pulmonarycirculation-1711160416power point presentationfor thursday presentation16.ppt

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1. REGULATION OF
PULMONARY CIRCULATION
BY- DR VIDYA PANDA
PG 1
ST
YEAR

2. P
ulmonary circulation - Features
P
ulmonary circulation - Features
1) Lung is the only organ which
receives the entire cardiac output
(RV) so accommodates a large
amount of blood.
2) It is a low pressure and low
resistance system as pulmonary
vessels are highly distensible.
3) The pulmonary artery extends only
5 centimeters beyond the apex of
the right ventricle and then divides
into right and left main branches that
supply blood to the two respective
lungs.

3. Tw
o sources of blood supply to lungs
Tw
o sources of blood supply to lungs
Tw
o sets of Blood vessels
A) Pulmonary artery of pulmonary circulation having
deoxygenated blood and function is gas exchange
B) Bronchial arteries arising from aorta of systemic
circulation having oxygenated blood to supply nutrition to
respiratory tree up to terminal bronchiole.
Physiologic shunt – Due to broncho - pulmonary
anastomosis it is the bronchial vessel blood which is not
oxygenated in alveolar capillaries and enters the pulmonary
vein directly and accounts for 1-2 % of shunted blood in
systemic circulation.
•This is also the reason that RV Output is little less than LV
Output.

4. P
ressures in the pulmonary system
P
ressures in the pulmonary system
RV
Pulmonary Artery
Pulmonary Capillary Pressure.
Left Atrial and Pulmonary Venous Pressures.

5. P
ulmonary wedge pressure
P
ulmonary wedge pressure
It is usually not possible to measure a human being’s left atrial
pressure using a direct measuring device because it is difficult to pass
a catheter through the heart chambers into the left atrium.
However, the left atrial pressure can often be estimated with
moderate accuracy by measuring the so-called pulmonary wedge
pressure.
Clinical importance of wedge pressureClinical importance of wedge pressure
•When the left atrial pressure rises to high values, the pulmonary
wedge pressure also rises.
•Therefore, wedge pressure measurements can be used to clinically
study changes in pulmonary capillary pressure and left atrial pressure
in patients with congestive heart failure.

7. H
ypoxia - VC substance
H
ypoxia - VC substance
•The low oxygen concentration causes some yet
undiscovered vasoconstrictor substance to be
released from the lung tissue;
•this substance promotes constriction of the small
arteries and arterioles.
•It has been suggested that this vasoconstrictor
might be secreted by the alveolar epithelial cells
when they become hypoxic.

8. I
mportance of Pulmonary
I
mportance of Pulmonary
v
asoconstriction by hypoxia
v
asoconstriction by hypoxia
•To distribute blood flow where it is most effective.
•That is, if some alveoli are poorly ventilated so that their
oxygen concentration becomes low, the local vessels
constrict.
•This causes the blood to flow through other areas of the
lungs that are better ventilated,
•thus providing an automatic control system for distributing
blood flow to the pulmonary areas in proportion to their
alveolar oxygen pressures.

10. Ex
ercise effect
Ex
ercise effect
•Exercise causes rise of CO and blood flow through
the lungs increases fourfold to sevenfold. This extra
flow is accommodated in the lungs in three ways:
•(1) by increasing the number of open capillaries,
sometimes as much as threefold;
•(2) by distending all the capillaries and increasing
the rate of flow through each capillary more than
twofold;

11. M
echanics of blood flow in the
t
hree blood flow zones of the lung

12. A
pex
A
pex
At the apical portion-
•Pulmonary capillary pressure is same as atmospheric
pressure in alveoli.
•So in normal conditions pulmonary arterial pressure is
just sufficient for blood flow in the capillaries.
•But if pulmonary arterial pressure is decreased or if
alveolar pressure is increased the capillaries collapse
•and thus no blood flow and hence apex is area of zero
blood flow

13. M
id portion of lung
M
id portion of lung
•Alveolar pressure is less than pulmonary artery systolic pressure but
more than its diastolic pressure.
•Hence blood flows in the alveolar pulmonary cap in systole and it is
prevented during diastole.
•So this part gets intermittent blood flow.
Lower portion of lungLower portion of lung
•Here the pulmonary arterial pressure is high and more than
alveolar pressure in both during systole and diastole.
•Thus there is a continuous blood flow in this part of the lung.

14. D
ynamics of fluid exchange
D
ynamics of fluid exchange
1)Low Pulmonary capillary pressure-
•The pulmonary capillary pressure is low, about 7 mm Hg, in
comparison with a considerably higher functional capillary
pressure in the peripheral tissues of about 17 mm Hg.
2)The interstitial fluid pressure in the lung is slightly more
negative than that in the peripheral subcutaneous tissue.
3)Leaky pulmonary capillaries – more COP of interstitial 3)Leaky pulmonary capillaries – more COP of interstitial
fluid- 14 mm Hgfluid- 14 mm Hg
4) Thin alveolar walls4) Thin alveolar walls

15. I
nterrelation between interstitial fluid and
I
nterrelation between interstitial fluid and
c
apillary pressures
c
apillary pressures

16. •Thus, the normal outward forces are slightly greater than the
inward forces, providing a mean filtration pressure which can be
calculated as follows

17. N
egative Interstitial pressure and
N
egative Interstitial pressure and
i
ts role in keeping alveoli dry
i
ts role in keeping alveoli dry
•Whenever extra fluid appears in the alveoli, it will simply
be sucked mechanically into the lung interstitium
through the small openings between the alveolar
epithelial cells.
•Then the excess fluid is either carried away through the
pulmonary lymphatics or absorbed into the pulmonary
capillaries.
•Thus, under normal conditions, the alveoli are kept “dry,”
except for a small amount of fluid that seeps from the
epithelium onto the lining surfaces of the alveoli to keep
them moist.

18. P
ulmonary edema
P
ulmonary edema
•Pulmonary edema occurs in the same way that edema occurs elsewhere in
the body.
•Any factor that causes the pulmonary interstitial fluid pressure to rise from
the negative range into the positive range
•will cause rapid filling of the pulmonary interstitial spaces and alveoli with
large amounts of free fluid.
Causes of pulmonary edemaCauses of pulmonary edema
Left-sided heart failure or mitral valve disease
Damage to the pulmonary blood capillary membranes

19. •Pleural effusion means the collection of large
amounts of free fluid in the pleural space.
•“edema of the pleural cavity.”

Blockage of lymphatic drainage
Cardiac failure,
Reduced plasma colloid osmotic pressure
Infection or any other cause of inflammation

20. T
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