Medical Electronics
For remote patient monitoring systems, wireless coexistence can be lifesaving
By Naseef Mahmud, application development at Rohde & Schwarz T
he demand for wireless medical applications such as remote patient monitoring, real-time diagnostic analysis, smart surgical systems,
and implantable sensors have grown significantly over the last couple of years. Thanks to implanted medical devices, many patients live an almost normal life without having their mobility compromised. Popular implants include cardiac pacemakers, implantable defibrillators, nerve stimulators (functional electrical stimulation, FES), bladder stimulators, implantable infusion pumps, biomonitoring devices such as the capsule endoscope and implantable drug delivery systems. A patient’s quality of life is vastly improved by implants using wireless communication; the risk of inflammation and infection, often caused by connecting wires and tubes, is greatly reduced, as well as being much more convenient.
The wireless medical device segment that has seen the biggest jump in demand in recent years is remote patient monitoring. One of the biggest drivers of the soaring demand is most probably the pandemic and due to its nature, healthcare is invariably understaffed with the largest shortages in trained nurses and doctors. Wireless remote patient monitors (WRPM) can augment conventional electrical monitoring devices to help reduce direct contact with individual patients while a doctor can still monitor the vital conditions at all times. WRPM also enable a doctor to monitor multiple patients at the same time remotely, thus freeing up valuable time to attend to the needs of the patients who need immediate attention. Not to mention, WRPM give the patient far greater freedom of mobility by removing the danger of getting entangled with wires. Moving patients between locations while continuing monitoring is also a great deal easier.
18 December/January 2022
How do remote patient monitors transmit data? Typically, a wireless medical device utilizes both the 400 MHz MedRadio band and the 2.4 GHz MBAN band. The sensor data and control data are sent back and forth on different frequency bands. Increasingly, state-of-the- art patient medical devices are taking advantage of commercial standardized technologies such as WLAN, Bluetooth, Zigbee operating in the unlicensed ISM band. In certain applications, depending on the data rate requirements, where mobility is required, LTE or LPWAN (LORA & Sigfox) based implementations are also gaining popularity.
A WRPM gathers the patient’s vital signs data (such as body temperature, pulse rate, respiration rate and blood pressure) from wired measurement sensors and then wirelessly transfers the data via the Wi-Fi access point to the health care facility’s server system for storage at a central location. Medical personnel can then tap into the patient health status data by accessing it from the relevant server location using a networked connection. Figure 1 shows the intended WRPM architecture in a hospital environment.
Figure 1: Hospital operating architecture for wireless patient monitoring.
Future versions of WRPM systems will also support Bluetooth-based vital condition data gathering, which means that the sensors will communicate with the WRPM wirelessly and give the patient even more mobility and comfort.
RF spectrum and interference A WRPM is mostly used in a hospital. Nevertheless, there is a broad range of potential use cases that includes elderly care homes, military and defence applications and in some cases even at
Components in Electronics
a patient’s home. This means that the devices are subjected to very different environments for Radio Frequency (RF) transmissions. In many day-to-day environments, there is an abundance of wireless electronic gadgets, most of which also operate using licensed and un- licensed technologies such as Bluetooth, WLAN, cellular mobile radio, etc. Depending on the density of connected devices, the RF environment gets very noisy, particularly since the most data- hungry radio products operate in the ISM unlicensed bands; normally using the 2.4 GHz frequency band.
WRPM is exposed to a variety of RF environments depending not just on the application. If we consider just the hospital application use case, depending on the location of the hospital, the
RF environment differs quite a bit as well. A hospital in a big city usually sees more patients, and has more staff members and visitors than one in a rural location. In the big hospital in a city, more people bring in more mobile phones, smart watches, wireless car key fobs, Bluetooth headphones, and so on. All these devices transmit signals in the same frequency band at which the WRPM also operates. The microwave in the staff kitchen also radiates high levels of RF energy at 2.4 GHz. In addition, there is bound to be a high-powered LTE Base station tower nearby that could also act as an interference source for the WRPM and further complicate the coexistence challenge. Most hospital IT systems prefer to run regular system updates wirelessly in the night since
www.cieonline.co.uk
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66
