Key Takeaways
- Blood pressure = Systolic (heart contracts) / Diastolic (heart rests)
- Normal adult BP: Systolic 90-120 / Diastolic 60-80 mmHg
- Wrong cuff size = wrong reading (too small = falsely high)
- Position arm at heart level and allow 5 minutes rest before measuring
- Report systolic >160 or <90, diastolic >100 or <60 immediately
Blood Pressure Measurement
Blood pressure (BP) is the force of blood pushing against the walls of arteries. It is expressed as two numbers: systolic over diastolic. Accurate blood pressure measurement is a critical CNA skill.
Understanding Blood Pressure
| Component | Definition | Normal Range |
|---|---|---|
| Systolic | Pressure when heart contracts (beats) | 90-120 mmHg |
| Diastolic | Pressure when heart relaxes (between beats) | 60-80 mmHg |
| Pulse Pressure | Difference between systolic and diastolic | 30-50 mmHg |
Written as: Systolic/Diastolic (e.g., 120/80 mmHg) Spoken as: "One-twenty over eighty"
Blood Pressure Classifications (Adults)
| Category | Systolic | Diastolic |
|---|---|---|
| Normal | Less than 120 | AND less than 80 |
| Elevated | 120-129 | AND less than 80 |
| Hypertension Stage 1 | 130-139 | OR 80-89 |
| Hypertension Stage 2 | 140 or higher | OR 90 or higher |
| Hypertensive Crisis | Higher than 180 | AND/OR higher than 120 |
| Hypotension | Below 90 | OR below 60 |
Equipment
Sphygmomanometer Components:
- Cuff (bladder) - Wraps around arm
- Pressure gauge (manometer) - Shows pressure reading
- Bulb and valve - Inflates and deflates cuff
Stethoscope Components:
- Earpieces - Go in your ears (angled forward)
- Tubing - Carries sound
- Diaphragm/Bell - Placed on arm over brachial artery
Cuff Sizes:
| Cuff Size | Arm Circumference |
|---|---|
| Small adult | 22-26 cm |
| Adult | 27-34 cm |
| Large adult | 35-44 cm |
| Extra large (thigh cuff) | 45-52 cm |
Important: Wrong cuff size = wrong reading
- Too small = falsely HIGH reading
- Too large = falsely LOW reading
Manual Blood Pressure Procedure
-
Prepare:
- Have patient rest 5 minutes
- Patient seated or lying comfortably
- Arm supported at heart level
- Expose upper arm (don't roll sleeve tightly)
-
Position Cuff:
- Center bladder over brachial artery (inner arm)
- Lower edge 1-2 inches above elbow crease
- Cuff snug but not tight (two fingers should fit underneath)
-
Find Brachial Pulse:
- Locate pulse in inner elbow (antecubital space)
- Place stethoscope diaphragm over pulse
-
Inflate Cuff:
- Close valve (turn clockwise)
- Inflate to 160-180 mmHg (or 30 above expected systolic)
- Note: No sounds should be heard yet
-
Deflate and Listen:
- Open valve slightly (release 2-4 mmHg per second)
- Listen for first sound (Korotkoff sound) = SYSTOLIC
- Continue releasing
- Listen for sounds to disappear = DIASTOLIC
-
Release and Record:
- Open valve completely
- Remove cuff
- Record both numbers and arm used
- Report abnormal findings
Korotkoff Sounds
| Phase | Sound | Significance |
|---|---|---|
| Phase I | First clear tapping sound | Systolic pressure |
| Phase II | Swishing/murmur sound | Continue deflating |
| Phase III | Louder, crisper sounds | Continue deflating |
| Phase IV | Muffled sounds | Almost at diastolic |
| Phase V | Sounds disappear | Diastolic pressure |
Common Errors
| Error | Effect | Prevention |
|---|---|---|
| Wrong cuff size | Incorrect reading | Match cuff to arm circumference |
| Cuff too loose | Falsely high | Two-finger snugness test |
| Arm below heart level | Falsely high | Support arm at heart level |
| Arm above heart level | Falsely low | Support arm at heart level |
| Taking after activity | Falsely high | Rest patient 5 minutes |
| Deflating too fast | Missed systolic | Release 2-4 mmHg/second |
| Reinflating during reading | Inaccurate | Wait 2 minutes, start over |
Special Situations
Which Arm to Use:
- Use arm without IV, injury, or mastectomy
- Document which arm was used
- Use same arm for comparison
Postural (Orthostatic) Blood Pressure: Some patients need BP measured lying, sitting, AND standing to check for drops with position change.
Thigh Blood Pressure: Used when arms are inaccessible. Uses larger cuff and popliteal artery (behind knee)
Reporting Blood Pressure
Report immediately if:
- Systolic above 160 or below 90
- Diastolic above 100 or below 60
- Significant change from baseline
- Patient reports dizziness, headache, or chest pain
What does the diastolic blood pressure represent?
If you use a blood pressure cuff that is too small for the patient's arm, what will happen?
Where should the patient's arm be positioned when measuring blood pressure?