L19 Vascular disorders of the lung Flashcards
What are the 2x routes by which lungs are supplied with blood?
Pulmonary artery- Pulmonary veins –> blood for O2 transfer @ alveoli, and supplies distal bronchioles
Bronchial artery from aorta –> blood supply to parenchyma, CT, bronchi
Contrast the flow and pressure of the pulmonary and bronchial arterial systems
Pulmonary high flow, Low pressure
Bronchial, low flow, high pressure
Describe the dual drainage of the lungs
Pulmonary veins drain capillary beds supplied by pulmonary artery to L heart
Azygous veins drain capillary beds supplied by bronchial artery to R heart
Describe the 2x sets of lymphatic drainage of the lungs
Superficial- drains CT of visceral pleura, interlobular septa
Deep- CT of distal bronchioles
*there are also anastomoses b/w both at interlobular septa
What are the blood-air barrier components from lumen outwards
Alveolar fluid + surfactant > epithelial cells (mostly Type1) > basement membrane > alveolar interstitial > monolayer capillary endothelial cells w/ basement membrane
Which cell type can actively resorb Na
Type II pneumocytes (Club) that have Na-K-ATPase pumps
According to Starling’s forces, some fluid will leave capillaries to enter alveoli, what prevents this fluid from flooding the alveoli?
- 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
What are the 2x main mechanisms responsible for pulmonary oedema?
Inc hydrostatic pressure @ capillaries
Inc permeability of blood-alveolar barrier
Explain how INC hydrostatic pressure at the capillaries leads to pulmonary oedema
Inc hydrostatic pressure @ capillaries -> fluid leaks -> overloading of drainage system -> initial accumulation of oedema @ bronchovascular interstitium -> spillage into alveoli
oedma= low protein
Explain mechanisms how inc permeability of blood-alveolar barrier can lead to pulmonary oedema
- inflammation of lung parenchyma w/ inc vascular permeability, common in interstitial pneumonia
- direct damage to endothelium (e.g. uraemia)
- Direct damage to Type1 pneumocystis (e.g. ROS, NH3, H2S, smoke)
- Hypoalbuminaemia is less common (hepatic Dz)
High protein oedema
What special histo characteristic hints that pulmonary oedema might be due to increased permeability of the blood-alveolar barrier?
Hyaline membranes (intra alveolar fibrin strands)
Grossly, how will oedematous lungs appear?
wet heavy rubbery don't collapse w/ thorax opening distension of septa
Why might pulmonary congestion occur?
L sided heart failure (passive)
Prolonged recumbency (hypostatic congestion)
Lung lobe torsion
What might chronic passive congestion lead to?
fibrosis of alveolar septa
Accumulation haemosiderin by alveolar macrophagieaojsdnf
Under what circumstances would lungs experience active hyperaemia
Subacute lung injury & inflammation
Vasodilation
e.g. Red phase pneumonia
Grossly, how does pulmonary haemorrhage appear and how might it be distinguished from congestion?
Congestion is diffuse, haemorrhage Moore likely to be multifocal and patchy (petechia- massive)
What is a common cause of pulmonary haemorrhage in hoses
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
How might the histology compare with acute vs. chronic EIPH
Acute= blood @ trachea/ bronchi/ in macros @ BAL/ epistaxis
Chronic= alveolar interstitial fibrosis, siderophages, bronchiolitis, peribronchiolar fibrosis
Why is there an increased chance of a horse suffering EIPH again after a first episode
pulmonary fibrosis reduces compliance @ interface b/w normal and affected lung
small airway obstruction –> weird shear stress
how can pulmonary obstruction lead to cor pulmonale and what is a likely consequence
thrombi suddenly obstruction over 60% pulmonary arterial flow –> cariogenic shock/ cor pumonarle
Why might pulmonary infarction occur?
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
What might cause a thrombis to be thrown into a pulmonary artery?
vegetative endocarditis of a valve
parasitism
DIC
prologned recumbency –> clot in leg
jugular, hepatic, CaVC vein thrombo
Pulmonary vasculitis
Why is septic thrombo/embolism even shitter to get if you’re a lung
will set up a new infection
septic pulmonary infarcts > multifocal pulmonary abscessation > multifocal suppurative pneumonia/ interstitial pneumonia
How might a lung twist ? Which is usually the culprit?
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
What are some causes of pulmonary vasculitis
parasitism
viral e.g. FiP , Hendra, EHV1, Nipah, BVD
i.e. septicaemia/ septic thrombi
What might cause pulmonary hypertension?
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)
What is brisket Dz
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
