Page 36 - EE Times Europe Magazine | April2019

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Smartphone Sensor Gauges Blood Pressure with Clinical Accuracy

and diagnostic support on a server to store
the data. All three parts will comply with all
CE, FDA, and CFDA regulatory requirements
for a Class IIA/Class II medical device as well
as all relevant privacy regulations.
The V-Sensor has a pressure sensor embed-
ded in a soft, flat epoxy resin that is pressed
against the fingertip. LEDs and a photodiode
form a conventional pulse oximeter that
illuminates the tip of the finger. A thermopile
measures heat radiation to estimate body
Hardware setup (Image: Leman Micro Devices) temperature. The application-specific inte-
grated circuit designed by LMD controls the
happen during the day. According to proponents of the emerging tech- LEDs; captures and digitizes data from the photodiode, pressure sensor,
nologies, the continuous monitoring of biomedical parameters would and thermopile; and communicates with the mobile-phone processor.
encourage people to adopt and sustain healthy behaviors, with a view The V-Sensor can integrate into the back of a smartphone and is
to promoting health and preventing disease. curved to fit a fingertip. It offers a comfortable and ergonomic user
The solution offered by LMD uses innovative sensor technology to experience. To measure blood pressure, the user simply holds the
measure blood pressure, temperature, and pulse and even perform phone in a natural grip, with the index finger on the V-Sensor recessed
ECG functions, recording the electrical activity of the heart. The blood on the back of the phone and the thumb on the front screen. The
pressure measurement uses the Riva-Rocci procedure. e-Checkup app guides the user to play with the display by pressing
Blood pressure is the pressure exerted by the blood, pumped from harder or softer. A measurement takes approximately one minute. No
the heart, on the wall of the arteries that distribute blood in the body. external devices are required; an e-Checkup–enabled smartphone pro-
The blood pressure in the arteries can be measured directly by intro- vides the complete solution.
ducing a small tube (catheter) into the artery itself and connecting it to The app is the interface between
a measuring device (pressure transducer). In practice, this happens only the phone’s operating system and
in special circumstances, such as during surgery. LMD’s V-Sensor. It takes care of all
The common blood pressure measurement, on the other hand, is the processing, including obtaining
carried out indirectly, using special devices that are able to assess the the V-Sensor features from LMD’s
blood pressure from outside, in a non-invasive way. Of these devices, database the first time it is used.
the most precise and commonly used so far is the one designed by Blood pressure accuracy is within
Riva-Rocci just over a century ago. It consists of a rubber bracelet the scope of ISO 81060-2, which
connected on one side to a small hand pump and on the other to a for the main criterion is an average
mercury column pressure gauge. Because the instrument was equipped error of <5 mmHg and <8-mm stan-
with a glass column containing mercury and bearing a gauge indicating dard deviation.
the distance expressed in millimeters, the unit of measurement with All measurements can be taken
which the maximum and minimum blood pressure values are reported anywhere, anytime, in less than 60
is millimeters of mercury (mmHg). seconds by following the on-screen
Body temperature, meanwhile, is traditionally measured using an instructions and without the need
infrared forehead scan with environmental conditions, as first used for special accessories or prior
in 1835. ECG information can be obtained from a transducer placed calibration.
between the hands. Finally, traditional measurements of pulse rate, The sensor in question (a tiny,
blood oxygen (SpO ), and respiratory rate are all based on established 15-mm-long device to be placed
2
pulse oximetry transducers with established technology, in use since on the back of a smartphone) not
1972. Respiratory rate is derived from heart rate and amplitude modu- only allows you to measure blood
lation (respiratory sinus arrhythmia). pressure but, according to LMD,
“We have combined established, mature science with modern allows you to obtain accurate
technology,” said Chris Elliott, founder and director of Leman Micro measurements of body tempera-
Devices SA. “That gives users and their doctors measurements that Smartphone with V-sensor ture, oxygen saturation (a measure
they understand and know that they can trust with the convenience of (Image: Leman Micro Devices) of pulmonary function), heart rate,
a medical-grade device with them at all times. and breathing speed.
“For example, we measure blood pressure using exactly the same LMD’s research and development have shown that V-Sensor data can
science as a cuff around your arm, but we make it easier, smaller, and be combined with accelerometer data in the phone when held against
cheaper by using the fingertip and by getting the user to press harder or the chest to find the timing of the heart function: left ventricular
softer rather than having a heavy and expensive pump and cuff,” Elliott expulsion time (LVET), aortic and mitral valve timing, and many others.
added. Further measurements may combine images from the phone’s camera.
He explained that high blood pressure (hypertension) is a “silent A health economist developed a Markov model using empirical data
killer” with no symptoms, so putting a cuffless and calibration-free to estimate the health impact of buying a phone that measures blood
blood pressure meter into every phone could save the lives of many of pressure. He showed that, on average, a young user would gain about
the 9 million people who die from it every year. six months of life, while an older user would gain about three months
of life. ■
THE TECHNOLOGY
LMD’s technology consists of its V-Sensor hardware module and Maurizio Di Paolo Emilio is a staff correspondent at AspenCore,
e-Checkup software algorithm to instruct the user and analyze the data editor of Power Electronics News, and editor-in-chief of EEWeb.

APRIL 2020 | www.eetimes.eu