The pulmonary circulation has low pressure and high flow. It transports deoxygenated blood from the right ventricle to the lungs where carbon dioxide is released and oxygen absorbed. Blood then flows through the pulmonary veins into the left atrium. The pulmonary vessels are small with large elasticity to accommodate the right ventricle output. Bronchial vessels supply oxygenated blood to lung tissues. Lymphatics drain fluid and particulate matter to prevent pulmonary edema. Pressure is lowest in the right ventricle and highest in the pulmonary arteries during systole. The pulmonary capillary pressure is normally 7mmHg. Negative interstitial pressure and lymphatic drainage help keep alveoli dry. Blood flow is

1. PULMONARY
CIRCULATION
CHETANJYOT
ROLL NO:50

2. PURPOSE OF
PULMONARY
CIRCULATION
• HIGH PRESSURE
LOW FLOW
• LOW PRESSURE
HIGH FLOW
•HIGH PRESSURE LOW FLOW
•LOW PRESSURE HIGH FLOW

3. PHYSIOLOGICAL ANATOMY
Pulmonary Vessels
• 5 centimeters
• a large compliance,
averaging almost 7
ml/mm Hg, to
accommodate the stroke
volume output of the
right ventricle
• The pulmonary veins, ,
immediately empty their
effluent blood into the
left atrium.
Bronchial Vessels.
• 1 to 2 percent of the
total cardiac output.
• oxygenated blood
• empties into the
pulmonary veins and
enters the left atrium
• Therefore, the flow into
the left atrium and the
left ventricular output
are about 1 to 2 percent
greater than that of the
right ventricular output.
Lymphatics.
• right thoracic lymph
duct
• Particulate matter partly
removed
• prevent pulmonary
edema

4. • Pulmonary Vessels
• 5 centimeters
• a large compliance, averaging almost7 ml/mm Hg, to
accommodate the stroke volume output of the right
ventricle
• The pulmonary veins, , immediately empty their effluent
blood into the left atrium.

5. • Bronchial Vessels.
• 1 to 2 percent of the total cardiac output.
• oxygenated blood
• empties into the pulmonary veins and enters the left atrium
• Therefore, the flow into the left atrium and the left ventricular
output are about 1 to 2 percent greater than that of the right
ventricular output.

6. RIGHT THORACIC DUCT
PARTICULATE MATTER
PARTLY REMOVED
PREVENT
PULMOANRY EDEMA
•lymphatics

8. PRESSURE IN THE PULMONARY SYSTEM
1. Pressure in the right ventricle
The systolic pressure in the right
ventricle of the normal human
averages about 25 mm Hg,
and the diastolic pressure
averages about 0 to 1 mm Hg,
values that are only one fifth
those for the left ventricle.

9. 2 Pressure in the pulmonary artery
During systole, the pressure in the pulmonary artery is essentially
equal to the pressure in the right ventricle, However, after the
pulmonary valve closes at the end of systole, the ventricular
pressure falls precipitously, whereas the pulmonary arterial
pressure falls more slowly as blood flows through the capillaries of
the lungs
the systolic pulmonary arterial pressure normally averages about
25 mm Hg in the human being, the diastolic pulmonary arterial
pressure is about 8 mm Hg, and the mean pulmonary arterial
pressure is 15 mm Hg.

10. 3 Pulmonary capillary pressure : 7 mmHg

11. 4 Left atrial and the pulmonary venous pressure
Average 2mmHg
Range 1-5 mmHg
Measurement – pulmonary wedge pressure :
Measurement of pressure in the small branch of pulmonary artery
5 mmHg
2-3 mmHg greater than left atrial pressure
Increases in patients with congestive heart failure

12. BLOOD VOLUME OF
THE LUNGS
450 ml ie about 9% of total
blood volume of entire
circulatory system
Approximately 70 milliliters of
this pulmonary blood volume is in
the pulmonary capillaries, and
the remainder is divided about
equally between the pulmonary
arteries and the veins.

