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A researcher is studying the effects of protein deprivation on edema in an animal model. He obtains the following measurements as fluid is forced out of the circulation into the tissues.

Capillary hydrostatic pressure = 20 mm Hg

Capillary colloid osmotic pressure = 15 mm Hg

Interstitial hydrostatic pressure = 6 mm Hg

Interstitial osmotic pressure = 7 mm Hg

Which of the following is the net filtration pressure?
A. – 9 mm Hg
B. – 8 mm Hg
C. – 6 mm Hg
D. 6 mm Hg
E. 8 mm Hg
F. 9 mm Hg






it has to b +6 because it's net amt going out of capillary


It is D


The answer is D.

To calculate the direction and driving force for fluid movement, use the Starling Equation

Net Filtration Pressure = (Pc– Pi) – (πc - πi)

The net pressure in this case is positive, because fluid is being forced out of the capillary.

Pc = capillary hydrostatic pressure = 20 mm Hg,
πc = capillary colloid osmotic pressure = 15 mm Hg,
Pi = interstitial hydrostatic pressure = 6 mm Hg, and
πi = interstitial osmotic pressure = 7 mm Hg.

Substituting these values into the equation and solving for the net filtration pressure, we get:

Net filtration pressure = (20 – 6) – (15 – 7) mm Hg = 6mmHg

Note: You can immediately narrow the answer options to D, E, or F because the fluid is leaving the capillaries, so the answer must be positive.


thanks for that little tip.

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