The use of connected medical devices or medical equipment in hospitals has increased with the expansion of wireless technologies and advancement in medical device designs. As a result, the number of connected devices in a large hospital or a healthcare facility reaches 85,000 at any given time1. As the density of the connected devices increase, so does the density of the electromagnetic environment; and there are concerns about the impact from sources producing radio frequency interference (RFI). Advances of technology in medical devices and many general consumer products are significantly affecting the efforts aimed at maintaining the required operations and interoperability between the products in a hospital or healthcare facility.
Some of the RFI sources in a hospital environment are, natural or ambient electromagnetic energy like lightning, television transmission or AM, FM or satellite radio. Other sources are from medical equipment and consumer products like ventilators, cardiac defibrillators, infusion pumps, motorized wheelchair, MRI systems, cellphone, tablet or laptops. RFI can cause many serious problems, some of which can lead to a patient’s death. There have been many reported cases; sleep-apnea monitors failed to sound an alarm when babies stopped breathing, power wheelchairs started rolling after their brakes released because of certain field strengths, and anesthetic gas monitors stopped working when influenced by interference from electrosurgery units2.
Hospital administrative staff, product makers, patients and the public has a huge responsibility and challenge to keep pace with efforts needed to maintain the required level of electromagnetic compatibility (EMC) in a hospital environment. Here are some examples of how everyone can play their part.
Hospital administrative control:
1. RF shielding
There are two reasons why certain medical equipment needs to be shielded. As an example, let’s take an MRI machine. The MRI machine is usually placed in a shielded room to prevent extraneous electromagnetic radiation from distorting the MR signal, and secondly, to prevent electromagnetic radiation generated by the MR scanner from causing interference to nearby medical devices. RF shielding must encircle the entire room; walls, ceiling and floor. The management of hospital could also consider less expensive materials that can increase shielding capacity, such as electricity-conductive paint, electricity-conductive wallpaper, and electricity-conductive cloth for less critical areas in the hospital.
2. Restrict RF sources from certain areas in the hospital
Controlling the number of devices that could potentially contribute to the radio frequency interference (RFI) in a specific area will help to lower the risk of interfering operations of clinical and other electronic equipment. The management of hospitals should take measures to control the electromagnetic environment in the hospital by restricting cell phones and other potential RF sources from sensitive areas in the hospital; such as the intensive care unit, the neonatal intensive care unit and the operating theater, where critical care medical equipment is in use.
Public and patients:
3. Implementation of control techniques
There has been an increase in the use of electronically controlled medical devices outside the clinical environment, and they are often used at home, attached or implanted into a patient. RFI problems will also affect these patients, especially patients with cardiac pacemaker implants. Though the chances of an EMI from a cellphone could produce a life-threatening situation, certain steps are advisable to minimize any risks. Government bodies has issued caution and recommendations to the wearer3.
- Using a cellphone very close to the pacemaker may cause the pacemaker to malfunction.
- It is advisable to avoid carrying a cellphone in the breast pocket directly over the pacemaker because an incoming call will switch the phone to its transmission mode and may cause interference.
- When using a cellphone, it is advisable to hold it to the ear farthest from the pacemaker.
Medical device makers/developers:
4. RF immunity of medical devices
For many years now, military, aircraft and automotive electronic systems have been required to meet strict RFI immunity requirements. The technology has been developed and can be easily deployed for medical devices. Most techniques are not costly if they are incorporated into the electronics system design in the early stage. The international standard for RF immunity of medical devices is the IEC standard 60601-1-2, requires a minimum immunity level of 3 V/m in the 26-1000 MHz frequency range4. Medical device developers and makers need to consider incorporating RF immunity techniques like shielding, grounding and filtering to ensure the medical devices are in conformance with the standard and is robust against RFI.
5. Incorporate RFI immunity into product design
Modern medical devices are getting smaller in size; combining low power integrated circuitry which is more sensitive and susceptible to RFI. A medical device maker could incorporate RFI immunity into the product design, making sure the medical device is robust and able to work well above the defined minimum immunity level. One way this could be done is by testing the product in a real-world setting to ensure the medical device is able to withstand high RF field strength.
As you can see, there are many ways to deal with electromagnetic interference in a healthcare facility. However, the field strength to which the medical device may be exposed to depends on many conditions, and is beyond what the medical device makers or developers can do. It is up to the hospital administrative staff to impose and regulate a certain guideline to maintain safe environment for the hospital patients.
Here is a related webinar that talks about RF Coexistence challenges, what is RF coexistence testing and how it is performed. And if you are looking for solutions to combat your design challenges, please go to www.keysight.com/find/IoT for more information.