respiration - lecture 3 Flashcards
describe pathway through heart
dexoy –> right heart –> right and left pulm arteries –> lungs –> left and right pulmonary veins –> left ventricle –> pumped to whole body via aorta and small amount goes to lungs
compare pulmonary vs systemic circulation - right ventricle
right ventricle develops pressure of ~25mmhg during systole
- heart pushes blood - force - blood moves into circulation
F/A and pressure developed by right ventricle
compared to 120mmhg in right ventricle
compare pulmonary vs systemic circulation - blood pressure
blood pressure in pulmon circ is lower than in systemic
heart at same level of lungs not hard to push blood to apex
but ex : heart to fingertips = systemic, high pressure system if lungs high pressure = could get breaks in alveoli, fluid into interstitium = increases thickness of alveolar capillary membrane and decreases diffusion rate = do not want high pressure system in lungs
compare pulmonary vs systemic circulation - blood vessels
the blood vessels are thinner and have less smooth muscle than vessels in systemic circulation
offers less resistance against flow
compare pulmonary vs systemic circulation - blood pressure diagram
pulmonary = mean 15, 25/8, 25% rv, ra 2, low pressure
systemic = mean 100, 120/80, 120% lv, 5 la, high pressure, 120 = systole, relax = 80 n
pulmonary = drop of 1/10th of pressure drop in systemic (pulm~100mmhg and syst = 10mmhg)
want same amount of blood in each side (volume, vol/time = flow, same co(cardiac output))
what is flow
flow = pressure/resistance
need pressure for flow
big pipe = easy to flow fluid, small pipe = harder for same flow in same time, more resistance
blood flow in pulm = blood flow in systemic, co is equal
describe flow
total pressure drop form pulm artery to left atrium = 10mmhg
pulmonary resistance ~1/10 of systemic
describe low vascular resistance of pulm circ
low vascular resistance in pulm circ relies on thin walls of vascular system
low vascular resistance and high compliance of pulm circ allows lung to accept whole cardiac output at all times
describe accommodation of pulmonary blood vessels - specific
starting to exercise = want to increase flow, so lower resistance but not pressure since leak
pulmonary circ has capacity to accommodate 2 to 3 fold increases in co without little change in pulm arterial pressure
not all blood vessels open
describe accommodation of pulmonary blood vessels - gen
some closed at rest
does distension = wide so less resistance
and does recruitment= more blood vessels, recruit unopened ones = decreases resistance
describe what serotonin, histamine and norepi do
cause contraction of smooth muscle
increase pulmonary vascular resistance in larger pulmonary arteries
what do ach and isoproteranol do
relax smooth muscle
decreases pulmonary vascular resistance
describe reflex vasoconstriction
in regions of lung that are poorly oxygenated
what do nitric oxide do
produced by endothelial cells
relaxes vascular smooth muscle
leads to vasodilation
describe effects of gravity on pulmonary blood flow - gen
test performed by injecting radioactive xenon in peripheral vein - blood goes to lungs and diffuses and can count = more blood flow at bottom
falls down bc gravity = bottom of lungs
supine = more homogenous, at bottom and back of lungs = higher, diff value from standing up
describe starling resistor concept - top
arterial site = too low for any blood flow
squeezed so no blood flow
pressure much less
too low for any blood flow around alveoli
can be seen in disease situations
describe starling resistor concept - middle
not high enough = so capillaries squeezed
high to entrance then squeezed then blood pushes and then flows, kind on and off
blood flow but not enough, pushes and squeezes on and off
describe starling resistor concept - bottom
more pressure here
flows down pressure gradient
high more pressure then flows around alveoli = less pressure
where do capillaries go
around alveoli
pressure on alveoli - can squeeze
describe effects of gravity on pulmonary blood flow - zone 1
palv > p arter > p venous
so no blood flow
does not happen in healthy people
describe effects of gravity on pulmonary blood flow - zone 2
p arter > p alv > p venous
squeezing effect
on outlet side then blood accumulates and pushes open and then restarts
describe effects of gravity on pulmonary blood flow - zone 3
p art > p venous > p alv
blood flow increases as go down lungs
describe effects of gravity on ventilation - gen
at rest = top alveoli more open than bottom = slinky effect
take breath = all open top all the same size = change of vol at bottom greater than at top - more fresh air goes to bottom then top
breathe radioactive xenon
change in vol greater at bottom
describe effects of gravity on ventilation - specific
Gravity also affects the distribution of ventilation
In an upright lung at rest, in normal gravity, the alveoli at the top of the lungs are more opened than the bottom ones (think of a “Slinky” held in normal gravity)
the distribution of ventilation can be measured in a similar way as that of perfusion but with inhaled radioactive Xenon instead of infused in the blood.
describe distribution of ventilation perfusion ratio in the lungs in normal gravity
ratio of ventilation/perfusion higher at top of lungs
point where ratio and ventilation and blood flow meet = equal to one
not one everywhere - we are not perfect but its normal
ex on space moon = will be much more uniform since less gravity = may not be perfect stills
describe measuring pulmonary blood flow using ficks principle
O2 consumption per minute (VO2) is equal to the O2 taken up by the blood in the lungs in one minute, The [O2] in the blood entering the lungs is CVO2 and that leaving is CaO2. It then follows that:
VO2= Q (CaO2 - CVO2)
or
Q= VO2/ (CaO2 – CVO2)
where:
VO2: measured by comparing [O2] in the expired gas collected in a large spirometer and [O2] in inspired gas;
CaO2: measured from an artery;
CVO2: measured via a catheter from the pulmonary artery.
describe o2 consumed vs o2 inhaled in alveoli
equal
stays equal on right and left sides of heart
ex = cells use more o2, so p02 decreases - 30mmhg, what happens = greater pressure gradient so will diffuse more oxygen from lungs into capillary to restore equilibrium
