Oscillometric Method of Blood Pressure

The introduction of the oscillometric (wave) method to measure blood pressure using an automated device gave patients a way to check their blood pressure at home that was superior to earlier systems. Before this, the mercury-type method was too expensive for widespread home use and the aneroid system was cumbersome. Some important differences in the results from the three devices exist. However, with an understanding of the oscillometric method, these differences become less significant.

How It Works

• Automated oscillometric blood pressure measurement combines a recording device, an arm or wrist cuff, which inflates automatically, and a rubber tube connecting the two. When the cuff inflates, the pressure in the cuff eventually drops below the pressure exerted in the artery (systolic) by the beating of the heart. When the cuff starts to deflate, blood resumes flowing, causing the artery walls to vibrate. The cuff senses these vibrations and the blood pressure meter recognizes this as the systolic pressure. When the blood resumes normal flow, vibrations cease. However, it is not the absence of sound that signifies the diastolic (low point) as happens with the type of blood pressure in a doctor's office. Instead, a miniature computer in the meter performs a calculation that identifies the point at which the slope of the amplitude of the wave curve changes.

Factors to Consider

• Measurements on a specific individual will differ not only on the time of day but also depending on the type of meter used, according to reports in "Blood Pressure and Hypertension" and a study by Kaufmann et al. in "Anesthesia & Analgesia." Age and disease condition may cause other differences as well. Van Popele reports on arterial stiffness as a factor causing different readings in an oscillometric device and a sphygmomanometer in a doctor's office in an article in the journal "Hypertension."

  If a doctor has advised you to monitor your blood pressure at home, or just decide to do it for general health reasons, the most important step is take it to your doctor's office and calibrate the home meter against the doctor's readings. This may help prevent the doctor from getting a falsely high perception of true blood pressure, particularly if you suffer from the "white coat" syndrome, where blood pressure is artificially elevated in a medical setting. You may find the home device typically reads a bit higher by a specific percent, which you can factor into future readings. The artery mark on the cuff of oscillometric meter must be over the artery in the arm specified in the instructions for an accurate measurement. Always take measurements after resting for five minutes.

  Some oscillometric meters include pulse arrhythmia detection. This alerts the user to momentary irregularities in the heartbeat. A study in the "Journal of Human Hypertension" by G. S. Sturgiou, "Diagnostic accuracy of a home blood pressure monitor to detect atrial fibrillation", recommended the use as a screening test for atrial fibrillation, the most common arrhythmia.