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Systolic pressure

Systolic pressure is the maximum blood pressure.

Diastolic pressure

Diastolic pressure is the minimum blood pressure.

U.S. Army Spc. Monica Brown takes a soldier's blood pressure reading at the hospital on Forward Operating Base Salerno, Afghanistan, March 10, 2008.
In routine blood pressure measurements, an inflatable cuff is placed on the upper arm at the same level as the heart. Blood flow is detected just below the cuff, and corresponding pressures are transmitted to a mercury-filled manometer. (credit: U.S. Army photo by Spc. Micah E. Clare\4TH BCT)

Calculating height of iv bag: blood pressure and intravenous infusions

Intravenous infusions are usually made with the help of the gravitational force. Assuming that the density of the fluid being administered is 1.00 g/ml, at what height should the IV bag be placed above the entry point so that the fluid just enters the vein if the blood pressure in the vein is 18 mm Hg above atmospheric pressure? Assume that the IV bag is collapsible.

Strategy for (a)

For the fluid to just enter the vein, its pressure at entry must exceed the blood pressure in the vein (18 mm Hg above atmospheric pressure). We therefore need to find the height of fluid that corresponds to this gauge pressure.

Solution

We first need to convert the pressure into SI units. Since 1.0 mm Hg = 133 Pa ,

P = 18 mm Hg × 133 Pa 1.0 mm Hg = 2400 Pa . size 12{P="18"`"mm"`"Hg" times { {"133"`"Pa"} over {1 "." 0`"mm"`"Hg"} } ="2400"`"Pa" "." } {}

Rearranging P g = hρg size 12{P rSub { size 8{g} } =hρg} {} for h size 12{h} {} gives h = P g ρg size 12{h= { {P rSub { size 8{g} } } over {ρg} } } {} . Substituting known values into this equation gives

h = 2400 N /m 2 1 . 0 × 10 3 kg/m 3 9 . 80 m/s 2 = 0.24 m. alignl { stack { size 12{h= { {"2400"`"N/m" rSup { size 8{2} } } over { left (1 "." 0 times "10" rSup { size 8{3} } `"kg/m" rSup { size 8{3} } right ) left (9 "." "80"`"m/s" rSup { size 8{2} } right )} } } {} #" "=" 0" "." "24"`m "." {} } } {}

Discussion

The IV bag must be placed at 0.24 m above the entry point into the arm for the fluid to just enter the arm. Generally, IV bags are placed higher than this. You may have noticed that the bags used for blood collection are placed below the donor to allow blood to flow easily from the arm to the bag, which is the opposite direction of flow than required in the example presented here.

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A barometer is a device that measures atmospheric pressure. A mercury barometer is shown in [link] . This device measures atmospheric pressure, rather than gauge pressure, because there is a nearly pure vacuum above the mercury in the tube. The height of the mercury is such that hρg = P atm size 12{hρg=P rSub { size 8{"atm"} } } {} . When atmospheric pressure varies, the mercury rises or falls, giving important clues to weather forecasters. The barometer can also be used as an altimeter, since average atmospheric pressure varies with altitude. Mercury barometers and manometers are so common that units of mm Hg are often quoted for atmospheric pressure and blood pressures. [link] gives conversion factors for some of the more commonly used units of pressure.

