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cerato
Joined: 08 Apr 2011 Posts: 1 Location: Australia

Posted: Fri Apr 08, 2011 2:17 pm Post subject: Change in blood pressure due to change in location. 


Question
You measure the blood pressure at the bicep and find that it is 140 mmHg systolic and 80mmHg diastolic. What would you expect the blood pressure to be at the top of the head given that this point is 45cm above the measurement point? Remember thisis a gauge pressure and give your answers in both mmHg and kPa. (The density of blood is about 1060 kgm^3)
This is what I have done but I am so unsure on what I am doing.
1. Converted the systolic and diastolic blood pressure into Pa.
Systolic Blood pressure= 140mmHg x 133.322Pa/1mmHg= 18665 Pa
Diastolic Blood pressure= 80mmHg x 133.322Pa/1mmHg= 10665.76Pa
2. Due to being gauge pressure I then converted to actual pressure. (this is something I am very unsure if it is needed)
P1 actual systolic pressure= 18665Pa + 101325Pa = 119990Pa
P1 actual diastolic pressure= 10665.76Pa + 101325Pa = 111990.76Pa
3. Due to the change in hieght I named the top of the head P2.
P2  P1=pg h2h1
P2=P1+pgh
P2 systolic = 119990Pa + (1060kgm^3 x 9.81 m s^2 x 45m) = 587927Pa
P2 diastolic = 111990.76 + ( 1060kgm^3 x 9.81 m s^2 x 45m) = 579928Pa
4. I then converted the P2 into kPa.
P2 systolic kPa = 587927Pa x .1kPa/100Pa = 587.9kPa
P2 diastolic KPa = 579928Pa x .1kPa/100Pa = 579.9kPa
5. I then converted the P2 into mmHg. (this seems very large)
P2 systolic mmHg = 587927Pa x 1mmHg/133.322Pa = 4410mmHg
P2 diastolic mmHg = 579928Pa x 1mmHg/133.322Pa=4350mmHg
I have spent a lot of time trying to work this out. If you can please assist me I would be very greatful. 

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hepcj Site Admin
Joined: 23 Jun 2007 Posts: 125

Posted: Sat Apr 09, 2011 11:06 pm Post subject: 


I think the problem is with your measurement of h as 45 cm. If you convert it to 0.45 m then the answer is more reasonable. 

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