Volume, pressure, resistance, flow
Volume:
- 1000 mls = 1 litres [Special authorised SI]
Pressure:
- 760 mmHg
(0°C)= 1 std Atmosphere = 101 kPa [SI]
- 1 mmHg =
1.356 cmH2O
- 1 kPa =
7.5 mmHg
Resistance:
- Resistance
is impediment to blood flow in a vessel; cannot be measured by direct
means. Is calculated from measurements of pressure difference and blood
flow within two points in a vessel
Measured in ohms
[SI]- eg: if the
pressure difference between two points is 100 mmHg and the flow is 5
l/min, then the resistance is 20 mmHg/L/min
- If this
value is multiplied by 79.9 will get the expression in dynes/sec/cm-5
Flow
- Derived
from SI units
- Movement
of a given amount of fluid in a specified time between two points
- Blood flow
is the quantity of blood that passes a given point in the circulation in a
given period of time
- Units in millilitres or litres per minute