Lecture 23 Pulmonary Circulation Flashcards
what are the two circulations of the lung?
- high pressure/low flow
2. low pressure/high flow
describe high pressure/low flow
thoracic aorta -> bronchial arteries -> trachea, bronchial tree, adventitia, CT
describe low pressure/high flow
pulmonary artery/branches -> alveoli
why do pulmonary arteries have more compliance?
they have 1/3 the wall thickness of the aorta
therefore can accommodate the stroke value of the right ventricle
which agents constrict pulmonary arterioles
norepinephrine
epinephrine
angiotensin II
some prostaglandins
which agents dilate pulmonary arterioles
isoproterenol
acetylcholine
what agents constrict pulmonary venules?
serotonin
histamine
E. coli endotoxin
what is the avg mean pulmonary arterial pressure(in mm Hg)
15
what is the avg left atrium pressure (diastole) in mm Hg?
8
effect of heavy exercise on blood flow thru lungs
flow thru lungs increase 4x to 7x
causes:
increase number of capillaries 3x
distends capillaries
increases flow rate 2x
why is it that despite an increase in blood flow through lungs during exercise, there is only a minimal rise in pulmonary arterial pressure
the increased number of capillaries and flow rate causes blood to be moved through quick enough to cause a mild/no change in the PAP
3 zones of blood flow
1: no blood flow, local alveolar capillary pressure never rises higher than alveolar air pressure
2: intermittent blood flow
3: continuous blood flow
where can we find zone 2 blood flow? zone 3?
apices
lower areas of lings
what effect does exercise have on distribution of blood through lung zones
converts the apices from zone 2 flow to zone 3 flow
effect of left sided heart failure on left atrial pressure
blood dams up causing left atrial pressure to rise from 1-5 mmHg to 40-50 mmHg
common causes of pulmonary edema
left sided heart failure
mitral valve disease
damage to capillary membranes (via infection or inspiration of noxious substances)
what capillary pressure puts a patient at risk for pulmonary edema?
30 mm Hg
forces (and values) that are included when calculating outward forces of capillaries
hydrostatic pressure (7) interstitial fluid osmotic pressure (14) interstitial fluid hydrostatic pressure (8)
Total Outward F = 29
forces (and values) included when calculating inward forces of capillaries
capillary osmotic pressure (28)
total inward f = 28
avg value for mean filtration pressure
1 mm Hg
hypoxia
reduction in O2 content/partial pressure
increases the pressure in the pulmonary artery
results of bronchial obstruction
constriction of blood vessels supplying poorly ventilated areas (lowers local alveolar PO2)
a decrease in pH during bronchial obstruction is caused by
accumulation of CO2
causes vasoconstriction in pulmonary vessels
causes vasodilation sin other tissues
results of hypoxia and bronchial obstruction
reduction of blood flow to portion of lung
decreases alveolar pCO2 = constriction of bronchi supplying that part of the long
what is the avg pulmonary arterial pressure (in mm Hg)?
24/9 mm Hg
what percentage of blood volume is in the lungs
9%
