Pulmonary circulation

PULMONARY CIRCULATION

1. DR NILESH KATE
MBBS,MD
ASSOCIATE PROF
ESIC MEDICAL COLLEGE, GULBARGA.
DEPT. OF PHYSIOLOGY
PULMONARY
CIRCULATION

2. OBJECTIVES.
FUNCTIONAL ANATOMY
CHARACTERISTIC FEATURES
FUNCTIONS
REGULATION OF PULMONARY BLOOD FLOW.

3. FUNCTIONAL ANATOMY
Lungs have 3 circulation.
Pulmonary
circulation
Bronchial circulation
Lymphatic
circulation.
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4. PULMONARY CIRCULATION
Pulmonary trunk
Right & left pulm
artery
Right & left lungs
Capillaries lining of
alveoli
Get oxygenated &
return back via pul
veins to left atrium.
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5. BRONCHIAL CIRCULATION
Descending thoracic aorta
give right & left bronchial
arteries
Supply oxygenated blood to
lungs (connective tissue,
septa & bronchi) & after joins
pulm veins without (Bypass)
oxygenation.
So forms Physiological
shunt.
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6. OTHER EXAMPLE OF
PHYSIOLOGICAL SHUNT
Drainage of Coronary vessel in to left side of
heart.
Effects of shunts –
Reduce oxygenation of arterial blood slightly.
Increase left ventricular output by 1-2% than right.
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7. LYMPHATIC CIRCULATION.
Present in walls of
terminal bronchioles
& supportive tissues
of lung.
Removes particulate
matter, plasma
proteins –thus
prevents pulmonary
oedema
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8. LYMPHATIC CIRCULATION.
Drainage pathway
Deep lymphatic
Pulmonary nodes
Bronchopulmonary
nodes
Tracheobronchial
nodes
Bronchomediastinal
trunk.
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9. PULMONARY CIRCULATION
CHARACTERISTIC FEATURES.
Pulmonary circulation is low pressure, low
resistance & high capacitance system.
Thickness of Right ventricle and pulmonary
artery 1/3
rd
of left ventricle & aorta
Pulmonary capillaries are larger in diameter
than systemic capillaries.
Each alveolus is enclosed in basket of
capillaries.
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10. PRESSURES IN PULMONARY
SYSTEM.
Right ventricular pressure.
Pulmonary artery pressure.
Left atrial pressure.
Pulmonary capillary pressure.
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11. RIGHT VENTRICULAR
PRESSURE.
During each cardiac cycle,
During Systole–reaches peak 25 mm
Hg.(120 mm Hg in Left ventricle)
During Diastole–0-1 mm Hg (5 mm Hg in
left ventricle)
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12. PULMONARY ARTERY
PRESSURE.
Systolic pressure25 mm Hg (120 mm Hg in
Aorta)
Diastolic pressure8 mm Hg (8 mm Hg in
Aorta)
Mean arterial pressure15 mm Hg (100 mm
Hg in Aorta)
Pulse pressure17 mm Hg (40 mm Hg in
Aorta)
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13. LEFT ATRIAL PRESSURE.
Major pulmonary veins pressure avg5 mm
Hg
So Pressure gradientin pulmonary system
Mean pulmonary artery pressure –mean
pulmonary vein pressure
15-5 = 10 mm Hg.
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14. PULMONARY CAPILLARY
PRESSURE.
10 mm Hg.
Colloidal osmotic pressure is 25 mm Hg
So net suction force of 15 mm Hg draw fluid
from pulmonary interstitial fluid into
pulmonary capillary
So keeps Alveoli dry
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15. SIGNIFICANCE OF LOW PULMONARY
CAPILLARY PRESSURE
So if pulmonary capillary pressure rises above
25 mm Hg
Fluid escapes into interstitial spaces
Lead to pulmonary oedema
Conditions raising this pressue
Exercise at high altitude
Left heart failure
Mitral stenosis
Pulmonary fibrosis.
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16. PULMONARY WEDGE
PRESSURE
Estimate left atrial
pressure.
Measured by passing a
catheter through right
ventricle, pulmonary artery
up to smallest branch of
pulmonary artery.
Used to study left atrial
pressure in patients of CCF
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17. PULMONARY BLOOD VOLUME
Pulmonary vessels contains –600 ml; its
capacitance vary from 200-900 ml
Pulmonary blood volume decreases during
standing & during haemorrhageto
compensate , so acts as Reservoir.
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18. PULMONARY BLOOD FLOW
Pulmonary blood flow
nearly equal to cardiac
output.
Blood flow through lung
depend on –
Relationship between
pressures of Pulmonary
artery, pulmonary vein &
alveolar artery.
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19. EFFECT OF GRAVITY ON REGIONAL
PULMONARY BLOOD FLOW.
In supine position
mean arterial pressure
is same all over lung
so all regions equally
perfused.
In erect position
gravity affects due to
hydrostatic pressure
effect.
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20. EFFECT OF GRAVITY ON REGIONAL
PULMONARY BLOOD FLOW.
Zero reference plane is
at level of right atrium.
So pulmonary arterial
pressure
In middle of lung –is 15
mm Hg
At apex –4 mm Hg
At the base 26 mm Hg.
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21. PERFUSION ZONES OF LUNG
Depending on
relationship between
alveolar pressure
(PA), Pulmonary
arterial pressure(Pa)
& Pulmonary venous
pressure(Pv) 3 zones
Zone 1
Zone 2
Zone 3
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22. PERFUSION ZONES OF LUNG
Zone 1-area of zero
flow. (Pa<Pv)
Does not exist in normal
lung.
In hypovolaemicshock,
pulmonary embolism.
Zone 2–Intermittent
blood flow.(Pa>PA>Pv)
Occurs during systole.
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23. PERFUSION ZONES OF LUNG
Blood flow is
determined by arterial-
alveolar pressure
gradient not arterio-
venous gradient. so
called Waterfall effect.
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24. PERFUSION ZONES OF LUNG
Zone 3
Continuous high blood
flow. (Pa>Pv>PA)
Generally occurs near
bottom of the lung.
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25. EFFECT OF GRAVITY ON
ALVEOLAR VENTILATION
In Supine Position–alveolar ventilation evenly
distributed
In Upright Position–
Alveolar pressure is zero throughout lung
Intrapleural pressure –at apex -10 mmHg & at base -2
mm Hg.
So transpulmonary pressure -10 & -2 at apex & base
respectively.
So linear reduction in regional alveolar ventilation from
base to apex.
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26. CLINICAL SIGNIFICANCE
So arterial
oxygenation in
unilateral lung
diseases is improved
by keeping good lung
in Dependent
Position.
Opposite is done in
INFANT.
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27. ALVEOLAR VENTILATION :
PERFUSION RATIO
Ratio of alveolar
ventilation per minute
to quantity of blood
flow to alveoli per
min.
VA/Q = 4.2/5 = 0.84-
0.9
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28. EFFECT OF GRAVITY
Linear Reductionof blood flow and
alveolar ventilation from base to
apex.
But gravity affects perfusion more
than ventilation.
So as we go up from middle VA/Q
goes on increasing , about 3 at apex.
At the base it is over perfused than
over ventilated so at the base is 0.6
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29. CAUSES OF ALTERATION.
Causes of altered
alveolar ventilation
Bronchial asthma
Emphysema
Pulmonary fibrosis
Pneumothorax
Congestive heart failure
Causes of altered
pulmonary perfusion.
Anatomical shunts
Pulmonary embolism
Decrease in pulmonary
vascular bed in
emphysema
Increase pulmonary
resistance in pulmonary
fibrosis, Pneumothorax,
CHF
Thursday, December 5, 2019

