Wireless links enhance efficiency in medical apps - Embedded.com

Wireless links enhance efficiency in medical apps

Two recent events led me to write this article. I have written several times about field-programmable radio frequency (FPRF) devices that can become nearly universal wireless devices. I also had a two-week spell in hospital. This allowed me plenty of time to consider wireless applications on the hospital ward.

I soon realized that the nurses were being tasked with recording blood pressure, temperature, oxygen saturation, and heart rate at intervals of one, two, or four hours. This is called monitoring the vital signs. In practice, it involved scanning the patient's wrist band bar code, connecting (if not already connected) the device to the patient, and then recording the measurements by hand.

Here in the UK we have the National Health Service (NHS) which — as the name implies — spans the entire country. The newspaper headlines covering the application of technology to improve efficiency in the NHS tend to focus on major initiatives such as attempts to create a unified software environment. In this case, the objective is to link together larger general hospitals, regional centres of excellence, small local hospitals, and family doctor offices (known as general practitioners in the UK). However, within the NHS there is a good degree of local autonomy, and the hospital I attended had already embarked on a computerization scheme. This recorded drug use, but not the vital signs data, which was still hand-written into a paper record.

It struck me that if each patient had their vital signs read, say, six times a day taking ten minutes each time, then this took the nursing staff 60 minutes per day per patient. The addition of a simple wireless link could kick-start the automation.

So I wondered what were the problems preventing this happening? Proprietary instrumentation looks to be an obvious stumbling block. A range of major vendors produce the equipment and they may not think linking machines together is in their interest. Security is another paramount concern.

The particular machine that the hospital actually used was fitted with a data interface connector in the form of a 15-way D-type RS-232 serial port. However, in the cluttered environments of a hospital ward, the thought of connecting cables into wall sockets each time is a non-starter. On the other hand, it does seem to offer the possibility of attaching an external wireless communications module with a bar code scanner as a “second-best” option.

Implementing a wireless link
Modern wireless systems provide reliable links that could connect the hospital equipment to a local computer. Bluetooth low energy (BLE), which is marketed as Bluetooth Smart, is an example where there are existing profiles for certain medical applications. The first major limitation of BLE is the range, which extends to 100 meters (330 feet) in theory, but which may — inside a building — be limited to just a single room in practice. The second issue is the risk of interference in the spectrum that it uses — the crowded 2.4000 to 2.4835 GHz band.

However, to take full advantage of an integrated wireless system requires reliability over a longer range so that any readings can be sent directly to a central control at the nurses' station. This could involve passing signals through the walls of several intervening wards and still being detected 100-150 meters away (300-500 feet). A lower RF frequency, say below 1 GHz, offers a much better penetration of building materials. For this reason, the ISM bands of 915 MHz used in the Americas and 433.920 MHz in EMEA and other VHF/UHF frequencies used in Asia would provide a much superior range.

A newly released FPRF device promises to be an ideal solution for the wireless component of the problem. This chip (part number LMS7002M) is user-programmable over an extensive range, from 100 kHz to 3,800 MHz, so it easily covers the frequencies of interest. In addition to a programmable frequency, the user also has real-time control of the bandwidth and gain.

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