa

Question 5

What are the blood-air barrier components from lumen outwards

Answer 5

Alveolar fluid + surfactant > epithelial cells (mostly Type1) > basement membrane > alveolar interstitial > monolayer capillary endothelial cells w/ basement membrane

Question 6

Which cell type can actively resorb Na

Answer 6

Type II pneumocytes (Club) that have Na-K-ATPase pumps

Question 7

According to Starling’s forces, some fluid will leave capillaries to enter alveoli, what prevents this fluid from flooding the alveoli?

Answer 7

• Limited by interstitial oncotic pressure (albumin)
• Type II pneumocutes passive Na channels
• Clara cells of distal bronchioles also extract via osmosis
• Rapid drainage b/c pressure becomes lower towards hilus of lungs

Question 8

What are the 2x main mechanisms responsible for pulmonary oedema?

Answer 8

Inc hydrostatic pressure @ capillaries

Inc permeability of blood-alveolar barrier

Question 9

Explain how INC hydrostatic pressure at the capillaries leads to pulmonary oedema

Answer 9

Inc hydrostatic pressure @ capillaries -> fluid leaks -> overloading of drainage system -> initial accumulation of oedema @ bronchovascular interstitium -> spillage into alveoli

oedma= low protein

Question 10

Explain mechanisms how inc permeability of blood-alveolar barrier can lead to pulmonary oedema

Answer 10

1. inflammation of lung parenchyma w/ inc vascular permeability, common in interstitial pneumonia
2. direct damage to endothelium (e.g. uraemia)
3. Direct damage to Type1 pneumocystis (e.g. ROS, NH3, H2S, smoke)
4. Hypoalbuminaemia is less common (hepatic Dz)

High protein oedema

Question 11

What special histo characteristic hints that pulmonary oedema might be due to increased permeability of the blood-alveolar barrier?

Answer 11

Hyaline membranes (intra alveolar fibrin strands)

Question 12

Grossly, how will oedematous lungs appear?

Answer 12

wet 
heavy 
rubbery 
don't collapse w/ thorax opening 
distension of septa

Question 13

Why might pulmonary congestion occur?

Answer 13

L sided heart failure (passive)

Prolonged recumbency (hypostatic congestion)

Lung lobe torsion

Question 14

What might chronic passive congestion lead to?

Answer 14

fibrosis of alveolar septa

Accumulation haemosiderin by alveolar macrophagieaojsdnf

Question 15

Under what circumstances would lungs experience active hyperaemia

Answer 15

Subacute lung injury & inflammation

Vasodilation
e.g. Red phase pneumonia

Question 16

Grossly, how does pulmonary haemorrhage appear and how might it be distinguished from congestion?

Answer 16

Congestion is diffuse, haemorrhage Moore likely to be multifocal and patchy (petechia- massive)

Question 17

What is a common cause of pulmonary haemorrhage in hoses

Answer 17

EIPH

Rupture alveolar capillaries due to exercise induced inc in transmural pressure (pressure b/w lumen of capillary and alveolar space)

Exericse= marked inc in pulmonary arterial & alveolar capillary pressure (e.g. 25->90mmHg)

Marked decrease in -ve pressure

Dorsocaudal diaphragmatic lobes

Question 18

How might the histology compare with acute vs. chronic EIPH

Answer 18

Acute= blood @ trachea/ bronchi/ in macros @ BAL/ epistaxis

Chronic= alveolar interstitial fibrosis, siderophages, bronchiolitis, peribronchiolar fibrosis

Question 19

Why is there an increased chance of a horse suffering EIPH again after a first episode

Answer 19

pulmonary fibrosis reduces compliance @ interface b/w normal and affected lung

small airway obstruction –> weird shear stress

Question 20

how can pulmonary obstruction lead to cor pulmonale and what is a likely consequence

Answer 20

thrombi suddenly obstruction over 60% pulmonary arterial flow –> cariogenic shock/ cor pumonarle

Question 21

Why might pulmonary infarction occur?

Answer 21

obstruction of small/ medium arterial branch (any bigger & can go into shock/ cor pulmonale) might cause infarction if O2 supply to that area is already shit
e.g. congestion, atelectasis, pneumonia, anaemia

Question 22

What might cause a thrombis to be thrown into a pulmonary artery?

Answer 22

vegetative endocarditis of a valve

parasitism

DIC

prologned recumbency –> clot in leg

jugular, hepatic, CaVC vein thrombo

Pulmonary vasculitis

Question 23

Why is septic thrombo/embolism even shitter to get if you’re a lung

Answer 23

will set up a new infection

septic pulmonary infarcts > multifocal pulmonary abscessation > multifocal suppurative pneumonia/ interstitial pneumonia

Question 24

How might a lung twist ? Which is usually the culprit?

Answer 24

If you’re a deep chested dog ?? Predisposed by neoplasia, pneumonia, atelectasis, effusion, pneumothorax bla bla etc

Gen the R middle b/c long and narrow or left cranial lobe

Question 25

What are some causes of pulmonary vasculitis

Answer 25

parasitism
viral e.g. FiP , Hendra, EHV1, Nipah, BVD

i.e. septicaemia/ septic thrombi

Question 26

What might cause pulmonary hypertension?

Answer 26

Pulmonary Dz increasing pulmarony arterial blood flow (tumour, interstitial fibrosis, pnueonona, atelecstasissi etc)

heart worm @ pulmonary branch

Cardiac anomalies w/ L-R shunting (PDA, ASD, VSD)

Question 27

What is brisket Dz

Answer 27

oedematous swelling of briksein in cattle w/ R congestive heart failure due to failure of cardioresp system to adjust to hypoxia of high altitudes

hypoxia > sustained vasoconstriction of pulmonary arterioles > pulmonary hypertension > cor pulmonlae +/- RSCHF