hemodynamics 2 Flashcards
systolic pressure
peak aortic pressure
diastolic pressure
minimun aortic pressure
blood pressure is expressed as
systolic/diastolic
Pulse pressure =
Psys – Pdias = 120 – 80 = 40 mmHg
Mean arterial pressure (MAP)=
~ Pdias + ⅓(Psys – Pdias) = 80 + ⅓(40) = 93 mmHg
approximate because it depends on heart rate
Pulse pressure, mean pressure, and velocity all _____ through the vasculature.
decrease
C (vascular compliance) =
C= ΔV / ΔP
C= compliance
V is volume
P is pressure
compliance represents the
elastic properties of the vessels or chambers
compliance of arteries
absorbs energy and transforms pulsatile flow to continuous flow
____ are more compliant
veins are more compliant that arteries
compliance is determined by
relative properties of elastin versus smooth muscle and collagen in vessel walls
arteriosclerosis
when vessels lose compliance with age
older people have higher systolic pressure and higher pulse pressure than younger people
Law of LaPlace represents the
relationship between wall tension and transmural pressure
Law of LaPlace equation
T = (ΔP x r) / u
T is wall stress/tension
P is Transmural pressure
r is radius
u is wall thickness
tension in the wall increases as
pressure and radius increase
walls of larger vessels are subject to
greater tension
hypertension increases
stress on walls of vessels and chambers
an aneurysm increases
the radius of the vessel and thus increases the stress on the wall. This is why it can lead to a rupture or dissection
Law of LaPlace in the heart chambers
- decreased wall thickness causes an increased tension
2. increased radius causes an increased tension
Cardiovascular transport occurs by
- bulk transport
2. transcapillary transport
Bulk transport
refers to movement of a substance through the cardiovascular system from point A to point B
Transcapillary transport
describes the movement of a substance between capillaries and tissue
bulk transport equation
x = Q • [x]
x = rate of transport of substance x Q= flow [x]= concentration of substance x
how much O2 carried to a muscle in a minute?
Delivery in ml O2/min = cardiac output x O2 concentration
Fick’s principle is the
application of the bulk transport idea to substrate consumption by a capillary bed, a tissue, or the whole body.
simple conversion of mass: amount used is the amount in minus the amount out
Fick’s equation
Xused = Xi - Xo Xused = (Q •[x]i) - (Q •[x]o) Xused= Q ([x]i - [x]o)
Q is constant through
CV system, so it is the same for initial and final conditions.
Fick’s Principle is commonly used to determine
cardiac output and myocardial O2 consumption
Ficks equation for myocardial oxygen consumption
mVo2 = CO ([O2]a - [O2]v)
mVo2 = myocardial oxygen consumption (ml/min) CO = cardiac output (L/min) [O2]a = arterial O2 concentration [O2]v = venous O2 concentration
Fick’s equation for cardiac output
CO = mVo2/ ([O2]a - [O2]v)
