Lecture 23 Pulmonary Circulation Flashcards
(24 cards)
characteristics of low pressure high flow system. what is its compliance
- Wall thickness of arterial artery is 1/3 of aorta
- pulmonary arterial tree has larger compliance (7 ml/mm Hg)
What are the 2 circulations of the lungs?
1) high pressure, low flow: (oxygenated blood) from thoracic aorta to bronchial arteries to trachea, bronchial tree, adventitia
2) low pressure, high flow: (deoxygenated blood) pulmonary artery and branches to alveoli
What is the pulmonary arterial pressure and its mean?
What is the left atrium pressure?
what is the pressure gradient created between the 2?
-pulmonary arterial pressure = 24/9 mean is 15 mm Hg
-left atrium pressure = 8 mm Hg
gradient = 7 mm Hg
How much blood is in the pulmonary circulation in ml? % total blood volume in body? How much in pulmonary capillaries
- 450 ml blood pulm circulation
- 9% total blood volume in body
- about 70 ml in pulmonary capillaries
Failure of left side of heart causes pressure build up in pulmonary circulation
increases BV b 100%
increases BP
mild systemic effect bc systemic BV is 9X of pulmonary system
Physiologic Shunt: what % of blood in systemic arteries has bypassed the pulmonary capillaries and from where?
2% from lung parenchyma and wall of left atrium
When oxygen concentration in alveoli is ____ % or more below normal what happens?
- adjacent blood vessels constrict (possibly from alveolar epithelial cells)
What are the three zones of blood distriubution
zone 1: no blood flow, alveolar air pressure is always above alveolar capillary pressure
zone 2: intermediate blood flow during systole only
zone 3: continuous blood flow
What type of flow do the apices of the lung usually have
zone 2 flow
Distensibility of pulmonary veins can increase blood volume by up to ___ mL
400 (released to circulation when person stands up)
Results of obstructing blood supply to one normal lung
- Blood flow through other lung is doubled
- BC ofpassive dilation of pulmonary vessels, pulmonary pressure in lung is only slightly increased
Agents that constrict pulmonary arterioles
Some prostaglandins
Epinephrine
Angiotensin II
Norepinephrine
Agents that dilate pulmonary arteries
- isoproterenol
- acetylcholine
Agents that constrict pulmonary venules
- Serotonin
- histamine
- E. Coli endotoxin
Sympathetic vasoconstrictor nerve fibers
- decrease pulmonary blood flow by as much as 30%
- cervical sympathetic ganglia
- mobilize blood from pulmonary reserve to systemic system
During heavy exercise blood flow through lungs increases by 4X-7X.
- this increases the number of open ____ up to ____
- ___ all ____ and increases flow rate up to ___
- ___ pulmonary arterial pressure
capillaries up to 3X
distends, capillaries, 2X
increases
Why is pulmonary arterial pressure rise just a little even during max exercise?
- because the number of open capillaries is increased 3X
- all capillaries distend and increase flow rate by 2X
-this conserves energy of the right side of the hear
Left sided heart failure
-left atrial pressure is usually never above ___ mm Hg
- 6 mm Hg
- blood begins to dam and left atrial pressure rises from 1-5 mm hg to 40-50 mm hg
- increases above 8 mm hg cause equal increase in pulmonary arterial pressure. above 30 mm hg =pulmonary edema develops
Lung capillary fluid exchange
pulmonary capillary hydrostatic pressure = 7 mm hg
interstitial fluid osmotic pressure = -14
interstial fluid hydrostatic pressure = -8 (neg pressure)
total = 29
cap osmotic pressure = -28 so net 1 mm hg out
Pulmonary edema occurs when pulmonary capillary pressure is >25 mm Hg. most common cause is?
- Left sided heart failure or mitral valve disease
- damage to pulmonary blood capillary membranes
- lethal pulmonary edema can occur fast (acute)
- chronic, slow onset and lungs can adjust
Causes of plueral effusion (pumping of fluid from pleural space by lymphatics creates normal pressure of -7 mm Hg, if it becomes more postive (-4 mm Hg) lungs collapse
Plueral effusion is edema of plueral cavity
causes:
-blockage of lymphatic drainage from pleural cavity
-cardiac failure
-reduced plasma colloid osmotic pressure, and infection/inflammation
Hypoxia does what to the pressure in pulmonary arteries
increases pressure by possible release of prostaglandin
Constriction of vessels supplying poorly ventilated alveoli is from
- low alveolar pO2
- drop in pH due to accumulation of CO2
- decline in pH = vasoconstriction in pulmonary vessels which is opposite in other tissues
Reduction of blood flow to portion of lung has what effect on pCO2 and vessel diameter?
lowers alveolar pCO2 which = constriction of the bronchi supplying that portion of the lung (not as much CO2 being dropped off there)
