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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 h2-h1 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.
hepcj

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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