Haemodynamics Flashcards
What is serum
Name 3 diseases that make blood thicker/ more sludgy
Plasma without clotting factors
Polycythaemia
Thrombocythaemia
Leukemia
Are plasma viscosity changes more common than whole blood?
Name 3 proteins that affect plasma viscosity
Which of these is measured and why
- Yes
- Fibrinogen, compliment, C-reactive protein
- CRP as an indicator for inflammation
How does blood move around the body?
Compare Laminar and Turbulent Flow
What causes a change from Laminar—> turbulent
From relative high pressure to low pressure regions
Laminar: Flow is smooth, silent, maintained energy
- Slower speed at vessel edges due to resistance
Turbulent: Flow is disorganised, noisy, energy lost
Vessel narrowing (E.g stenosed arteries, Vessel branching)
Define Flow
Define Pressure
Define Resistance
Flow: Volume transferred per unit time (L/ min)
Pressure: Force per unit area (mmHG OR SI Unit- Pascal)
Resistance: Measure of difficultly of flow
Flow= k* (Change in P)
What is K, what is P
How is resistance related to K?
What is a different equation for flow
K= Conductance (Measure of ease of flow) P= Pressure
R= 1/K
Flow= (Change in P)/ R
What are the 3 main factors affecting Resistance
Which is the most important one, why?
Diameter
Length
Viscosity
Diameter is most important as;
- Length of vessels doesn’t change
- Blood viscosity is regulated within a narrow range
Which vessels have the biggest role in regulating total systemic resistance
Arterioles
Define Velocity
How is Flow related to Velocity
How does velocity change as it enters capillaries
Velocity: Distance moved by fluid in a given time
Flow= V*A (Cross-sectional area)
Capillaries have very large cross-sectional area, so to maintain constant flow, velocity decreases greatly
How do you calculate Pulse Pressure
How do you calculate Mean Arterial Pressure
What is the normal MAP?
Below what pressure is organ perfusion impaired
PP: Systolic Pressure- Diastolic Pressure (SBP-DBP)
MAP: DBP + PP/3
- 90 mmHG
- Below 70 mmHG
What is Flow also known as?
How is Cardiac Output related to Heart Rate
How is Cardiac Output related to Mean Arterial Pressure
Cardiac Output
CO= HR * Stroke Volume
MAP= CO + TPR (Total Peripheral Resistance)
What 2 factors affect Pulse Pressure
Give an example of each
Volume of blood ejected
Compliance of arterial system
Haemorrhage- Blood loss-> Reduced Diastolic pressure
Age- Arthosclerosis (Vessel stiffening)-> Reduced compliance-> Increased Systolic Pressure
Compare the 2 methods of measuring blood pressure
Direct: Precise, Invasive, Technically demanding
Indirect: Not invasive, convenient, anyone can do with minimal training
Principles rely on changes in flow type (Laminar, Turbulent)
How does stenosis affect Velocity and Flow of blood
In turbulent flow, what can be felt, what can be heard
Velocity- Increases (F=V * A)
Flow- Decreases
Felt- Thrill
Heard- Bruit
When using a cuff around the bicep and tightening then gradually loosening, what flow type is at each stage
What is heard
Loose- Laminar
Tight- No flow
Loosening- Turbulent
Loose- Laminar
Korotkoff sounds
How does gravity affect blood pressure;
Above heart level
Below heart level
When standing, why is blood pressure higher below heart
Above: Lower pressure
Below: High pressure
Gravity maintains a pressure gradient allowing blood flow from heart to foot—> Pooling of blood below heart
