Cardiac Physiology - Normal Values and Equations Flashcards
How to approximate the mean arterial pressure at a normal heart rate?
MAP = diastolic P + 1/3 pulse pressure
Normal BP for an adult?
120/80
Pulse pressure?
Systolic P - Diastolic P
What equation relates flow, pressure, and resistance?
Q = ΔP/R
Equation to calculate cardiac output?
CO = HR x SV
Normal CO value?
5L/min
Normal SV for a 170 lb person?
70 mL
Formula for CI?
CI = CO / m^2
CI for 170 lb person?
CI = 5/1.5 = 3.3 L/min/m^2
Formula for SI?
SI = SV/ m^2
What is the unit of resistance?
mmHg/mL/min
Normal resistance of the systemic circulation?
0.02 PRU
1 m3 = x L?
1 L
1 L = x cm3?
1,000 cm3
1 L = x mm3?
1,000,000 mm3
Equation for ejection fraction?
Ejection fraction = SV/EDV
Equation for end diastolic volume?
EDV = SV + ESV
% of cardiac output going to the brain? VO2?
13%
VO2: = 21%
% of cardiac output going to the coronary circulation? VO2?
4%
VO2 = 11%
% of cardiac output going to the liver and GIT? VO2?
24%
VO2 = 23%
% of cardiac output going to skeletal muscles? VO2?
21%
VO2 = 27%
% of cardiac output going to the kidneys? VO2?
20%
VO2 = 7%
% of cardiac output going to the skin and other organs? VO2?
18%
VO2 = 11%
What vessels account for most of the resistance of the CV system? What to note?
- Small arteries/arterioles: 47%
- Capillaries: 27%
- Large arteries: 19%
- Veins: 7%
Highest resistance in arterioles though
Breakdown % of blood in systemic vs pulmonary circulation?
Systemic circulation => 90% of the blood
Pulmonary circulation => 10% of the blood
Pulmonary arterial pressure?
25/10 mmHg
Pulmonary MAP?
15 mmHg
Where is the largest pulse pressure found in the CV system? What is it?
LV: 120
Where is the lowest pulse pressure found in the CV system? What is it?
RV: 20
Normal venous pressure?
2-6 mmHg
Normal RA pressure?
9/4 mmHg (5)
Normal LA pressure (wedge)?
12/5 mmHg (10)
Normal RV end-diastolic pressure?
< 6 mmHg
Normal LV end-diastolic pressure?
4-12 mmHg
What is the actual equation to measure CO using the indicator-dilution technique?
I/C.T
I = mass of indicator injected C = mean dye concentration T = duration of 1st circulation
What is the Fick principle?
Amount of substance added or removed to or from an organ = blood flow x (a-v)
(a-v) = difference in concentration across the organ between arteries and veins
How is Fick’s principle used to calculate CO?
CO = blood flow across the lungs = amount of oxygen consumed (mL/min) / (a-v)O2
a = systemic arterial oxygen concentration (sampled from any artery) v = pulmonary arterial oxygen concentration
How to use the indicator dilution technique when all you have is the curve produced?
CO = amount of indicator added / area under first circulation curve
Normal RV pressure?
25/0 mmHg
Normal LV pressure?
120/0 mmHg
BV for 170 lb patient?
5L
List the distribution of BV throughout blood vessels.
- Veins: 64%
- Lungs: 9%
- Small arteries and arterioles: 8%
- Large arteries: 7%
- Heart in diastole: 7%
- Capillaries: 5%
Velocity of blood in aorta?
~30 cm/s
Velocity of blood in capillaries?
~0.1 cm/s
Equation to relate velocity, flow, and area of blood in vessels?
Flow (Q) = V x A
V = blood velocity A = cross-sectional area
Largest vessel in body? A?
Aorta
A = 4 cm^2
What is Poiseuille’s Law?
Flow equation, that expands on the original Q = ΔP/R:
Q = π.(P1 - P2).r^4/(8.η.L)
r = vessel radius η = fluid viscosity L = length of the vessel
Rearranging Poiseuille’s Law, what is the equation for resistance?
R = 8.η.L/π.r^4
How does doubling the radius of the vessel affect flow rate?
16x
Equation to calculate total peripheral resistance?
TPR = (aortic P - CVP)/CO
CVP = central venous P
Equation to calculate total pulmonary resistance (PVR)?
PVR = Pulmonary artery P - LA P/CO
Normal PVR?
0.002 PRU
How can TPR be approximated in a clinical situation?
TPR = MAP/CO
How to measure total resistance in series circuit?
RT = R1 + R2 + R3 + … + Rn
What is the pressure gradient Pi-Po equal to in series and parallel circuits?
The sum of all the pressure gradients: (Pi-P1)+(P1-P2)+(P2-Po)
What is the equation of the total flow of a circuit in parallel?
Qtotal = Q1 + Q2 + Q3 + … + Qn
How to measure total resistance in parallel circuit?
1/RT = 1/R1 + 1/R2 + 1/R3 + … + 1/Rn
Equation for Reynold’s number?
Re = ρ.D.v/η
ρ = fluid density D = vessel diameter v = mean velocity η = fluid viscosity
How can Reynold’s number predict flow?
- Re<2000 => laminar flow
- Re>2000 => turbulent flow
What is the density of blood?
1 g/mL
Equation for wall tension? What is this called?
La Place’s Law:
T = P.r
P = transmural pressure r = vessel radius
BP in capillary?
35 mmHg
How does tripling the radius of the vessel affect flow rate?
81x
Combined pressure of ejection of RV and LV?
125 mmHg
Duration of average cardiac cycle?
70 beats/min => 0.85 second cardiac cycle => 0.28 systole and 0.58 diastole
What is the aortic pressure during the isometric contraction of the LV?
80 mmHg
What % of ventricular filling does atrial contraction account for AT REST?
20-25%
What is LV EDV at rest?
140 mL
Normal ejection fraction at rest?
0.5
What is the CO during maximal aerobic exercise?
25 L/min
Max HR?
180 bpm
What is the SV during maximal aerobic exercise?
100-130 mL
What diastolic pressure is considered HT?
Above 90 mmHg
Normal PO2 of arterial blood?
95-100 mmHg
Normal PCO2 of arterial blood?
40 mmHg
Normal pH?
7.4
What is stroke work?
SV x systolic pressure
How many mL of blood need to be added to the artery for the pressure to go up 40 mmHg?
70 mL = SV to go from diastolic to systolic pressure
What is CVP at rest?
2 mmHg
Combined, what fraction of the CO do the liver and the GIT receive?
1/3
Normal arteriolar transmural pressure?
100 mmHg
What max % of CO can skeletal muscles get during exercise?
80% of 25 L/min CO
Normal MAP?
95 mmHg
Systolic RA and CVP pressure?
5 mmHg
Systolic RV and PA pressure?
25 mmHg
Systolic LA and PA occlusion pressure?
10 mmHg
Systolic LVP?
125 mmHg
Normal CI?
2.6-4.2 L/min/m^2