GasGasGas - The FRCA Primary Exam Podcast VivaCast 009 - Physiology - Pressure, Flow, Coronary perfusion, Cardiac Cycle
Feb 21, 2025
Dive into the intricate world of cardiac physiology! Explore how blood pressure is defined and influenced by cardiac output and vascular resistance. Discover how the Hagen–Poiseuille law affects vessel resistance, and learn the significance of viscosity and vessel length. Unravel the differences in coronary blood flow between the left and right sides of the heart. Finally, get a clear breakdown of the cardiac cycle phases, from diastole to ejection. Packed with insights, this discussion is a must-listen for anyone interested in the mechanics of the heart!
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What Determines Arterial Pressure
- Arterial blood pressure equals force over area and reflects pressure within the arterial system.
- Tom states cardiac output and systemic vascular resistance primarily govern arterial blood pressure.
Radius Has Outsized Impact
- Flow in laminar systems follows Poiseuille's law where radius has a fourth-power effect.
- Small changes in vessel radius produce large changes in resistance and thus blood pressure.
Account For Blood Viscosity Clinically
- Consider viscosity when assessing resistance: increased viscosity raises resistance in direct proportion.
- Tom highlights high haematocrit or low temperature as clinical causes of increased blood viscosity.