pulmonary circulation

Question 1

Describe the pulmonary circulation

Answer 1

pul artery = low oxygen blood
pul vein = high ox blood
function: perfusion of resp airways for GE

Question 2

Comparison of the systemic circulation with the pulmonary circulation

Answer 2

different wall thickness: lumen ratio
pul circ - thinner walls because going to a smaller distance
in heart LV main compartment
RV ‘additional’ - less mechanically strong force and structure - shorter distance

Question 3

circuit pressures in systemic and pul circulation `

Answer 3

LV give on/off pressure, systole/diastole
aorta - vascular compliance so make flow more pulsatile
blood goes from low to high pressure
pulmonary circuit similar process - under much lower pressure

Question 4

cardiac parameters in systemic and pulmonary systems

Answer 4

pul has 10% of blood vol
blood is mainly in systemic/pul veins
pul has 15% pressure
pul has 10% of the pressure gradient - impacts the velocity
pul is a low resistance circuit - more resistance = faster, needs time to load

Question 5

3 functions of the pulmonary circulation

Answer 5

GE
metabolism of vasoactive substances
filtration of blood

Question 6

GE

Answer 6

deliver O2, take CO2 
CO2 move quick - v diffusible 
anaesthetic moves from lungs to neurological system 
NO inert so travels in and out of lungs 
pulmonary transit time .75s

Question 7

metabolism of vasoactive substances

Answer 7

endothelium that expresses ACE - convert ANG1 - ANG2 - vasoconstrictor
break down bradykinin (vasodilator)
only expressed at end of lungs or in the kidney

Question 8

Filtration of the blood

Answer 8

filters things that get ‘caught’ before they reach the systemic arteries
eg venous thrombosis from stasis, ruptured fatty plaques, air bubbles
small embolus - eliminated in pul microcirc
large embolus - trapped in pul microcirc - local perfusion obstructed - can stop flow to entire lung - affects pressure and GE - better than in systemic `

Question 9

embolus

Answer 9

mass in circulation capable of causing an obstruction `

Question 10

embolism

Answer 10

event characterised by the obstruction of a major artery

Question 11

in theory what should happen if CO (Q) is increased

Answer 11

increase MAP
therefore increase leakage
= pul oedema
reduced lung function

Question 12

what actually happens when Q is increased in pul circ

Answer 12

pul artery distension - prevent increases in MAP
also the increase in pressure increases perfusion of the apex of the lung - increased throughput of the lung
both mean Q is increased with little increase in MAP
minimal fluid leakage
no onset of pul oedema
no detriment to pul func

Question 13

pulmonary response to hypoxaemia

Answer 13

closure of O2 sensitive K+ channel 
reduced KJ efflux 
increased mem potential 
membrane depol = open V gated Ca channel 
vascular sm constriction

Question 14

effect of breathing hypoxic air

Answer 14

global vasoconstriction 
RV work hard against resistance 
get stronger 
concentric hypertrophy 
septum change 
change in EDV on L 
affect in SV

Question 15

beneficial effect of pul vasoconstriction with hypoxia

Answer 15

in foetus
perfusion matches inadequate ventilation
blood follows path of least resistance
increased flow through shunt (pul circuit is higher pressure)
first breath increases alveola PO2 - dilate the vessels

Question 16

when is vasoconstriction as a result of hypoxia detrimental

Answer 16

COPD 
reduced ventilation 
increased resistance in pul circuit 
= pul hypertension 
RV hypertrophy
congestive heart failure

Question 17

Why is there a fluid balance in the lungs

Answer 17

vessels aren’t water tight

factors effect movement and move the water into the extracellular space

Question 18

important components in the Starling eqn

Answer 18

hydrostatic pressure in the interstitium Pi
hydrostatic pressure in the capillary Pc
oncotic pressure in the interstitium (pi)i
oncotic pressure in the capillary (pi)c

Question 19

describe the fluid balance in the lungs

Answer 19

plasma hydrostatic - highest when first get to capillary, forces fluid out
interstitial hydrostatic - tiny sucking force (ie negligible move out)
plasma oncotic - big sucking force into the vessel
interstitial oncotic - force out of the vessel
net movement out
small leakage
increase in interstitial hydrostatic pressure
pulmonary circulation can manage - uses -ve pressure to mop up the fluid
easier for the excess fluid to drain into the lymph and then drain into the capillaries

Question 20

what happens if there is excess fluid

Answer 20

fluid exceeds ability of lymph to drain it

pulmonary oedema

Question 21

effect of mitral valve stenosis on fluid balance

Answer 21

pressure build up from L of heart through pul circulation 
increased plasma hydrostatic pressure 
more fluid forced into the interstitium 
max lymph clearance rate exceeded 
pul oedema

Question 22

effect of liver failure on fluid balance

Answer 22

plasma oncotic reduced - less plasma proteins made
less fluid drawn into the capillary 
fluid accumulates in the interstitium 
lymph clearance exceeded 
oedema

Question 23

effect of metastatic breast cancer on fluid balance

Answer 23

cancer spresd to lympoh nodes
tumours obstruct lymphatic drainage
lymph clearance compromised
oedema

Question 24

effect of increase in systemic pressure on fluid balance

Answer 24

no effect
systemic circulation doesn’t affect pul circ
unless shared cause like hypovolaemia

Question 25

the concept of shunting

Answer 25

circumstances associated with the bypassing of the resp exchange surface

Question 26

adult example of shunting

Answer 26

bronchial circulation
blood goes through the L side of the heart and the aorta to keep the tissue alive - some drains into the pul vein and reenters the left heart

Question 27

foetal shunting

Answer 27

lungs not ventilated - so the bv are vasoconstricted
don’t want to pump blood into lungs = damage heart because of the high resistance
so shunt between atria - foreman ovale - close with 1st breath
ductus arteriosus - blood from pul artery straight to aortic arch

Question 28

complications if foetal shunts don’t close

Answer 28

congenital defect
atrial septal defect - deox and ox blood mix
open a little - stop the filtration function of the pul circulation
can have elective surgical repair
initial L side higher pressure = blood pushed through foreman ovale to R side = increased pressure on the R side
R side becomes stronger - blood pushed into L - less O2 in the systemic circ as mixed with deox blood

Question 29

shuntings affect on blood returm

Answer 29

more blood returns to the L of the heart
because of bronchial shunt
blood misses the pul circ ie the R side of the heart