Blood Pressure Measurement for CNAs: Step-by-Step Guide and Exam Tips

Blood pressure is a measurement of the force that blood exerts against the walls of arteries as the heart pumps. It is recorded as two numbers written as a fraction. The top number (systolic pressure) measures the pressure when the heart contracts and pushes blood out. The bottom number (diastolic pressure) measures the pressure when the heart is at rest between beats. Both numbers together give a picture of how hard the heart and blood vessels are working.

On the NNAAP skills exam, blood pressure measurement is one of the most commonly selected skills from the vital signs pool. You will perform it using a manual sphygmomanometer (the inflatable arm cuff and gauge) and a stethoscope. This is different from the automatic cuffs you may have seen in pharmacies. Manual measurement requires you to listen for specific sounds and read the gauge at the right moment, which is a skill that takes deliberate practice to do accurately under exam conditions.

Why This Skill Matters on the CNA Exam

The evaluator checks that you position the cuff correctly, deflate at a controlled rate, identify both the systolic and diastolic readings accurately, and document them properly. Errors in cuff placement or deflation speed are the most common sources of point deductions. An inaccurate blood pressure reading in a real facility could lead to a patient not receiving treatment for a dangerous condition, which is why precision matters.

Normal adult blood pressure is generally considered a systolic reading between 90 and 139 mmHg and a diastolic reading between 60 and 89 mmHg. Readings outside these ranges should be reported to the supervising nurse right away. On the exam, your evaluator will expect you to state that you would report an abnormal reading even if the simulated reading is normal.

The procedure described here applies to manual auscultatory measurement using a stethoscope. Some testing sites may use electronic equipment. Check with your state's testing provider to confirm what equipment will be available on your exam date.

Understanding the Equipment

Before you can perform the skill correctly, you need to know what each piece of equipment does.

• Sphygmomanometer: The blood pressure cuff assembly, which includes an inflatable bladder inside a fabric cuff, a rubber bulb for inflation, a valve to control air release, and a pressure gauge (either a round dial or a vertical column of mercury or aneroid).
• Stethoscope: A listening device with earpieces, tubing, and a chest piece. The chest piece typically has two sides: a bell (for low-pitched sounds) and a diaphragm (for higher-pitched sounds). Both can be used for blood pressure, but many examiners prefer the bell for picking up Korotkoff sounds clearly.
• Antecubital space: The inner crease of the elbow. This is where the brachial artery runs close to the surface, which is why you place the cuff just above it and the stethoscope directly over it.
• Korotkoff sounds: The tapping and swishing sounds you hear through the stethoscope as you release cuff pressure. They appear when the cuff pressure drops below systolic and disappear when it drops below diastolic.

What You Need

• Sphygmomanometer (blood pressure cuff and gauge)
• Stethoscope
• Pen
• Paper or documentation form

Step-by-Step: Blood Pressure Measurement

1. Wash your hands. Hand hygiene before every skill is a required exam step. Identify the resident using two identifiers (name and date of birth, or name and ID band number), and explain that you are going to check their blood pressure. Asking the resident to sit quietly for a moment before you start gives a more accurate reading.
2. Position the arm at heart level with palm facing up. If the resident is seated, the arm can rest on their thigh or on a flat surface at about the same height as their chest. The palm should face upward so the antecubital space on the inner elbow is accessible. An arm hanging at the side or raised above the heart will give an artificially altered reading.
3. Expose the upper arm completely. Roll up the sleeve or have the resident remove it entirely. A rolled sleeve that forms a tight band around the arm above the cuff can restrict blood flow and affect the reading. The skin of the upper arm should be directly accessible.
4. Wrap the cuff snugly around the upper arm. Position the lower edge of the cuff approximately 1 inch (2 to 3 centimeters) above the antecubital space (the inner elbow crease). Find the marker on the cuff that indicates the center of the bladder and align it over the brachial artery. The cuff should be snug but not so tight that you cannot slide one finger underneath it. A loose cuff will give a falsely high reading.
5. Locate the brachial artery with your fingertips. Press two or three fingertips gently into the antecubital space and feel for the pulse of the brachial artery. Mark the location mentally before placing the stethoscope. This step ensures your stethoscope is in exactly the right spot to hear the Korotkoff sounds clearly.
6. Place the stethoscope over the brachial artery. Position the bell or diaphragm of the stethoscope directly over where you felt the pulse. Hold it in place with your non-dominant hand. Do not press so hard that you compress the artery. Do not tuck the stethoscope under the cuff edge, as fabric compression will muffle the sounds and lead to an inaccurate reading.
7. Close the valve on the bulb. Turn the screw valve clockwise until it is snug. Do not overtighten. Place the earpieces of the stethoscope in your ears before inflating so you can monitor for sounds throughout the process.
8. Inflate the cuff to 180 mmHg. Squeeze the bulb to inflate. Watch the gauge and stop at 180 mmHg, or 30 mmHg above the resident's last known systolic reading if you have that information. Inflating to this level ensures the cuff is above systolic pressure so you start deflating before any sounds appear.
9. Open the valve and release pressure at 2 mmHg per second. Turn the valve counterclockwise slightly to allow air to escape in a slow, controlled stream. A rate of 2 mmHg per second is the standard. If you deflate too quickly, you will hear only part of the sound range and may miss the systolic or diastolic number entirely.
10. Record the systolic reading. Listen carefully as you deflate. The first tapping or knocking sound you hear is the systolic pressure. Note the number on the gauge at the exact moment you hear the first sound. This is the first Korotkoff sound.
11. Record the diastolic reading. Continue deflating slowly while listening. The sounds will change in quality as the pressure drops. The point where the last sound disappears is the diastolic pressure. Note the number on the gauge at that moment.
12. Deflate the cuff completely and remove it. Open the valve fully to release all remaining air, then unwrap the cuff from the resident's arm. Help them return their sleeve to a comfortable position.
13. Wash hands and document both readings. Record the result as a fraction (for example, 122/78), along with the date, time, and the arm you used. Blood pressure can differ between arms, so noting which arm was used allows for consistent future comparisons.
14. Report any abnormal values to the nurse immediately. A systolic reading below 90 or above 139 mmHg, or a diastolic reading below 60 or above 89 mmHg, should be reported to the supervising nurse right away. Do not wait. In the exam setting, verbally state your intention to report an abnormal reading to demonstrate your understanding of the reporting responsibility.