Mercury barometer has an evacuated glass tube inverted and placed in the mercury container. The height of the mercury column in the inverted tube is determined by the atmospheric pressure.
A mercury barometer measures atmospheric pressure. The pressure due to the mercury’s weight, hρg size 12{hρg} {} , equals atmospheric pressure. The atmosphere is able to force mercury in the tube to a height h size 12{h} {} because the pressure above the mercury is zero.
Conversion factors for various pressure units
Conversion to N/m 2 (Pa) Conversion from atm
1.0 atm = 1 . 013 × 10 5 N/m 2 size 12{1 "." 0`"atm"=1 "." "013" times "10" rSup { size 8{5} } `"N/m" rSup { size 8{2} } } {} 1.0 atm = 1 . 013 × 10 5 N/m 2 size 12{1 "." 0`"atm"=1 "." "013" times "10" rSup { size 8{5} } `"N/m" rSup { size 8{2} } } {}
1.0 dyne/cm 2 = 0 . 10 N/m 2 size 12{1 "." 0`"dyne/cm" rSup { size 8{2} } =0 "." "10"`"N/m" rSup { size 8{2} } } {} 1 . 0 atm = 1 . 013 × 10 6 dyne/cm 2 size 12{1 "." 0`"atm"=1 "." "013" times "10" rSup { size 8{6} } `"dyne/cm" rSup { size 8{2} } } {}
1 . 0 kg/cm 2 = 9 . 8 × 10 4 N/m 2 size 12{1 "." 0`"kg/cm" rSup { size 8{2} } =9 "." 8 times "10" rSup { size 8{4} } `"N/m" rSup { size 8{2} } } {} 1 . 0 atm = 1 . 013 kg/cm 2 size 12{1 "." 0`"atm"=1 "." "013"`"kg/cm" rSup { size 8{2} } } {}
1 . 0 lb/in . 2 = 6 . 90 × 10 3 N/m 2 size 12{1 "." 0`"lb/in" "." rSup { size 8{2} } =6 "." "90" times "10" rSup { size 8{3} } `"N/m" rSup { size 8{2} } } {} 1 . 0 atm = 14 . 7 lb/in . 2 size 12{1 "." 0`"atm"="14" "." 7`"lb/in" "." rSup { size 8{2} } } {}
1.0 mm Hg = 133 N/m 2 size 12{1 "." 0`"mm"`"Hg"="133"`"N/m" rSup { size 8{2} } } {} 1 . 0 atm = 760 mm Hg size 12{1 "." 0`"atm"="760"`"mm"`"Hg"} {}
1 . 0 cm Hg = 1 . 33 × 10 3 N/m 2 size 12{1 "." 0`"cm"`"Hg"=1 "." "33" times "10" rSup { size 8{3} } `"N/m" rSup { size 8{2} } } {} 1 . 0 atm = 76 . 0 cm Hg size 12{1 "." 0`"atm"="76" "." 0`"cm"`"Hg"} {}
1 . 0 cm water = 98 . 1 N/m 2 size 12{1 "." 0`"cm"`"water"="98" "." 1`"N/m" rSup { size 8{2} } } {} 1 . 0 atm = 1 . 03 × 10 3 cm water size 12{1 "." 0`"atm"=1 "." "03" times "10" rSup { size 8{3} } `"cm"`"water"} {}
1.0 bar = 1 . 000 × 10 5 N/m 2 size 12{1 "." 0`"bar"=1 "." "000" times "10" rSup { size 8{5} } `"N/m" rSup { size 8{2} } } {} 1 . 0 atm = 1.013 bar size 12{1 "." 0`"atm"=1 "." "013"`"bar"} {}
1.0 millibar = 1 . 000 × 10 2 N/m 2 size 12{1 "." 0`"millibar"=1 "." "000" times "10" rSup { size 8{2} } `"N/m" rSup { size 8{2} } } {} 1.0 atm = 1013 millibar

Section summary

  • Gauge pressure is the pressure relative to atmospheric pressure.
  • Absolute pressure is the sum of gauge pressure and atmospheric pressure.
  • Aneroid gauge measures pressure using a bellows-and-spring arrangement connected to the pointer of a calibrated scale.
  • Open-tube manometers have U-shaped tubes and one end is always open. It is used to measure pressure.
  • A mercury barometer is a device that measures atmospheric pressure.

Conceptual questions

Explain why the fluid reaches equal levels on either side of a manometer if both sides are open to the atmosphere, even if the tubes are of different diameters.

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[link] shows how a common measurement of arterial blood pressure is made. Is there any effect on the measured pressure if the manometer is lowered? What is the effect of raising the arm above the shoulder? What is the effect of placing the cuff on the upper leg with the person standing? Explain your answers in terms of pressure created by the weight of a fluid.

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Considering the magnitude of typical arterial blood pressures, why are mercury rather than water manometers used for these measurements?

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Problems&Exercises

Find the gauge and absolute pressures in the balloon and peanut jar shown in [link] , assuming the manometer connected to the balloon uses water whereas the manometer connected to the jar contains mercury. Express in units of centimeters of water for the balloon and millimeters of mercury for the jar, taking h = 0 . 0500 m size 12{h=0 "." "0500"`m} {} for each.

