The Physical Rules
of the Heart, Blood Flow, and Cardiac Output
Week 14: The Heart, Cardiac Output, and Blood Flow Physics
1. Physics of Blood Flow: 4DMRI
1. How can a ‘strong contraction’ of the left ventricle improve flow, reduce friction, and reduce ‘clogs’?
- vortical flow or spinning blood reduces friction, charges the vessel wall, which in turn repels calcium away from the wall.
see: Fred Kummerick, Riddick, and Steiner
- A strong contraction and a fuller volume of blood go together. Starling’s Law.
2. How does fat(ty acid) figure into the 3 phases of ‘oxidative stress’ or ‘free radical chain reaction’?:
SHOW GRAND SCHEMATIC
- Oil painters,wood deck varnish, gummed carb, ethane pentane gas, more
Q. What makes a strong muscle weaken?
overuse. Heart stats:
6Kg ATP/day (20-30 x its own weight)
10 tons of blood/day
Feed cells specifically for their particular energy need (Heart, Nerves (Brain), Skeletal Muscle, Gut cells, etc
Energy Starvation Model:
The failing heart is an engine out of fuel
2. Demonstration: Directly measuring O2 removed from blood
1 Mason jar
20 marbles or beads
Calculation of (a-v) O2 difference:
Assume we extract a wad of freshly oxygenated arterial blood (100ml) the moment it leaves your heart.
- This blood holds 20ml of dissolved O2.
Oxygen is removed as blood circulates.
Now we measure the O2 remaining in blood just before it returns to the heart.
At rest: 8ml O2 is removed during aerobic metabolism.
- a-v O2 diff = 12. (20-8 = 12)
At max intensity: 16ml O2 removed
- a-v O2 diff = 4. (20-16 = 8)
3. Stroke Volume, Cardiac Output, and Calculating VO2 Consumed per Minute
How to calculate cardiac output.
- Cardiac output is the volume of blood pumped per minute
Cardiac Output = Stroke Volume x Heart Rate
- An untrained person’s heart pumps out approximately 60ml blood per beat. This is stroke volume.
- Assume we measure resting heart rate in an untrained person at 70 bpm (beats per minute)
- Thus, 60ml blood is pumped out 70 times in one minute.
Cardiac output is 60 ml x 70 BPM = 4,200ml/min.
How to Calculate Oxygen Uptake at Rest
- Assume we use the same untrained person from above:
Total blood ejected per minute:
70BPM x 60ml = 4,200 ml/min
We know by directly measuring blood that 8ml/O2 is removed from a wad of blood returning to the heart. (Calculated in previous section)
- The ‘truck load’ or wad of blood is = 100ml of liquid (recall O2 gas dissolves in liquid)
Blood is flowing continuously into the heart – and in 1 minute, 4200ml blood actually returned to the heart – which is 42x greater than 100ml.
- A proportional amount of oxygen (42x more) is also removed in 1 min.
42 x 8ml = 336ml/min. –> 1 MET