Blood Pressure Explained (Nursing Physiology)

Aug 24, 2023

Blood Pressure Explained (Nursing Physiology)

Blood pressure is the amount of force caused by blood pressing against the walls of your arteries. It is the sum of heart rate per minute, the volume of blood pumped out with each contraction, and the resistance the heart needs to overcome.

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Heart rate is measured by taking a patient’s pulse measurement and it can be impacted by a variety of physiological and psychological factors. While the sinoatrial node controls the heart rate, it is influenced by physiological, psychological, and environmental factors.

The electrical conduction of the heart can be reviewed here    • Electrical Conduction System of the H…

Heart rate is known to elevate during times of activity, stress, and excitement. It can also be affected by illness, disease, and hormones.

Stroke volume is affected by the amount of blood that can enter the ventricle during atrial systole and many factors can affect the completing emptying of the atrial and the compliance of the ventricles. Preload is the term we use to explain the volume of fluid that enters into the ventricles. In a normal heart, it is estimated to be approximately 70 ml.

The heart sounds are created by the opening and closing of these valves and you can learn more here    • How to Hear S1 and S2 Heart Sounds

Peripheral resistance (PVR) is a term used to describe how much pressure the heart has to exert in order to overcome the vessel size and compliance. Factors such as atherosclerosis and vasoconstriction will increase the PVR.

To review the blood flow through the heart,    • Blood Flow Through the Heart (Circula…

Systolic and diastolic blood pressure and defined and hypertension stage 1 and 2 are reviewed.

Additionally, the role of the baroreceptors in the carotid arteries and the renin-angiotensin-aldosterone pathway are touched on to provide an overall view of the factors that affect blood pressure.

Content

0 -> Hi guys. It is Tammy with NurseMinder and today we're going to be talking

4.17 -> about the elements that help to create and maintain our blood pressure.

10.849 -> Specifically we'll be looking at the three things that influence blood

14.7 -> pressure and the two systems in our body that help us to maintain it. And we're

19.71 -> going to take care of all of that, right after this. Welcome back my name is Tammy

31.71 -> and this is NurseMinder and on this channel we do everything nursing so if

36.329 -> you're new here consider subscribing below so that you get the next video

39.809 -> when it's released. Have you ever wondered what's going on inside your

42.66 -> body that's actually regulating your blood pressure? Maybe you've gone to

46.35 -> those drug stores where you put your arm into the automated machine and it

49.95 -> squeezes really hard and seems to last forever but the readings that you get

53.91 -> are either always different or really really different? Well there's a few

59.07 -> things that are happening inside the body that are helping to regulate that

62.489 -> blood pressure, and we want to talk about those next. Now be sure to stay to the

66.81 -> end of the video because I will be talking about some of the things that

69.869 -> are often tested in nursing exams and things that patients often ask about. So

76.71 -> we'll do that after at the end. Now blood pressure is really a summary of three

83.64 -> things happening in the cardiovascular system. One is our heart rate which is

87.75 -> measured per minute. The second is our stroke volume and that's how much blood

91.92 -> is squeezed out of the heart with every contraction . And the third is peripheral

96.659 -> resistance and this is those arteries that the blood is being pumped into - how

100.59 -> willing are they to accept that blood and how much are they resistant. So if

104.97 -> I were to give an analogy, for example it's really windy today, this would be

109.71 -> considered how many steps I take in a minute under normal conditions, stroke

116.579 -> volume is the distance between my steps - so how far I am covering, and then that

122.61 -> resistance would be, today's really windy it's super windy, and so I have to work

126.509 -> much harder to get the same distance. That would be a good analogy to share

130.86 -> with your patients. Now in terms of heart rate, there's many things that can

135.42 -> impact heart rate and it is driven in particular by two nerves in the heart -

139.92 -> and that is the vagal nerve and the accelerator nerve. The vagal nerve is

145.23 -> what slows the heart rate down so when you go to sleep or when you're like oh

151.04 -> bear down, holding your breath, it will slow the heart rate. And the accelerator

155.37 -> nerve is what increases it. So these two work in tandem but there's a host of

159.96 -> things that can impact our heart rate which will change our cardiac output and

163.56 -> will influence our blood pressure. Now I just have a small list here, this is not

168.78 -> exhaustive, but activity as we know exercise increases the heart rate.

175.19 -> Hydration. If you're dehydrated in particular then our heart rate will

179.94 -> increase to supplement that movement of fluid. Our oxygenation status- if we are

186.63 -> deficient in oxygen again the heart rate will increase to impact our cardiac

191.16 -> output. If you are under stress- increased heart rate. Our thyroid, we can that hyper or hypo

197.73 -> thyroid and so there's some other medical conditions that will influence the

201.12 -> functioning of the heart rate - illnesses and medications. So you can see there's a

206.73 -> variety of things that can influence just this one factor. Factors that affect

211.65 -> stroke volume included how much fluid is coming into the ventricle. So we call

215.82 -> this preload. And then there is the heart's ability to actually contract strong

225.15 -> enough to eject that fluid out, so potentially you may be heard people who

229.95 -> have have heart failure or increased heart size those are things that would

235.47 -> affect stroke volume. So ventricular hypertrophy would be an example. And then

242.13 -> factors that influence peripheral resistance. So this is the after load. This

246.3 -> is the pressure that the heart needs to generate in order to pump that blood out.