Balloon:

P g = 5.00 cm H 2 O, P abs = 1.035 × 10 3 cm H 2 O. alignl { stack { size 12{P rSub { size 8{g} } =5 "." "00"`"cm"`H rSub { size 8{2} } "O,"} {} #P rSub { size 8{"abs"} } =1 "." "035" times "10" rSup { size 8{3} } `"cm"`H rSub { size 8{2} } O "." {} } } {}

Jar:

P g = 50.0 mm Hg , P abs = 710 mm Hg. alignl { stack { size 12{P rSub { size 8{g} } = - "50" "." 0`"mm"`"Hg,"} {} #P rSub { size 8{"abs"} } ="710"`"mm"`"Hg" "." {} } } {}

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(a) Convert normal blood pressure readings of 120 over 80 mm Hg to newtons per meter squared using the relationship for pressure due to the weight of a fluid ( P = hρg ) size 12{ \( P=hρg \) } {} rather than a conversion factor. (b) Discuss why blood pressures for an infant could be smaller than those for an adult. Specifically, consider the smaller height to which blood must be pumped.

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How tall must a water-filled manometer be to measure blood pressures as high as 300 mm Hg?

4.08 m

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Pressure cookers have been around for more than 300 years, although their use has strongly declined in recent years (early models had a nasty habit of exploding). How much force must the latches holding the lid onto a pressure cooker be able to withstand if the circular lid is 25.0 cm size 12{"25" "." 0`"cm"} {} in diameter and the gauge pressure inside is 300 atm? Neglect the weight of the lid.

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Suppose you measure a standing person’s blood pressure by placing the cuff on his leg 0.500 m below the heart. Calculate the pressure you would observe (in units of mm Hg) if the pressure at the heart were 120 over 80 mm Hg. Assume that there is no loss of pressure due to resistance in the circulatory system (a reasonable assumption, since major arteries are large).

Δ P = 38.7 mm Hg, Leg blood pressure = 159 119 . alignl { stack { size 12{ΔP="38" "." 7`"mm"`"Hg,"} {} #size 12{"Leg"`"blood"`"pressure"= { {"159"} over {"119"} } "." } {} } } {}

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A submarine is stranded on the bottom of the ocean with its hatch 25.0 m below the surface. Calculate the force needed to open the hatch from the inside, given it is circular and 0.450 m in diameter. Air pressure inside the submarine is 1.00 atm.

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Assuming bicycle tires are perfectly flexible and support the weight of bicycle and rider by pressure alone, calculate the total area of the tires in contact with the ground. The bicycle plus rider has a mass of 80.0 kg, and the gauge pressure in the tires is 3 . 50 × 10 5 Pa size 12{3 "." "50" times "10" rSup { size 8{5} } `"Pa"} {} .

