syllabus p. 58: Memory tool for pressure, flow, and resistance relationships.
PQR (alphabetical). P=QR
be able to rearrange for Q =P/R; R = P/Q. used to solve for flow, resistance, and pressure. Pressure is the most tightly regulated of the 3 via pressure receptors (baroreceptors). Drop in P is due to either drop in Q or drop in R (helpful for figuring out different forms of shock (e.g., hemorrhagic vs. anaphylactic).
The figure at top of page is incorrect for mean arterial pressure. It is not 100 mm Hg when blood pressure is 120/80. Because more time is spent is diastole than systole, MAP is calculated as 2/3 Diastolic BP + 1/3 Systolic BP, so for 120/80, MAP would be about 93 mm Hg.
p. 59: blood doping may increase hematocrit too much; i.e., above the optimum hct, and cause reduced oxygen delivery due to reduced blood flow.
(Taken from Williams Hematology by Lichtman et al.
p. 60 If R = 1 for each of the resistance in series and parallel, then for the series resistances:
Rt = 1 + 1 +1 = 3
and for the parallel resistances:
1/Rt = 1/1 + 1/1 + 1/1 = 3 and Rt = 1/3
So, if you add another resistance to the parallel, Rt would = 1/4 (always gets less with added resistance)
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