5- Measurement of Cardiac Output Flashcards
cardiac output =
heart rate x stroke volume
cardiac index =
cardiac output divided by the body surface area
load on the heart at the end of filling
preload
the amount of work it takes to move the contents of the ventricle into the aorta
afterload
the amount of tension generated is relative to the stretch on the …
muscle prior to contraction
frank starling law of the heart
the work done by the heart is directly proportional to the end diastolic volume ie the more volume returns to the heart during diastole, the more can get expelled during systole
if central venous pressure increase only a few mmHg, venous return will greatly…
diminish (becasue the driving force (pressure difference) will decrease)
when the central venous pressure equal the peripheral venous pressure…
venous return ceases = mean systemic filling pressure
what influence MSFP
ONLY volume chages
effect of dilation venous return
increase because more blood can flow into the venous circulation faster
does isolated arteriolar tone cahnge MSFP?
no
intrinsic contractile state of the heart =
inotropy
improving just the contractility of the heart will…
increase the SV
a larger preload is related to…
a larger end diastolic volume
Does the influence of arteriolar tone change blood volume?
NO
does not change the MSFP, just the rate
ie. vasodilation= higher rate return
how does blood volume influence the MSFP?
increase blood volume = higher MSFP
for the same preload, a larger afterload requires…
less shortening
a larger afterload =
larger end systolic volume
stroke volume ___________ with increasing afterload
decreases
all other things equal, if increase afterload, we will decrease stroke volume because you are unable to eject as much blood
increasing the contractile efficiecy (force generated) will ___________ the stroke volume for a similar load
INCREASE
direct Fick method
rate of oxygen consumption by a person is equal to the rate at which the oxygen comes to the organ multiplied by the amount of oxygen in the tissue
dye (indicator) dilution technique
injection of indicator into circulation with downstream blood sample
themal dilution technique
injection of cold saline blous into the RV and temperature reading in the pulmonary a.
provides ISTANTANEOUS assessment of CO
echocardiography
ultrasound image with chamber dimensions and doppler shift
principle of mass balance
from adding a known quantity of something into an unnkown volume of liquid, one can calculate the volume from the final concentration of the dye in the liquid
with known transport rate and concentration, flow rate can be calculated
