How do you measure someone's blood pressure?

How to Properly Measure Blood Pressure

To accurately measure blood pressure, have the patient sit comfortably with back supported and feet flat on floor for at least 5 minutes before taking measurements, then use a validated device with appropriate cuff size positioned at heart level, take multiple readings 1-2 minutes apart, and average the results. 1

Patient Preparation

• Have the patient relax in a seated position with back supported and feet flat on the floor for at least 5 minutes before measurement 1
• Ensure the patient has avoided caffeine, exercise, and smoking for at least 30 minutes before measurement 1
• Confirm the patient has emptied their bladder 1
• Maintain silence during the rest period and during the measurement (neither patient nor observer should talk) 1
• Remove all clothing covering the location of cuff placement 1

Proper Measurement Technique

• Use a validated blood pressure measurement device that has been calibrated periodically 1
• Support the patient's arm (e.g., resting on a desk) at heart level (the midpoint of the sternum) 1
• Position the middle of the cuff on the patient's upper arm 1
• Use the correct cuff size, ensuring the bladder encircles 80% of the arm circumference 1
• For auscultatory readings, either the stethoscope diaphragm or bell may be used 1

Taking Measurements

• At the first visit, record BP in both arms and use the arm with higher reading for subsequent measurements 1
• If systolic BP differs by >10 mmHg between arms, obtain further measurements using the arm with the higher BP value 1
• Separate repeated measurements by 1-2 minutes 1
• For auscultatory determinations:
  • Use a palpated estimate of radial pulse obliteration pressure to estimate systolic BP 1
  • Inflate the cuff 20-30 mmHg above this level 1
  • Deflate the cuff at a rate of 2 mmHg per second 1
  • Listen for Korotkoff sounds (first sound for systolic, disappearance of all sounds for diastolic) 1

Recording and Interpreting Results

• Measure BP three times with 1-2 minutes between readings 1
• Calculate the average of the last 2 measurements 1
• Record systolic and diastolic BP using the nearest even number 1
• Note the time of most recent BP medication taken before measurements 1
• Provide BP readings to the patient both verbally and in writing 1

Common Pitfalls and How to Avoid Them

• Incorrect arm position: Ensure the arm is at heart level - positioning the arm below heart level can falsely elevate readings by 5-10 mmHg 2, 3
• Incorrect body position: Be aware that supine readings may be different from sitting readings - systolic BP is often higher in the supine position by approximately 8 mmHg 3, 4
• Inappropriate cuff size: Using too small a cuff can overestimate BP, while too large a cuff can underestimate it 1
• Talking during measurement: Ensure both patient and observer remain silent during measurement to avoid falsely elevated readings 1
• Single reading: Never rely on a single reading for clinical decision-making; always take multiple readings 1
• Terminal digit preference: Avoid the tendency to round to zero by recording to the nearest even number 1

Special Considerations

• Assess for orthostatic hypotension at the initial visit by measuring BP after 1 minute and 3 minutes of standing, particularly in elderly patients and those with diabetes 1
• Record heart rate and exclude arrhythmia by pulse palpation 1
• For patients with significant inter-arm BP differences (>20 mmHg), consider further investigation for arterial stenosis or coarctation of the aorta 1