Pulmonary Circulation Flashcards
The lung has how many circulations? what are they
two circulations
- High pressure; low flow circulation
- low pressure; high flow circulation
The high-pressure, low-flow circulation supplies systemic arterial blood to the
- From thoracic aorta into the bronchial arteries which supply:
- trachea
- bronchial tree (including the terminal bronchioles)
- supporting tissues of the lung (CT)
- outer coats (adventitia) of the pulmonary arteries and veins
The low-pressure, high-flow circulation supplies
- Pulmonary artery and branches to alveoli
- venous blood from all parts of the body to the alveolar capillaries where O2 is added and carbon dioxide is removed.
The pulmonary artery has a wall thickness _____ that of the aorta
1/3
All the pulmonary arterial branches have _____ diameters than their counterpart systemic arteries
larger
The larger diameter and the fact that the vessels are thin and distensible, give the pulmonary arterial tree a _______, averaging almost ______ ml/mm Hg, which is similar to that of the entire systemic arerial tree
Large compliance, 7 mL/mm Hg
What allows the pulmonary arteries to accommodate the stroke volume output of the right ventricle
Large complaince
Pressure in right ventricle during systole
25mm Hg
Pressure in right ventricle during diastole
0-1 mm Hg
Left ventricle systolic pressure
120-125 mm Hg
left ventricle diastolic pressure
0-5 mm Hg
Pulmonary artery systolic pressure
24-25 mmHg
Pulmonary artery diastolic pressure
8-9 mmHg
Mean pulmonary arterial pressure
15 mmHg
mean pulmonary capillary pressure
7 mmHg
during ______, the pressure in the pulmonary artery is essentially equal to the pressure in the right ventricle.
systole (note that it is about 25 mm Hg)
The pulmonary arterial pressure =
24/9 mm Hg
mean pulmonary arterial pressure=
15 mmHg
Left atrium pressure during diastole =
8 mmHg
What is the pressure gradient in pulmonary system
7 mmHg
Mean pressure in the left atrium and pulmonary veins is about
2 mmHg
how is mean pressure of the left atrium measured
using a pulmonary wedge
What volume of blood is within the pulmonary circulation
450mL
What % of total blood volume is in the pulmonary system
9%
What volume of blood is in the pulmonary capillaries
70mL
Failure of the ____ side of the heart can cause pressure to build up in pulmonary circulation
Left
failure of the the left side of the heart can increase pulmonary blood volume by as much as ____%. thus having what effect on pulmonary vascular pressures
100%, large increases
because the volume of the systemic circulation is about ____ times that of the pulmonary system, a shift of blood from one system to the other affects the pulmonary system ____ but usually has ____ systemic circulatory effects
9, greatly, only mild
About ___ % of the blood in the systemic arteries is blood that has bypassed the pulmonary capillaries. Why
2%. This is due to blood coming form the lung parenchyma and left side of the heart dumps into the left atrium
Blood in the systemic arteries contains ____ oxygen per deciliter than blood that has equilibrated with the alveolar air
less
When oxygen concentration in alveoli is below normal and especially when it falls below 70% (73mmHg PO2) pulmonary vessels react how
- The adjacent blood vessels constrict
- Cause of vasoconstriction is unknown but possibly vasoconstrictor released by alveolar epithelial cells
The vasoconstriction in pulmonary vessels leads to those alveoli that are poorly ventilated to get _____ blood while those with adequate ventilation get ____ blood
less, more
In the standing position, there is little blood flow to top of lungs but about ____x as much to the bottom lungs
5x
Lungs can be divided into ___ (#) of zones
3
Zone 1 of lungs
no blood flow
local alveolar capillary pressure never rises higher than alveolar air pressure
Zone 2 of lungs
intermittent blood flow (only during systole)
Zone 3 of lungs
Continuous blood flow
Lung apices have zone __ flow
2 (intermittent blood flow (only during systole)
Lower lung areas have zone __ flow
3 (continuous blood flow)
Exercise can convert apices form zone ___ to zone ___ flow
2 (intermittent blood flow only during systole) ,3 (continuous blood flow)
Distensibility of pulmonary veins makes them an important ____ reservoir
blood
- pulmonary blood volume increases by up to ____ mL. This is released to general circulation when person stands up
400mL
results of obstructing blood supply to one normal lung
- blood flow through other lung is doubled
- Because of passive dilation of pulmonary vessels, the pulmonary pressure in the other lung is only slightly increased
______ of pulmonary veins makes them an important blood reservoir
distensibility
because of the passive dilation of pulmonary vessels, when one lung is blocked blood flow to the other lung is doubled but pulmonary pressure in the lung is
only slightly increased
Agents of constrict pulmonary arterioles
- Norepinephrine
- Epinephrine
- Angiotensin II
- Some prostaglandins
Agents that dilate pulmonary arterioles
- Isoproterenol
- Acetylcholine
Agents that constrict pulmonary venules
- Serotonin
- Histamine
- E. Coli endotoxin
sympathetic vasoconstrictor nerve fibers for lungs are outflow from _______, and decrease pulmonary blood flow by as much as ___%. They also mobilize blood from ___
- Outflow from cervical sympathetic ganglia
- Decrease pulmonary blood flow by as much as 30%
- pulmonary reserve
during heavy exercise blood flow through lungs increases ____ x to ___x
4x to 7x
During Heavy exercise increases blood flow through lungs increases 4x to 7x: how?
