Health Assessment, part 8: Assessing Blood Pressure

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In this video and article, we explain how to assess your patient's blood pressure, some specific considerations for the assessment of blood pressure, and the expected blood pressure ranges and the levels of hypertension for adults.

This series follows along with our Health Assessment - Nursing Flashcards which are intended to help RN and PN nursing students study for nursing school exams, including the ATI, HESI, and NCLEX.

Cool Chicken When you see this Cool Chicken, that indicates one of Cathy's silly mnemonics to help you remember. The Cool Chicken hints in these articles are just a taste of what's available across our Level Up RN Flashcards for nursing students!

Systolic vs. diastolic blood pressure

When you take a blood pressure reading, you are getting two numbers — the systolic blood pressure and the diastolic blood pressure. Systolic blood pressure is the amount of pressure generated against the arterial walls during left ventricular systole (contraction of the heart). Diastolic blood pressure is the amount of pressure generated against the arterial walls during left ventricular diastole (relaxation of the heart).

When you are reading a blood pressure value, systolic is the number on the top and diastolic is the number on the bottom.

Cool Chicken Systolic is in the Sky (top number). Diastolic is in the Dirt (bottom number).

It may also help to remember your fractions—the numerator is on top, while the denominator is on the bottom. Diastolic and denominator are both on the bottom.

Choosing the appropriate arm to take blood pressure

The first step in taking blood pressure is to choose the appropriate arm on which to obtain the reading. Here are some reasons you would NOT choose a specific arm:

  • Do not take blood pressure on an arm that has a running IV infusion. Taking blood pressure on this arm would occlude the infusion, and cause pain.
  • Do not take blood pressure on an arm that has a PICC line (peripherally inserted central catheter). Taking blood pressure on this arm could cause damage or dislodge the catheter.
  • Do not take blood pressure on an arm that has an AV fistula (arteriovenous fistula), as this is a surgically created graft site where a patient may receive hemodialysis. Usually, a patient will know to give you this instruction. They might say "you can't take a blood pressure in this arm because I have an AV fistula." This is important teaching that is always given to patients who have an AV fistula. But you also need to know too. And once you've seen it, you will probably be able to recognize it in the future—but always confirm with the patient.
  • Do not take blood pressure on an arm that is on the same side that the patient has had a mastectomy. In a mastectomy, the nearby lymph nodes may also be removed or damaged, and a blood pressure cuff has the potential to cause lymphedema. If a patient has undergone a double mastectomy or there is a reason you can't use the other arm, blood pressure can be taken from the thigh.

Blood pressure positioning

When you take a blood pressure reading, the patient should be in a seated, relaxed position with their legs uncrossed and their arm at the level of their heart. Their arm should be supported, so the muscles are not straining or tense.

Blood pressure cuffs

When taking blood pressure, it is very important to select a cuff that is the appropriate size for your patient. The blood pressure cuff width should be approximately 40% of the arm circumference. The bladder of the cuff should surround 80% of the arm circumference.

A blood pressure cuff that is too small will cause a falsely high reading. A blood pressure cuff that is too large will cause a falsely low reading.

Cool Chicken If the cuff is too Large, you will get a falsely Low reading. If it is too Small, you will get a Sky high reading.

Taking a blood pressure reading

  1. Apply the (size-appropriate) blood pressure cuff snugly around the (properly positioned) patient's (appropriate) arm, 1" above the brachial artery.
  2. Palpate the radial pulse while inflating the cuff until the pulse disappears.
  3. Continue inflating the cuff an additional 30 mmHg.
  4. Place the stethoscope over the brachial artery while slowly and steadily releasing the air from the cuff. Note the mmHg reading at the first sound (this is systolic) and when the sound disappears (this is diastolic).

A "two-step" blood pressure reading that you may need to learn in nursing school involves an additional step

In the two-step method, you inflate the cuff on the patient's arm twice. Once to get to your +30 number, and again after several minutes to take the actual reading. Which method you use in nursing school will depend on what your instructors teach.