250.65 -> So I am going to write after load.

255.959 -> But this would be the vessel size and how willing it is to accept it, so how

260.44 -> compliant is it and again there's a whole host of diseases that can create

271.47 -> compliance issues so athero, atherosclerosis is a common one. That's

275.92 -> plaque in your vessels that will make those vessels more rigid that they don't

280.3 -> have that stretch capacity to take fluid into it. And so here we have a variety of

285.43 -> things can affect these three main elements of blood pressure .Now of course

290.62 -> some of this peripheral resistance can be affected by some of the things that

294.22 -> affecting heart rate so if I'm under stress, I've got that sympathetic nervous

297.22 -> system fight or flight going, my vessels constrict and it will influence the

301.72 -> resistance at which the heart is pumping against. Okay so now let's talk about

305.92 -> what a blood pressure reading is. So it's measuring that pressure inside the

309.76 -> system as a result of heart rate stroke volume and resistance and we end up with

315.43 -> what's call the systolic number and a diastolic number. Now you notice that the

319.6 -> systolic vessel is wider than my diastolic and that's for a very

325.27 -> important reason. Imagine you're hooked up to a water hose and we turn on the

330.13 -> tap. All that pressure is coming through and so this is really my water hose here

335.26 -> and it's turned on and we have maximum pressure in here. So if you were to go

343.419 -> and step on that garden hose you wouldn't be able to really manipulate it

346.81 -> because it's full and it's tense. Well when you turn the top off, the pressure

352.09 -> goes down but it doesn't eliminate the water that stays in the hose or in the

357.1 -> vessel, there's still some water there and this would be our diastolic pressure.

361.05 -> So systolic is the amount of pressure in the vessel when it is in contraction and

367.38 -> diastolic is when the vessel is relaxed. You'll hear a lot about these numbers

372.07 -> 120 over 80. Now we know there's been a lot of changes recently with the

376.45 -> guidelines for high blood pressure but typically 120 and less is considered

381.19 -> normal for systolic and 80 or less is normal for diastolic . So you can see here

388.25 -> that the normal blood pressure is now considered to be less than 120 over 80.

392.3 -> There's my systolic and my diastolic. And elevated blood pressures now between the

397.19 -> readings of 120 and 129. Hypertension is when we now see a reading of 130 to 139

404.78 -> and we're starting to see changes in our diastolic so eighty to eighty nine

408.71 -> milligrams of mercury. Stage two hypertension is anything greater than

413.38 -> 140 over 90 diastolic or higher. Okay now the other two systems that are

420.77 -> working in our body to help us maintain our blood pressure are what's known as

425.44 -> baroreceptors and the renin-angiotensin-aldosterone system. Now

431 -> I will talk about this in another video but just to give you an overview of these

434.84 -> two systems. The baroreceptors are measuring pressure, so the stretch that

440.06 -> exists in those vessels ,and in particular there's two places. One is

444.26 -> just off the heart as it's leaving, as the blood is leaving the ventricle to go

448.88 -> to the body we have a baroreceptor. And the other is off the carotid

453.14 -> arteries as its heading towards the brain because the brain likes to be

456.74 -> perfused. This one, okay so coming back baroreceptors, are looking for pressure

461.3 -> and that will affect the vessel size and heart rate.

464.06 -> The RAAS system- the renin-angiotensin-aldosterone system

468.85 -> will be also assessing for pressure but it's going to be focused on maintaining

473.03 -> water and sodium in the system should our blood pressure go low, and getting

477.89 -> rid of it should our blood pressure be too high. So there's a quick summary of

485.75 -> the elements and systems in place already in our body to help us regulate

490.58 -> our blood pressure. Okay as promised I mentioned at the end of this video I

495.41 -> would talk about what is often tested for students and nursing exams and what

500.66 -> patients often ask about. And to summarize it - its cardiac output! You're

506.09 -> going to want to remember the factors that affect cardiac output. So heart rate x

509.48 -> stroke volume and that blood pressure is also with - also has the

515.81 -> element of peripheral resistance. So when you put those things together, any

519.56 -> question you have that is looking at the patient's cardiovascular system will

523.34 -> be looking for those elements. Patients will also ask about cardiac output, but

529.64 -> they don't phrase it that way. They'll ask you what is blood pressure and so

533.99 -> I've given you the hose analogy so that when you need to explain what systolic

538.76 -> and diastolic is and what a normal blood pressure would be, you have that prepared.

545.14 -> The second NCLEX thing that we tested on is the hypertension treatment scale. So

551.24 -> you want to be making sure you recognize what is elevated blood pressure, what is

555.2 -> considered to be hypertension stage 1, stage 2, and what would be normal. Now be

562.19 -> sure to watch the next video on the renin-angiotensin-aldosterone system and

566.54 -> the baroreceptors so you get a little bit more insight

569.69 -> into how they're really working behind the scenes to make sure our blood

572.81 -> pressure stays in that safe range so our body is perfused well with hydration and

578.39 -> nutrition. And until next time guys, make it a great day :)

Source: https://www.youtube.com/watch?v=p7H5v5vm7JM