1a. A patient with a recently implanted heart valve suffers from an ischemic str

Question

1a. A patient with a recently implanted heart valve suffers from an ischemic stroke due to a 0.1 mm blood clot that dislodges from the biomaterial and becomes lodged in a small artery supplying blood in the brain. Brain damage occurs due to lack of oxygen, which is carried by red blood cells, and lack of glucose, which is dissolved in the blood plasma. Based on your knowledge of Darcy's law and your understanding of blood clot structure, which of these two components would you expect to be restricted first? Why? Answer in two sentences or less. length and diameter, estimate the average velocity of liquid plasma through the clot. Give your value in m/s. Clearly state any assumptions you make.

Explanation / Answer

Answer a:- Blood flow is hampered to some degree because of the clot present in the structure. The normal blood flow can be calculated by dividing the pressure gradient by vascular resistance.

The first equation of Darcy's law is

F=P/R,   (F= Blood flow)

where R = (vL/r4)*(8/P)

here, v = fluid viscosity, L= length of vessel, r = radius of vessel.

Due to presence of clot, the radius of the vessel decreases and hence resistance increases. Thus, to maintain the constant blood flow to the brain in presence of increased resistance, the pressure gradient also increases.

Thus, the two components that are restricted first are the resistance and pressure gradient.

Answer b:-

Given:- length and diameter of clot = 0.1 mm.

Now, Area of clot = 2Prh+2Pr2.

Thus Area of clot = (2*3.14*0.05*0.1)+(2*3.14*0.05*0.05)

Area of clot = 0.047 mm2.

Now, Blood Flow (F) = Mean velocity (V) x Area (A)

Blood flow through clot = 100nm2 i.e 10-6mm2

Thus,

10-6 = V x 0.047

Therefore V = 2.12*10-5mm/s

Thus, V = 2.12 *10 -8 m/s

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.