  1. Apply the (size-appropriate) blood pressure cuff snugly around the (properly positioned) patient's (appropriate) arm, 1" above the brachial artery.
  2. Palpate the radial pulse while inflating the cuff until the pulse disappears.
  3. Continue inflating the cuff an additional 30 mmHg. Note this number (e.g., if the pulse disappeared at 120, and you continued inflating up to 150, you would note 150.)
  4. Let the cuff deflate, wait several minutes, and then inflate the cuff again to your +30 number (150 in the example above)
  5. Place the stethoscope over the brachial artery while slowly and steadily releasing the air from the cuff. Note the mmHg reading at the first sound (this is systolic) and when the sound disappears (this is diastolic).

Falsely high blood pressure

These are factors that can make a blood pressure reading falsely high:

  • If the patient is talking
  • If the patient's legs are crossed
  • If the patient's arm is not supported
  • If the blood pressure cuff is too tight

Falsely low blood pressure

These are factors that can make a blood pressure reading falsely low:

  • If the patient's arm is above their heart
  • If the blood pressure cuff is too loose

Blood pressure expected ranges

Expected blood pressure ranges for adults, children, and infants are as follows:

Adults

Systolic blood pressure under 120 mmHg and diastolic blood pressure under 80 mmHg.

Children

Systolic blood pressure 90 - 110 mmHg, diastolic blood pressure 55 - 75 mmHg.

Infants

Systolic blood pressure 65 - 90 mmHg, diastolic blood pressure 45 - 65 mmHg.

Blood pressure - levels of hypertension

Levels of hypertension can be categorized into elevated blood pressure, stage 1 hypertension, stage 2 hypertension, or a hypertensive crisis.

Elevated

Systolic blood pressure 120 - 129 mmHg and diastolic blood pressure less than 80 mmHg.

Stage 1 Hypertension

Systolic blood pressure 130 - 139 mmHg, or diastolic blood pressure 80 - 89 mmHg.

Stage 2 Hypertension

Systolic blood pressure 140 mmHg or higher, or diastolic blood pressure 90 mmHg or higher.

Hypertensive Crisis

Systolic blood pressure higher than 180 mmHg and/or diastolic blood pressure higher than 120 mmHg.

Quiz Questions

The nurse knows that using a blood pressure cuff that is too large will result in which type of a reading?

This will cause a falsely low reading.

When during a blood pressure reading should the nurse record the systolic blood pressure?

Upon hearing the first sound, the nurse should record the systolic blood pressure.

Which of the following are reasons to avoid using an arm for a blood pressure?

Presence of an AV fistula, ipsilateral mastectomy, or a running IV infusion.

Full Transcript: Health Assessment, part 8: Assessing Blood Pressure

Hi. I'm Meris. And in this video, I'm going to be talking to you about how to assess your patient's blood pressure, some specific considerations for the assessment of blood pressure, and I'll also be going over the expected blood pressure ranges and the levels of hypertension for adults.

I'm going to be following along using our health assessment flashcards. These are available on our website, leveluprn.com. And if you already have a set of your own, I would invite you to go ahead and pull them out and follow along with me. All right. Let's get started.

All right. First up, let's go ahead and talk about the actual assessment technique for obtaining a blood pressure. So some different considerations that we need to think of.

First is, we need to choose an appropriate arm to obtain the blood pressure on. So these are some reasons that you would want to avoid using your patient's arm, given arm, whichever one it is. Here are some reasons.

So if the arm has a running IV infusion, we don't want to use the blood pressure. It will occlude that infusion. It can cause pain over the site. There's a lot of reasons we want to avoid that.

If they have a PICC line, a Peripherally Inserted Central Catheter, in that arm, avoid that arm, right? We don't want to cause any damage to it. We don't want to dislodge that catheter. All kinds of reasons.

