Proving the Business Case for the Internet of Things

Maxim reference design allows cuffless blood-pressure monitoring

Steve Rogerson
December 3, 2019



California electronics company Maxim Integrated has unveiled a cuffless blood-pressure measurement device that meets Class-II regulatory accuracy limits. The reference design enables optical blood-pressure monitoring without requiring bulky, expensive mechanical cuffs.
 
Until now, accurate blood-pressure monitoring could only be achieved with bulky and mechanical cuff-based medical devices. Now, Maxim has introduced a solid-state blood-pressure monitor to track this critical health indicator more conveniently.
 
Design engineers can develop blood-pressure trending products with the Max Refdes 220# reference design. Comprised of an integrated optical sensor module, a microcontroller sensor hub and a sensing algorithm, the design can be embedded into smartphones or wearables. It lets users place their finger on a device for 30 to 45 seconds while resting to measure blood pressure anywhere and anytime.
 
The reference design includes the Max 30101 or 30102 high-sensitivity optical sensors, as well as the Max 32664D sensor hub IC with built-in algorithms.
 
The Max 30101 using three LEDs and 30102 using two LEDs pulse-oximeter and heart-rate optical sensor modules combine photodetectors, LEDs and analogue front-end electronics with an integrated cover glass. This integrated optical design and lenses-on-top approach enables optimal signal-to-noise ratio for a small, lower cost and power-efficient module.
 
It comes in a 5.6 by 3.3mm 14-pin optical package with an I2C interface to the sensor hub IC.
 
The Max 32664D sensor hub IC includes firmware that controls the sensor and executes the algorithms that measure cuffless blood pressure, heart rate and blood-oxygen levels. Its 1.6 by 1.6mm size can easily fit into small devices to connect to a device’s host microcontroller seamlessly and effortlessly.
 
The reference design meets Class-II regulatory limits. For example, under resting-only measurement conditions, it provides the following accuracies:

  • Systolic error: Mean = 1.7mmHg, standard deviation = 7.4mm Hg
  • Diastolic error: Mean = 0.1mmHg, standard deviation = 7.6mm Hg
  • For reference: Class-II regulatory limits are mean error ≤ 5mm Hg, and standard deviation ≤ 8mm Hg
This requires calibration every four weeks to maintain the above accuracies. This is based on independent testing and a limited number of subjects at resting condition.
 
The algorithm code runs on a small, low-power dedicated sensor hub microcontroller, eliminating the need to integrate new code into an existing application processor.
 
“Blood pressure is a key vital sign, but has traditionally been difficult to monitor conveniently and accurately,” said Kris Ardis, executive director at Maxim Integrated. “Maxim now provides a combination of products in a compact reference design which allows system designers to build highly accurate – and based on our patient testing, the most accurate – blood-pressure monitors that do not require cuffs.”