1. Understanding Capillary
Filtration Pressure
Casey Christy, MA, ATC, CSCS

2. Key Terms
• Capillary Hydrostatic Pressure
(CHP): pressure exerted by water
in the blood which forces fluid out
of the capillary
• Tissue Hydrostatic Pressure
(THP): pressure that forces fluid
back into the capillary

3. Key Terms
• Capillary Oncotic Pressure
(COP): pressure that pulls fluid
back into the capillary
• Tissue Oncotic Pressure (TOP):
pressure that pulls fluid out of the
capillary as a result of free proteins
attracting fluid
Note that “oncotic pressure” is also known as “colloid osmotic pressure”

4. Sum of Forces
• Capillary Filtration Pressure
(CFP) is expressed as an
equation:
• CFP= (CHP+TOP) – (THP+COP)

5. Capillary Filtration
PRessure
• Here it is again spelled out:
Capillary Filtration Pressure =
(Capillary Hydrostatic Pressure + Tissue Oncotic
Pressure)
minus
(Tissue Hydrostatic Pressure + Capillary Oncotic
Pressure)

6. Capillary Filtration
PRessure
• The sum of these forces that make up
CFP determines which way fluid
travels and is also known as “Starling
Forces”
• Normal (non-injured) CFP is slightly
positive

7. Starling Forces
Tissue Oncotic
Pressure
Capillary
Hydrostatic
Pressure
Tissue
Hydrostatic
Pressure
Capillary
Tissue
Capillary
Oncotic
Pressure

8. Capillary Filtration
PRessure
• Hydrostatic forces “push” fluids
• Oncotic forces “draw” fluids

9. Capillary Filtration
PRessure
• CHP is normally positive at the
arteriolar end of the capillary, causing
fluid to move out of the capillary and
into the tissue
• At the venular end of the
capillary, forces are different to allow
resorption of fluid back into the
capillary

10. When Injury Occurs
• When an injury occurs Capillary
Filtration Pressure (CHP) changes as
a result of increased Tissue Oncotic
Pressure (TOP), causing edema
accumulation in the tissue
• Read on to see why…

11. When Injury Occurs
• When an injury occurs, free proteins
escape into the tissue as a result of
increased capillary
permeability, tissue debris, or blood
vessel bleeding
• This increases Tissue Oncotic
Pressure (TOP) which draws fluid into
the tissue resulting in edema and

12. When Injury Occurs
• Normally (no injury), 2/3 of the fluid
leaving the capillary is reabsorbed into
the capillary, and the rest is picked up
by the lymphatic system
• With an injury, this system is
overloaded since more fluid is exiting
the capillary than can be absorbed

13. When Injury Occurs
• In summary, capillary filtration
pressure increases when an injury
occurs, leading to fluid buildup in the
tissues

14. Reference
• Knight and Draper, Therapeutic
Modalities: The Art and Science