Question

Using the equation for liquid accumulation {(liquid accumulation = K [(Pc – Pi) – (Πpl - Πi)]-Q_lymph}, explain changing components in the equation can increase in interstitial volume and how edema ‘safety’ factors limit these increases.

Answer 1

This is based on the starlings forces ,

Liquid accumulation = K [(Pc – Pi) – (Πpl - Πi)]-Qlymph

Here, Pc is Capillary hydrostatic pressure

Pi = Interstitial fluid hydrostatic pressure

Πpl =Oncotic pressure of plasma

Πi = Oncotic pressue of interstial fluid

Hydrostatic pressure = Push the fulid

Oncotic Pressure = Pull the fluid

Hence, to increase the amount of interstial fluid push force i e. Hydrostatic pressure from capillary lumen should be decresed and hydrostatic pressure of interstitium should be decresed.

Also to increase the interstial fluid pull force i.e. colloid osmotic pressure should be increased in interstial fluid and decresed in capillary fluid.

So, following conditions will increase the interstial fluid and hence will cause edema.

Pc - incresed

Pi - decresed

Πpl - decresed

Πi - incresed

Decreased lymphatic flow.

Safety Factor s to prevent edema are following :::

• Increased lymph flow: Increased fluid filtration lead to increased lymph flow
• Decrease in interstitial oncotic pressure - When filtration increases, the albumin loss in the filtrate decreases. This along with Increased filterate will get washed away from interstitium.
• High interstitial compliance: large volume of fluid can accumulate in interstial without much pressure rise