Final: Lecture 23 Flashcards
Left side heart failure can cause pressure to build up in pulmonary circulation.
- Increases blood volume as much as 100%
- Increases BP
- Mild systemic effect b/c systemic blood volume is 9 times that of pulmonary system
How much blood is within the pulmonary circulation?
- 450 ml, 9% total blood volume
* 70 ml is in pulmonary capillaries
Blood getting through the lungs without being oxygenated is called?
- Physiologic shunt, about 2% in systemic arteries is blood that has bypassed the pulmonary capillaries
- Coming from lung parenchyma and left side of heart
No blood flow, local alveolar capillary never rises higher than alveolar air pressure is what zone in the lungs?
•Zone 1
Intermittent blood flow (only during systole) is ________.
•Zone 2
Zone 3 has ________ blood flow.
•Continuous
Normally, apices have _______ flow, and lower areas have _______ flow.
- Zone 2
- Zone 3
- Exercise can convert apices from zone 2 to zone 3 flow
If one lung doesn’t function what happens?
- the other lung blood flow doubles
* b/c of passive dilation of pulmonary vessels, the pulmonary pressure in the other lung is only slightly increased
Agents that constrict pulmonary arterioles.
- Norepinephrine
- Epinephrine
- Angiotensin II
- Some prostaglandins
Agents that dilate pulmonary arterioles.
- Isoproterenol
* Acetylcholine
Agents that constrict pulmonary venuels.
- Serotonin
- Histamine
- E. coli endotoxin
Sympathetic vasoconstrictor nerve fibers:
- Outflow from cervical sympathetic ganglia
- Decrease pulmonary blood flow by as much as 30%
- Mobilize blood from pulmonary reserve
During heavy exercise, blood flow through lungs increases ____ to ___.
- 4x to 7x
- Increases number of open capillaries up to 3x
- Distends all capillaries and increased flow rate up to 2x
- Increases pulmonary arterial pressure
- Pulmonary arterial pressures rises little even during maximum exercise, conserve energy to right side of heart, prevents significant rise in pulmonary capillary pressure
Left-Sided heart failure
- Pressure never normally rises above +6 mm Hg.
- blood begins to dam up in LA
- left arterial pressure rises from 1-5 mm Hg to 40-50 mm Hg
- Increased above 8 mm Hg cause equal increases in pulmonary arterial pressure, above 30 mm Hg, pulmonary edema is likely
Lung capillary fluid exchange
- Hydrostatic pressure = +7
- Interstitial fluid osmotic pressue = (-)14
- Interstitial fluid hydrostatic pressure = (-)8
- Total outward force = 29
Capillary osmotic pressure is?
- 28 mm Hg, so total inward force equals 28
* Mean filtration pressure = +29 - 28 = 1mm Hg
Excess fluid can be carried away by what?
•pulmonary lymphatics, keep alveoli dry
Pulmonary Edema
- Occurs when pulmonary capillary pressure > 25 mm Hg
- Most common cause: left-sided heart failure or mitral valve disease, damage to pulmonary blood capillary membranes
- Lethal pulmonary edema can occur within hours to minutes
What might happen when capillary pressure remains chronically elevated for two weeks or more?
•person can compensate over a period of time
Pleural Effusion
- Pumping of fluid from pleural space by lymphatics creates a normal pressure in pleural space of -7 mm Hg.
- If this pressure becomes more positive (-4 mm Hg) the lungs tend to collapse
- Pleural effusion is edema of the pleural cavity
Causes of Pleural effusion
- Blockage of lymphatic drainage from pleural cavity
- cardiac failure
- Considerably reduced plasma colloid osmotic pressure
- Infection/inflammation
Hypoxia (reduced oxygen) increased pressure in the pulmonary artery, possibly b/c of the release of ________.
•Prostaglandin
Hypoxia results in bronchial obstruction because?
- constriction of vessels supplying the poorly ventilated alveoli
- due to locally low alveolar pO2, drop in pH due to accumulation of CO2
- Decline in pH produces vasoconstriction in pulmonary vessels
- Decline in pH produces vasodilation in other tissues*
