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Automatic blood pressure devices are prone to significant errors,聽sometimes leading to the prescription of blood pressure-lowering medications to patients who don鈥檛 actually need them.

Now, researchers have developed a method to more accurately measure systolic blood pressure.

Based at the Jerusalem College of Technology and the Shaare Zedek Medical Center in Israel, the research team has developed a device 鈥� using a technique called photoplethysmography 鈥� that聽uses a pressure cuff wrapped around the arm and an electro-optic probe on the finger.

鈥淭he 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,鈥� Meir Nitzan, PhD, the new study鈥檚 first author,聽explained. 鈥淭he transmitted light exhibits pulses at the heart rate, due to cardiac-induced blood volume changes in the finger tissue.

鈥淲hen 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.鈥�

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 is usually assessed using either a manual (auscultatory) or automatic (oscillometry) meter in a doctor鈥檚 office or hospital. However, these measurements can be affected by 鈥榳hite coat syndrome鈥� 鈥� a patient鈥檚 fear or anxiety in a doctor鈥檚 office causing聽their blood pressure to measure above normal levels. To avoid the white coat effect, at-home automatic measurements taken by the patient may be required, but available oscillometry-based automatic meters offer a low level of accuracy.

鈥淭he automatic oscillometric technique is less accurate than the manual auscultatory technique, when both are used in the clinician鈥檚 office,鈥� Nitzan said. 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 an incorrect high blood pressure diagnosis may be prescribed blood pressure-lowering medication unnecessarily. These medications can cause patients鈥� blood pressure to dip too low (hypotension); elderly patients are especially at risk. 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.

Nitzan recently presented his findings at an American Physiological Society conference,聽Cardiovascular Aging: New Frontiers聽and Old Friends聽conference, in Colorado, USA.

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