Deconstructing JNC 7 – Part 5

Correct BP Measurement

According to JNC 7, mercurial sphygmomanometer remains to be the standard upon which all other devices of BP measurement must be compared to. Nonmercurial sphygmomanometers are popular and safe but must always be calibrated.

Patient should have at least 5 minutes of rest in a chair, feet on the floor and arms at heart level. Caffeine, exercise, and smoking should be avoided 30 minutes prior. Appropriate cuff bladder size would be at least 80% percent of the arm. Palpation of the RADIAL pulse obliteration should estimate systolic BP. Auscultate 20-30 mmHg higher than this level. DEFLATION rate should be at 2 mmHg per second. State the BP to the patient both verbally and in writing.

The table shows follow-up schedules for the patients. Note that a normal BP would require follow-up only after 2 years and prehypertensives at 1 year! Since I started practice most patients I’ve encountered had an average BP measurement frequency of once a month!

Some situations would require ambulatory BP monitoring especially if you suspect the following:

  • Suspected white coat hypertension in patients with hypertension and no target organ damage
  • Apparent drug resistance (drug resistance)
  • Hypotensive symptoms with anti-hypertensive medications
  • Episodic hypertension
  • Autonomic dysfunction

Ambulatory BP monitoring would require admission for 24 hour BP measurement and evaluation. An automated cuff can be used so as not to rouse the patient while sleeping.

Self measurement can be done at home. JNC 7 indicates this particularly in smokers. However no guidelines as to how it can be conducted was ever written in the full version. On my practice, I follow a guideline I learned from a cardiologist. I ask the patient to monitor BP twice a day at the same time for 7 days and record the measurement irregardless of activity.


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