22 . 4 cm 2 size 12{"22" "." 4`"cm" rSup { size 8{2} } } {}

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Questions & Answers

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Sanjika
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Sanjika
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SharaAmor
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Tina
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Kanchan
psych means soul and ology means to study.
Wajid
Can someone help me with tha latent functions of different social institutions
Usman
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Interestingly Reply
Factors that affect learning?
Ofentse Reply
I am struggling with survivors guilt and complicated grief after traumatic death of spouse. how to cope.
Rowdy Reply
Try to talk with someone you trust and join people who makes you feel worthy. try to help someone. Helping someone makes you feel better
sherlock
I think you must seek professional help.
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I am extremely sorry for your loss...I know that the pain of your loss is overwhelming and that you are experiencing all kinds of difficult and unexpected emotions. please don't get me wrong but the best way to cope is to move on..i know its hard..but that's the only way..(continued.)
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Princess
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Stephanie
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Stephanie
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Stephanie
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Stephanie
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Stephanie
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Stephanie
What is meant by politics of intelligence? Please guide about this article.
Ali Reply
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Angela
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Ali
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Ali
Information about child psychology
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Jobin
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QSN Reply
neuropsychology
jeddy
behaviorism
Mira
Legal psychology
Miljana
Developmental psychology, Sports psychology , Clinical psychology , Marketing psychology , counseling psychology , Biological psychology, Educational psychology , Positive psychology etc.
Swarada
child.psychology
Nss
social, occupational psychology
jeddy
what does it mean when the temporal lobe is anterior to occipital lobe
John Reply
the cortex refers to what part of the brain
John
the cortex refers to what part of the brain
John
cerebral cortex
jeddy
behind?
jeddy
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marjelee Reply
during bad experience
Nyakuei
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gokul
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rhoda
I would think that training should be an ungoing thing. That's before, during and after. just in case there's a reoccurrence
Angela
any time
Aaronz
what is Karma
ana Reply
I think the summation of good and bad deeds you do in your life. Accidentally or otherwise.
Swarada
Yes. I totally agree.
ana
And if it is bad then the root must have been too.
ana
Yes , In Hinduism we also believe that our parent's Karma also applies to us ! Don't know about that , but it kept people in check .
Swarada
Adding to Swarada point. karma can be good or bad. both will have consequences. karma is biasedness you have shown in your life. like a king could not have two rules for normal man and his son, that comes under karma.
Sujeet
Oh perfectly said!
Swarada
Ok. It is also said that when one does something... bad or good..it will come back to you 10 folds of the same.
ana
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Swarada
karma is nothing but what one usually mean when they say- what you sow, so shall you reap.
Alisha
certainly
Crazy
more important.. this concept was told by lord Krishna as part of spirituality, to focus on your good deed ,the purpose you are born for and your responsibilities. Not for hoping that bad will happen with people who made you feel bad. just giving example ;)
Sujeet
karma is the boomerang of your actions. what u put out in the universe u get back
David
Who is the founder of psychology
Daryl Reply
Wilhelm wundt
Amanda
Wilhelm Wundt
Sneha
William wundth
Ihrar
Wilhelm Wundt
Megha
and William James
Amanda
Wilhelm Wundt
adam
Wilhelm Wundt is the founder of structuralism
Angela
Yes and also the "Father of Psychology" I think the correct word is Father not Founder.
Swarada
oh ok. noted
Angela
i believe it goes beyond him I believe it is Ancient but un formalized
David
I like your answer Swarada
David
Oh thanks! But u summarised it well!
Swarada
what is up my fellow psych peeps!!
what are some academic research on developmental psychology
Chezy
Sawrada Founder of Psychology is W.Wundt but Father of Psychology is Sigmund Freud...
Wajid
what are some good schools to study psychology?
Enjoy Reply
George Mason, Penn State, UVA, university of Michigan
Jasmine
Hi I'm currently doing my experimental psychology research can you suggest a topic or research topic for my research thank you and please see 😊
Jerico Reply
Hello Jerico. I could help you out with some ideas if you're interested!
Yasmine
can u give me some ideas too?
Geo
For sure. It depends if you're trying to do an experiment (using statistics probably) or a case study what are you aiming for?
Yasmine
Hello Jerico. Try to opt for something simple and easy to do. I wouls say perhaps study the effects of color on concentration? You could get a group of people and have them take a memory test (you can find some online) in a white room for example. Then have them take another memory test
Yasmine
similar to the first one but in a different room and then you check the responses if the performance is better
Yasmine
but you have to know that a lot of factors will interfere in the performance such as mental state etc so make sure to choose a certain specific population. that's very important
Yasmine
you could be a bit more specific about it , to isolate the variables that can mess it up like age, sex, etc... you gotta take that into account
Yasmine
so that the results get somewhat accurate
Yasmine
that is very detailed information I really like it thank you very much 😊 your so very kind
Jerico
You're very welcome
Yasmine
what are your interests in general?
Yasmine
Althogh I'm persuing botany and engineering.... but I also want to study human behaviour and psychology.... I would like if anyone can share their knowledge with me !!!!
Crazy
I'm interested on effect of electroconvulsive therapy on people having a depression
Jerico
What is Electroconvulsive therapy?
Pixeled
Astral Projection
Mansi
Electroconvulsive therapy (ECT) is a medical treatment that is most commonly used in patients with severe major depression.
Jerico
What are the expected dutties functions and responsibilities of a head of an agency based on the principles, Practice of industrial psychology?
Paul Reply
what are the psychological characteristics expected from an employee wether regular or occupying a position?
Paul
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