Solving Blood Pressure Problem with Fluids: Pressure

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Homework Help Overview

The problem involves fluid dynamics, specifically relating to blood pressure and the flow of blood plasma from a bag into a patient's vein. The context includes understanding how pressure differences and fluid density affect the elevation of the bag required for the plasma to flow effectively.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the relevance of the equation for pressure in relation to the problem, questioning how to derive the necessary height for the plasma flow. There is exploration of the specific gravity of blood plasma and its implications for density calculations. Some participants suggest using consistent units and clarify the need for the density of mercury in the calculations.

Discussion Status

The discussion is active, with participants sharing insights about the relationship between pressure, density, and height. There is acknowledgment of the need for consistent units and the role of mercury's density, indicating a productive exploration of the problem without reaching a consensus on the final approach.

Contextual Notes

Participants note the requirement to express the height in centimeters and the importance of balancing pressures from the blood column and the pressure exerted by the plasma bag.

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Fluids -- pressure

Blood plasma flows from a bag through a tube into a patient's vein, where the blood pressure is 10 mmHg. The specific gravity of blood plasma at 37°C is 1.03. What is the minimum elevation the bag must have so the plasma flows into the vein?

Prof gave this problem for us to solve, and I went through my notes and didn't see much that would help me get started.
I got this equation P = P0 + density * g * h
density = mass / volume

Is this equation relevant to this problem?
Im given the pressure 10 mmHg, gravity 1.03, but what is the density?
I need to solve for height.

Can someone help me get started?
 
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'specific gravity' is the density compared to water, in this case 1.03* the density of fresh water (which is 1g/cc)
 


Oh so the density is 1.03, then g would be 9.81m/s then.
P = P0 + density * g * h
10mmHg = 1.03 * 9.81m/s * h
and solve for h?
 


Yes, make sure you have consistent units.
(You also need the density of mercury.)
 


where/how would the density of mercury come in?
Im not too sure about this.
They want the height in cm.

10mmHg = 1.03 kg/m^3 * 9.81N/kg * h
 


You have a pressure of X cm of blood pushing down from the drip.
You have a pressure equal to a column of mercury 10mm high pushing up.
These pressures have to balance, you need to find X
 

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