Lecture 23: Pulmonary Circulation and Gas Exchange Flashcards
What is the circulation of high pressure; low flow in the lungs?
thoracic aorta- bronchial arteries- trachea, bronchial tree, adventitia, CT
What is the circulation of low pressure, high flow?
pulmonary artery and branches- alveoli
What is pulmonary arterial pressure?
24/9 mm Hg
What is mean pulmonary arterial pressure?
15 mm Hg
What is left atrium pressure?
8 mm Hg
What is the pressure gradient in pulmonary system?
7 mm Hg
What is the mean pressure in left atrium?
2 mm Hg
Failure of the ___ side of the heart can cause pressure to build up in pulmonary circulation
left
What is the physiologic shunt?
2% of the blood in the systemic arteries is blood that has bypassed the pulmonary capillaries, blood coming from the lung parenchyma and left side of the heart
What happens in oxygen concentration in alveoli is 70% or more below normal?
adjacent blood vessels constrict
caused by unknown vasoconstriction
how much blood flow is in zone 1
no blood flow; local alveolar capillary pressure never rises higher than alveolar air pressure
how much blood flow is in zone 2
intermittent blood flow
how much blood flow is in zone 3
continuous blood flow
What are agents that constrict pulmonary arterioles?
norepinephrine
epinephrine
angiotensin II
some prostaglandins
What agents dilate pulmonary arterioles?
isoporterenol
acetylcholine
What agents that constrict pulmonary venules?
serotonin
histamine
e coli endotoxin
Why does pulmonary arterial pressure rise only a little during maximum exercise?
because the number of open capillaries increases 3x and all capillaries distends and increases flow rate up to 2x
What happens in left heart failure?
blood begins to dam up in left atrium
left atrial pressure raises from 1-5 mm Hg to 40-50 mm Hg
increases above 8 mm Hg cause increases in pulmonary arterial pressure
above 30 mm Hg, edema likely to develop
pulmonary capillaries are relatively ______ to protein molecules
leaky
When does pulmonary edema occur?
when pulmonary capillary pressure > 25 mm Hg
What causes pulmonary edema?
left sided heart failure or mitral valve disease
damage to pulmonary blood capillary membranes: infections, breathing noxious substances
What is pleural effusion?
edema of the pleural cavity
What is the causes of pleural effusion?
blockage of lymphatic drainage from pleural cavity
cardiac failure
considerably reduced plasma colloid osmotic pressure
infection/inflammation
Hypoxia increases pressure in the ____ artery due to what?
pulmonary; release of a prostaglandin
What is the result of bronchial obstruction?
constriction of vessels supplying the poorly ventilated alveoli
What causes bronchial obstruction?
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
decline in pH produces vasodilation in other tissues
What are the factors that affect rate of gas diffusion?
solubility of gas in fluid cross sectional area of the fluid distance through which the gas must diffuse molecular weight of gas temperature of fluid
What is oxygen concentration in the alveoli and partial pressure controlled by?
rate of absorption of oxygen into the blood
rate of new oxygen entry into the lungs
alveolar PCO2 increases in _____ proportion to rate of excretion
direct
alveolar PCO2 decease in _____ proportion to alveolar ventilation
inverse
What factors determine how rapidly a gas will pass through the respiratory membrane?
membrane thickness
membrane surface area
diffusion coefficient of gas in the substance of the membrane
partial pressure difference of gas between the two sides of the membrane
What is the ventilation perfusion ratio?
Va/Q= alveolar ventilation/ blood flow
Va/Q is normal when both factors are _______
normal for a given alveolus