What the Examiner Looks For

• Hand hygiene performed before starting
• Resident identified and procedure explained
• Arm positioned at heart level with palm facing up
• Sleeve removed or fully rolled up, no clothing under the cuff
• Cuff lower edge placed 1 inch above the antecubital space
• Cuff bladder centered over the brachial artery
• Cuff is snug but not too tight
• Brachial artery is located before placing the stethoscope
• Stethoscope placed directly over the brachial artery, not tucked under the cuff
• Cuff inflated to 180 mmHg (or 30 mmHg above last known systolic)
• Pressure deflated at approximately 2 mmHg per second
• Systolic and diastolic readings identified correctly
• Cuff fully deflated and removed after reading
• Hands washed after procedure
• Both numbers recorded with date, time, and arm used
• Abnormal values flagged for reporting to nurse

Common Mistakes to Avoid

• Cuff too loose. A loose cuff does not compress the artery properly, which results in a falsely elevated reading. The cuff should be snug enough that you can slide one finger underneath it but not two.
• Taking the reading over clothing. Even thin fabric compresses unevenly under the cuff and will cause an inaccurate result. Always expose the skin of the upper arm before applying the cuff.
• Deflating too fast. Releasing pressure faster than 2 mmHg per second means the gap between the systolic and diastolic sounds passes too quickly for you to catch. Practice with a slow, steady valve release until it becomes natural.
• Using your thumb to hold the stethoscope. Your thumb has its own pulse, and holding the stethoscope chest piece with your thumb may cause you to hear your own heartbeat instead of the patient's. Use your index and middle fingers to hold it in place.
• Not zeroing the gauge before starting. If the gauge needle does not sit at zero when the cuff is deflated, the reading will be off by however many mmHg it is displaced. Check that the gauge reads zero before inflating.
• Missing the diastolic reading by continuing to listen after sounds stop. Once the last Korotkoff sound disappears, note the number and stop. Some students continue listening and become confused about which sound was the last one. The diastolic is the point of disappearance, not any subsequent faint sound.

Printable Practice Checklist

Use this checklist when practicing with a partner or mannequin. Check off each step as you complete it.

1. Washed hands
2. Identified resident and explained procedure
3. Positioned arm at heart level, palm up
4. Exposed upper arm (sleeve removed or rolled up)
5. Wrapped cuff with lower edge 1 inch above antecubital space
6. Centered cuff bladder over brachial artery
7. Located brachial artery with fingertips
8. Placed stethoscope over brachial artery
9. Closed valve on bulb
10. Inflated cuff to 180 mmHg
11. Deflated at 2 mmHg per second
12. Noted systolic reading (first sound heard)
13. Noted diastolic reading (last sound heard)
14. Fully deflated and removed cuff
15. Washed hands
16. Recorded both numbers, date, time, and arm used
17. Identified whether values are within normal range
18. Stated intention to report abnormal values to nurse

Blood pressure measurement takes hands-on practice with real equipment. If you are looking for a program where you can train on a manual sphygmomanometer, find CNA training programs in your state.

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