An AV fistula, an arteriovenous fistula, which is, it's going to be in your patient's arm typically right around here, sometimes it can be a little higher. And it is a surgically created graft site where a patient may receive hemodialysis. And they will know this, "Oh, you can't take a blood pressure in my arm." But you need to be aware of this as well. Ask them if they have a fistula. And if you see that, and usually you can tell - once you've seen one, you kind of know what they look like - you need to say, "Is that an AV fistula? Because then I need to use the other arm."

And if we have had a mastectomy on that same side. So an ipsilateral, meaning on the same side as the arm, mastectomy is a reason to avoid taking a blood pressure because we can lead to-- we can cause lymphedema if we take a pressure there.

So we want to have the patient in a seated, relaxed position with their legs uncrossed and their arm at the level of the heart.

This is the thing that is done wrong the most in clinical practice, but that arm should be at the level of the heart.

It's also important to make sure that I am selecting a cuff that is the appropriate size for my patient. So for instance, at my facility, we have radial cuffs, small adult cuffs, adult cuffs, and large adult cuffs. And I need to make sure that I'm picking one where the blood pressure cuff width is going to be approximately 40% of the arm circumference. So it can't just measure up, right? I can't have just a little bit of overlap. I want the patient's arm circumference to take up about 40% so that I still have enough left over for that kind of wiggle room.

You know that's important because we put it here in bold red text. Why does this matter? I'm so glad you asked. I can't wait to tell you.

We also have a cool chicken here to help you remember this.

If you have a cuff that is too large for your patient, L for large, you will get a falsely low reading. If the cuff is too small, S for small, you will get a falsely sky-high reading.

So why does this matter? Well, for instance, if I use a cuff that's too large, I might get a falsely low reading and I won't know that my patient maybe has hypertension, or vice versa. If I use a cuff that is too small, maybe I will miss the fact that my patient is actually experiencing hypotension. So I can miss some crucial information and just not have an accurate reading if I don't use the right cuff size.

All right. Now when we talk about two-step blood pressures, this is likely what you're going to have to do in nursing school. This is not something that I routinely have to do in my own clinical practice. But for your edification, when we are taking a two-step blood pressure, we're going to put that blood pressure cuff around the patient, and then I'm going to palpate their radial pulse while I inflate that cuff, okay? And what I'm going to do is I'm going to keep inflating until I no longer feel that pulse. And when that pulse disappears, I'm now going to inflate the cuff an additional 30 millimeters of mercury, okay? So when the pulse disappears, go up 30 more. So that's step one.

And if you're doing a true two-step, you're going to let the cuff deflate, you're going to wait several minutes, and then you're going to inflate that cuff up to that determined number. So I felt the pulse disappear at 120, so I'm inflating to 150.

Now, we're going to place our stethoscope over the brachial artery and slowly and steadily release the air from that cuff. If you do it too quickly, you will not be able to get an accurate reading because you're going too fast. I can't tell when I'm hearing those sounds. I'm going to listen for the first sound that I hear. And that very first sound that I hear is going to be where I will record in my head the systolic blood pressure reading. So I'm slowly letting the air out of that cuff and at 124, I hear [a pulse sound]. That's the first sound I hear. I'm going to think in my head, "124. 124." I'm going to continue listening until I no longer hear the sound. So when that sound disappears, that number is your diastolic number. And that's how we obtain the blood pressure.

Now, let's talk about some expected blood pressure ranges, and then we'll move on to some unexpected findings. Expected blood pressure ranges. I'm going to give you the same disclaimer I've given you before. This is based on curating a whole bunch of peer-reviewed sources out there, but whatever your facility or your school or your professor says is correct. Just scratch it out and write the figure that you need to know. It's okay. There is going to be some variation, okay?

But for adults, and this is bold and red because this is the one that you really got to know the most, we expect the systolic blood pressure to be less than 120 and the diastolic blood pressure to be less than 80 millimeters of mercury, okay? That is the expected finding.

