Advanced Medical Monitoring: High Performance, Low Power

This ring-based smart pulse oximeter provides continuous key health data such as blood oxygen and heart rate updates with great battery life. Nordic’s nRF52832 SoC makes it possible.

In the growing market of smart healthcare, one Chinese company is ringing the changes.

MegaHealth has launched a Smart Pulse Oximeter in the form of a ring. With Bluetooth Low Energy connectivity and MegaHealth’s Medical Pulse Oximeter, patients can access blood oxygen and heart rate updates day and night from an app.

The ZG-P11D Medical Pulse Oximeter has passed trials in the country’s National Medical Products Administration and is now being widely adopted by hospitals in China.

The new device is small, comfortable and more suited to long periods of wear than the clip-based alternative. But don’t get the wrong idea; small still means powerful. The performance of the Nordic nRF52832 SoC provides continuous synchronisation of oxygen saturation and pulse rate data over a Bluetooth low energy connection to the user’s smartphone. Yet that’s combined with optimised power consumption that allows the ring to run for more than 20 hours before recharge, which is done using the common Micro USB connector.

What is a pulse oximeter?

If you’ve ever had a stay in hospital, or visited relatives or friends, then you’ve almost certainly seen a pulse oximeter. Usually it’s a clip that stays on one of the patient’s fingers and it measures oxygen saturation in the blood.

The pulse oximeter works by measuring the difference in absorption of red and infra-red light. Deoxygenated blood absorbs more red light than infrared and oxygenated blood absorbs more infrared light than red light. These principles have been known since the first half of the 20th century. The familiar clip-on device that’s in use worldwide today has been around since the 1970s.

Why oxygen saturation is important

Our bodies need oxygen to function. The amount of oxygen in our blood can be an indicator of various problems. Oxygen saturation is an important metric in many conditions including Pneumonia, Asthma, COPD and Heart Failure.

Unless you’re in the middle of a punishing gym workout, oxygen saturation – the percentage of haemoglobin in the blood that is carrying oxygen – should be around 98%. A low reading of 94% or lower at rest means something is wrong. Either the lungs aren’t working effectively, or the body is using more oxygen than it should be.

Consumer monitoring

Outside of a hospital setting, oxygen saturation measurements can be useful too. A condition such as sleep apnea, where people stop breathing for extended periods during sleep, can be detected without the need for a full sleep study. It can also provide monitoring of conditions such as asthma to check how they’re responding to treatment without the need to take up a hospital bed.

Measurements can be useful to consumers in terms of improving fitness. Oxygen levels can tell wearers how efficiently the body is using oxygen during exercise and how quickly it is recovering afterwards.

Smart watches from companies such as Garmin and Withings already provide Pulse Oximetry as one of their key metrics. Runners can see whether their underlying fitness is improving and take steps to vary their workouts for further gains in pace and endurance.

Nordic at its heart

The new device from MegaHealth is a triumph of engineering. The ring is small, waterproof and comfortable for long periods of wear. As a ring, it’s more secure than a finger clip and so won’t fall off during sleep.

Yet its small form factor manages to pack in a lot of power. The Nordic nRF52832 SoC acts as the core microcontroller with its powerful 64MHz, 32-bit Arm® Cortex® M4F processor. The 512kB Flash memory is sufficient to store and record the data, while the 64kB RAM is enough for the algorithm filtering requirements.

According to MegaHealth’s Jan Wang, the Nordic nRF52832 SoC “superbly balances” power consumption and real-time performance.

Thanks to the optimised energy use, the bespoke lithium-ion battery can last more than 20 hours in continuous use before recharge. As a wireless device, monitoring can continue when a patient leaves a hospital bed to walk around, for example. This is often a crucial time for oxygen saturation monitoring that is missed in traditional wired systems.

A healthy marketplace

MegaHealth and other companies continue to look into producing novel products that can add value in both hospital and consumer settings. Whether it’s monitoring heart rhythms to provide early warning of serious conditions or monitoring existing conditions in ways that weren’t previously possible, the market is set to expand for some time.

Personal health monitoring is one of the biggest growth areas for smart technology. There is still plenty of potential for devices that provide more data for health-conscious consumers is still huge. And with today’s powerful, low-power chipsets from Nordic, the ability for manufacturers to offer more functionality is ever increasing.

This article was first published on Nordic's Get Connected Blog.