- increases number of open capillaries up to 3x
- Distends all capillaries and increases flow rate up to 2x
- Increases pulmonary arterial pressure (slightly because the two mentioned above help prevent it)
During heavy exercise how is pulmonary pressure only increased slightly. and why is it important to maintain low pulmonary pressure
- by increasing number of open capillaries up to 3x
-distending all capillaries and increasing flow rate up to 2x
help limit the amount that pulmonary pressure rises
This is important because it conserves energy of right side of heart and prevents significant rise in pulmonary capillary pressure (thus preventing pulmonary edema) even though cardiac output is increased
Left atrial pressure is normally never above
+6mmHg
In left-sided heart failure blood begins to dam up in
left atrium
In left-sided heart failure atrial pressure rises form
1-5 mm Hg to 40-50 mmHg
Increases of left atrial pressure above ____ mmHG cause equal increases in pulmonary arterial
8mmHg
When left atrial pressure is above 30 mmHG _____ will likely develop
pulmonary edema
Pulmonary capillary pressure is
7 mmHg
Peripheral tissue capillary pressure
17 mmHg
Interstitial fluid pressure in lung is slightly more negative than that in
peripheral subcutaneous tissue
pulmonary capillaries are relatively ___ to protein molecules
leaky
Colloid osmotic pressure in pulmonary interstitial tissue is about _____ mmHg compared to less than ____ mm Hg in peripheral tissues
14 mmHg, 7 mmHg
alveolar walls are extremely
thin
Alveolar epithelium can be ruptured by any positive pressure in greater than ______ (less than ___)
alveolar air pressure (less than 0mmHg)
What is the total outward force in pulmonary capillaries
29
- hydrostatic pressure= +7
- Interstitial fluid osmotic pressure= (-14)
- interstitial fluid hydrostatic pressure= (-8)
What is the Total inward force for pulmonary capillaries
28
capillary osmotic pressure= 28
What is the mean filtration pressure for pulmonary capillaries
+29 (total outward force) + (- 28 (total inward force))
= 1 mmHg
Excess fluid in the pulmonary interstitium can be carried away by
pulmonary lymphatics
Pulmonary edema occurs when pulmonary capillary pressure is
greater than 25 mmHg
What are the most common causes of pulmonary edema
- left sided heart failure or mitral valve disease
- Damage to pulmonary blood capillary membranes
- Infections
- Breathing noxious substances
Lethal (Flash) pulmonary edema can occur
within hours or minutes
What happens when pulmonary capillary pressure remains elevated chronically (for at least 2 weeks)
The lungs become more resistant to pulmonary edema because the lymph vessels expand greatly, thus increasing their capability of carrying fluid away from the interstitial spaces perhaps as much as 10-fold (note that this is why patients with chronic mitral stenosis pulmonary pressures of 40 to 45mmHg have been measured without the development of pulmonary edema)
The pumping of fluid from the pleural space by the lymphatics create a normal pressure in the pleural space of
-7 mmHg
What creates the normal pressure of -7mmHg in the pleural space
pumping of fluid from the pleural space by the lymphatics
If the pleural space pressure increases to _____ the lungs tend to collapse
-4mmHg
_____ is edema of the pleural cavity
Pleural effusion
What are the causes of pleural effusion
- Blockage of lymphatic drainage from pleural cavity
- Cardiac failure (because this causes excessively high peripheral and pulmonary capillary pressures, leading to excessive transduction of fluid into the pleural cavity)
- Considerably reduced plasma colloid osmotic pressure
- infection/inflammation
_____ increases pressure in the pulmonary artery. How?
hypoxia. Possibly because of the release of a prostaglandin
Constriction of vessels supplying the poorly ventilated alveoli is due to
- due locally to low alveolar PO2 effect on the vessels
- Drop in pH due to accumulation of CO2
- Decline in pH produces vasoconstriction in pulmonary vessels ( note that in other tissues it leads to dilation)
Reduction of blood flow to a portion of the lung
-lowers alveolar PCO2, resulting in a constriction of the bronchi supplying that portion of the lung