30. EFFECTS OF ALTERATION IN
VA/Q RATIO.
Normal VA/Q ratio –both normal alveolar
pO2 = 104 mmHg, pCO2 =40 mmHg.
Increased VA/Q ratio. –alveolar dead space
air, VA/Q = infinity, pO2 = 149 mmHg, pCO2
= 0 mmHg.
Decreased VA/Q ratio, pO2 = 40 mmHg,
pCO2 = 45 mmHg.
Thursday, December 5, 2019

31. EFFECT OF EXERCISE ON REGIONAL
PULMONARY BLOOD FLOW
During exercise blood flow
increases in all regions of
blood.
Near base increased by 2-3
time
Near apex increased by 8
times.
It occurs due to
Recruitment of capillaries.
Distension of capillaries.
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32. PULMONARY CAPILLARY
DYNAMICS
Pulmonary transit time –mean transit time
in pulmonary circulation from pulmonary
valves to left atrium –4 sec.
Capillary transit time for RBC is 0.8 sec at
rest and 0.3 sec during exercise.
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33. MEAN FILTRATION PRESSURE AT
PULMONARY CAPILLARY = 1 mm Hg.
Starling’s forces at capillary membrane
are
Outward forces (29 mm Hg)
Interstitial oncotic pressure –14 mmHg
Interstitial hydrostatic pressure --8 mm Hg
Capillary Hydrostatic pressure 7 mm Hg
Inward forces (28 mm Hg)
Plasma oncotic pressure 28 mm Hg.
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35. PULMONARY OEDEMA
Occur due to increase capillary filtration
from pulmonary capillary.
Conditions–
Increase capillary hydrostatic pressure from 7 mm
Hg to 28 mm Hg (safety factor of 21 mm Hg)
Capillary permeability increase –due to infection,
irritant gases.
Acute left heart failure –increase in capillary
pressure to 50 mm Hg.
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36. FUNCTIONS
Respiratory gas exchange
Other functions
Reservoir for left ventricle
Filter for removal of emboli & other particles from
blood.
Removal of fluid from alveoli.
Role in absorption of drugs.
Synthesis of Angiotensinconverting enzyme.
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37. REGULATION OF PULMONARY
BLOOD FLOW.
Neural control.
Efferent sympathetic vasoconstrictor
nerves
Innervates pulmonary blood vessels.
Participate in vasomotor reflexes.
Baroreceptorstimulation–causes reflex
dilatation of pulmonary vessels
Chemoreceptor stimulation–causes pulmonary
vasoconstriction.
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38. Afferent control through vagus
is mediated through receptors.
Pulmonary
baroreceptors
pulmonary volume
receptors
J receptors.
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39. CHEMICAL CONTROL
Local Hypoxia–causes
change in blood flow by
vasoconstriction.
Hypercapnia &
acidosis–causes
vasoconstriction.(Vasod
ilatation in systemic
circulation)
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40. CHEMICAL CONTROL
Chronic Hypoxia
Occurs in high altitude dwellers associated with
pulmonary hypertension followed by right
ventricular hypertrophy, right heart heartfailure &
pulmonary oedema.
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41. THANK YOU