13. THE LUNGS SERVE AS THE BLOOD RESERVOIR
physiological
and
pathological
condition
one-half normal
up to twice
normal.
Hemorrhage
compensation
Cardiac
Pathology

14. BLOOD FLOW THROUGH THE LUNGS AND ITS
DISTRIBUTION
Decreased Alveolar Oxygen Reduces Local Alveolar Blood Flow and Regulates
Pulmonary Blood Flow Distribution
PO2 less than 73 mmHg in alveoli ; vasoconstriction occurs
Vascular resistance increased more than 5 times
Opposite to effect observed in systemic vessels

15. HYPOXIA
Induces vasoconstriction by inhibition of oxygen-
sensitive potassium ion channels and activation of
calcium channels
increase in pulmonary vascular resistance: important
function of distributing blood flow
if some alveoli are poorly ventilated : local vessels
constrict
blood to flow through other areas of the lungs that
are better aerated, thus providing an automatic
control system

16. EFFECT OF HYDROSTATIC PRESSURE GRADIENTS IN THE
LUNGS ON REGIONAL PULMONARY BLOOD FLOW
Length 30 cm
Pressure difference 23
mmHg
15 mmHg above and 8
mmHg below the heart

18. ZONES 1, 2, AND
3 OF
PULMONARY
BLOOD FLOW
Zone 1: No blood flow during all portions of
the cardiac cycle because the local alveolar
capillary pressure in that area of the lung
never rises higher than the alveolar air
pressure during any part of the cardiac cycle
Zone 2: Intermittent blood flow only during the
peaks of pulmonary arterial pressure because
the systolic pressure is then greater than the
alveolar air pressure, but the diastolic pressure
is less than the alveolar air pressure
Zone 3: Continuous blood flow because the
alveolar capillary pressure remains greater
than alveolar air pressure during the entire
cardiac cycle

20. 10 CM ABOVE LEVEL OF HEART TILL APEX
Apical systolic pressure
= 10 mmHg (25 mm
Hg at heart level minus
15 mm Hg hydrostatic
pressure difference)
During diastole the 8
mm Hg diastolic
pressure at the level of
the heart is not
sufficient
Therefore ZONE 2

21. 10 CM ABOVE
THE HEART TILL
BOTTOM
the pulmonary arterial pressure during both systole and diastole
remains greater than the zero alveolar air pressure. Therefore,
continuous flow occurs through the alveolar capillaries, or ZONE 3
blood flow

22. Normally : zone 2
in the apices , zone
3 in lower areas
1
Abnormal : zone 1 ;
1. upright person
breathing against
positive air pressure
2. severe blood loss
2
Person lying down :
entirely zone 3
3
During exercise :
zone 2 converted to
zone 3 in apices
4

23. INCREASED CARDIAC
OUTPUT DURING
HEAVY EXERCISE IS
NORMALLY
ACCOMMODATED BY
THE PULMONARY
CIRCULATION
WITHOUT LARGE
INCREASES IN
PULMONARY ARTERY
PRESSURE
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;
and
(3) by increasing the pulmonary arterial pressure.
This ability conserves the energy of the right side of the
heart and Prevents a significant rise in pulmonary
capillary pressure and the development of pulmonary
edema.

24. FUNCTION OF THE PULMONARY CIRCULATION WHEN THE LEFT
ATRIAL PRESSURE RISES AS A RESULT OF LEFT-SIDED HEART FAILURE
When the left side of the heart fails, however, blood begins to
dam up in the left atrium. As a result, the left atrial pressure
can rise on occasion from its normal value of 1 to 5 mm Hg all
the way up to 40 to 50 mm Hg.
when the left atrial pressure rises to greater than 7 or 8 mm
Hg, further increases in left atrial pressure cause almost
equally great increases in pulmonary arterial pressure, thus
causing a concomitant increased load on the right heart
When the left atrial pressure rises above 30 mm Hg,
causing similar increases in capillary pressure, pulmonary
edema is likely to develop

25. PULMONARY CAPILLARY DYNAMICS
• Sheet of flow
• Pulmonary capillary pressure : 7 mmHg
• Mean left atrial pressure : 2 mmHg, mean
pulmonary arterial pressure : 15 mmHg
• Time ;Normally – 0.8 sec , CO increases
, time shorten to 0.3 sec

26. CAPILLARY EXCHANGE OF FLUID IN THE
LUNGS AND PULMONARY INTERSTITIAL
FLUID DYNAMICS
LUNGS PERIPHERAL TISSUE
CAPILLARY
PRESSURE
7 mmHg 17 mmHg
Interstitial fluid
pressure
More negative Less negative
Colloid osmotic
pressure
14 mmHg Less than 7 mmHg

27. NEGATIVE
PULMONARY
INTERSTITIAL
PRESSURE AND
THE MECHANISM
FOR KEEPING
THE ALVEOLI
“DRY.
pulmonary capillaries and the pulmonary lymphatic
system normally maintain a slight negative pressure in
the interstitial spaces, it is clear that 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. The
excess fluid is then carried away through the pulmonary
lymphatics. 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