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Scientists devise better way to measure BP

Currently available automatic blood pressure measurement devices are commonly off by 10 to 15 mmHg. This is mainly due to indirect determination of the blood pressure from the oscillometric air-pressure wave measurements taken by automatic devices.

A patient with  incorrect high blood pressure diagnosis may be prescribed blood pressure-lowering medication unnecessarily. These medications can cause blood pressure to dip too low (hypotension).

Side effects of hypotension can include short-term symptoms such as dizziness and fainting and long-term problems such as insufficient blood supply to vital organs, which can lead to acute kidney injury and cognitive impairment.

A research team has developed a device — using a technique called photoplethysmography — to more accurately measure systolic blood pressure. The device uses a pressure cuff wrapped around the arm and an electro-optic probe on the finger.  “The finger probe is similar to that of pulse oximeter: It includes a light-source emitting light into the finger and a detector, which measures the light transmitted through the finger,” Meir Nitzan explained.

“The transmitted light exhibits pulses at the heart rate, due to cardiac-induced blood volume changes in the finger tissue. When the cuff pressure increases to above systolic blood pressure these pulses disappear, and when the cuff pressure decreases to below systolic blood pressure they reappear. This effect enables the determination of systolic blood pressure.”

A systolic blood pressure measurement of 140 mmHg or higher and a diastolic measurement of 90 mmHG or higher (140/90 mmHg) is considered high.

Blood pressure  measurements can be affected by “white coat syndrome” – fear or anxiety in a doctor’s office causes blood pressure to measure above normal levels.


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