And again, this is more important for peds, but I'm just going to tell you, children, we expect the systolic to be 90 to 110 millimeters of mercury with a diastolic of 55 to 75 millimeters of mercury.

And infants, we expect that systolic to be between 65 and 90 millimeters of mercury and diastolic of 45 to 65 millimeters of mercury. C

hildren and infants have lower blood pressures than adults. So be aware of that. Be prepared to have that as a finding.

Now, when it comes to remembering systolic and diastolic, this can get tricky for a lot of people if they've never had this experience before. I always think of it as stalactites and stalagmites. It can get confusing because they sound very similar.

So we have a cool chicken right here as well. Systolic is in the sky. S and S. Diastolic is in the dirt. So the systolic is on top, right? That's that top number. Diastolic is on bottom. Sky and dirt, okay?

All right. Now let's talk about levels of hypertension for adults.

So an elevated blood pressure is a systolic of 120 to 129 and a diastolic that is still less than 80 millimeters of mercury. For instance, I might have a little elevated blood pressure when I go to the doctor because I'm nervous, right? But it doesn't necessarily mean that I have hypertension.

Stage one hypertension, systolic blood pressure between 130 and 139, or a diastolic pressure of 80 to 89. Note that I said or because we can have just diastolic hypertension.

Stage two hypertension is going to be a systolic greater than or equal to 140 millimeters of mercury or a diastolic blood pressure greater than or equal to 90 millimeters of mercury.

And then this one, I see this very frequently as an ER nurse, a hypertensive crisis is technically when your patient has a systolic pressure greater than 180 millimeters of mercury and/or a diastolic greater than 120 millimeters of mercury. So be aware of that. As you are studying throughout med-surg, fundamentals, all of these different courses, think about what those interventions might be if you had a patient with stage one, two, or a hypertensive crisis. Think about what you would do for those patients.

All right. Now let's test your knowledge of some key facts provided in this video with my quiz questions.

The nurse knows that using a blood pressure cuff that is too large will result in which type of a reading?

This will cause a falsely low reading.

When should the nurse record the systolic blood pressure?

Upon hearing the first sound, the nurse should record the systolic blood pressure.

Which of the following are reasons to avoid using an arm for a blood pressure?

Presence of an AV fistula, ipsilateral mastectomy, or a running IV infusion. All of these are reasons to avoid using a specific arm to obtain a blood pressure.

All right. That is it for blood pressure. I hope that this review was helpful to you. If it was, I would love to hear your comments. And if you have a better way to remember something, I want to hear it and I know that your classmates do too. So be sure to leave me a comment so that I can see that. What you're doing is really hard, and I know it can be exhausting, but you are doing a great job, and I'm super proud of you. Thanks for studying with me.

All right. A little clinical tip from me to you. If you put that blood pressure cuff on your patient's arm, and you can just tell already that it's the wrong size, don't waste your time getting that blood pressure, just go get the right cuff size. And that sounds really self-explanatory, but when we're in a rush or when things are busy, and we're overwhelmed or this patient's got a lot going on, it can be easy to be like, "Just get the blood pressure and we'll figure it out later. I'll get a new cuff later." Don't do that because now we're not getting correct information, and you're going to end up needing to get it anyway. Especially if it's too small, that cuff's going to inflate and pop off of your patient's arm, okay? So just get the right cuff from the beginning. [laughter]

Okay. A second tip for you, and this is so cool. When you are using an automatic blood pressure cuff, this is something that many people may not actually know, it doesn't actually accurately calculate the systolic and the diastolic blood pressure. What it's doing is it is measuring your mean arterial pressure, MAP, and then it reverse engineers the systolic and diastolic blood pressure.

So, if you are looking at your patient's MAP on the monitor, that is the most accurate part of the blood pressure assessment when you're using an automatic cuff. So if you're looking at that blood pressure, and you think, "That just can not be right," get a manual to confirm. You will be surprised. The numbers might be wildly different, but that MAP may be bang on exactly the same.

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