Electro-medical equipment protection

From an average of four devices per bed in the early 1980s today the level has reached close to fifteen devices per bed. A four fold plus growth recorded in about a quarter century. The trend is still growing and will keep on growing in future. However in comparison the Bangladesh hospital scenario particularly in the ICU and CCU levels may possibly average around four electro medical devices per bed; possibly reflecting our development level in the sector.

Along with the benefits that these devices provide; they bring new areas of problems and issues that needs to be addressed. With more electro medical devices in use, there is greater possibility of electro magnetic interferences (EMI). These are invisible waves and pulses that move through space, interfering with the electrical and emission function of the devices. EMI problems usually tend to be difficult to identify, and are generally transient in nature. Both the utility power supply as well as the hospital facility electrics can be the cause of EMI related problems. Some of the common potential sources causing EMI problems among others are the following:

-- Radio transmitters, paging units, walkie-talkie units used by personal in hospitals.
-- Television receivers and equipment video monitors.
-- Analog and digital cellular and wireless telephone.
-- Microprocessor based patient monitoring devices like electrocardiographs, BP monitors, hypothermic machines and security detectors.
-- Radiating equipments like fixed and mobile x-ray and electro surgery equipment.

Some of the EMI problems encountered in USA are summarized below. Unfortunately there is no corresponding record or report of such events in Bangladesh as our awareness on the subject is not widespread. In this matter unfortunately this particular electrical disease of equipments has neither been diagnosed nor treated in Bangladesh hospitals. Some example of US experiences are provided here to serve as reference and guide:

-- Anesthetic gas monitor displaying error in gas concentration readings during surgery. It was subsequently revealed that the culprit was the electronic knife used during surgery.

Radio-wave interference which caused malfunction of breathing monitor alarms, even from cellular phones when used close by.

-- High frequency "noise" or interference from electronic equipment within the hospital disrupting the hospital appointment clock setting.

-- CT Seamier failure occurring during the time when capacitors where switch on at the hospital incoming power switchgear. The switching caused an oscillatory transient affecting the CTS scanner.

These and many other power quality issues have an important impact on the reliability and diagnosis provided by a clinic or hospital. Quite often; unknown to us we inadvertently blame the physicians for giving wrong diagnosis which is the result of their interpretation of faulty images or signals directly or indirectly caused by the quality of electrical power supplied and electrical interferences. Hospitals in Thailand and Singapore are aware of these issues and hence we often see that their diagnosis is different from ours, not because of our physician's mistake in interpretation of data; but due to deficiency in electrical power quality and protective measures that are usually absent resulting in data errors.

This writer had the opportunity to go round a CT, X-Ray and Radio Imaging section of a hospital in Bangkok. He was shown the protective and corrective electrical and electronic devices installed; and was told that the cost of the protecting and power filtering devices represented over forty percent of the cost of the total set up of the electro medical equipments.

This is a somewhat new area for our growing electro medical facilities, which directly affects the reliability of the outputs from electro magnetic diagnostic equipment, due to its high sensitivity to the quality of power available. This is beyond voltage fluctuation, high and low voltage surges and flickers which are normally noticeable and visible even to the eye. I believe that this awareness and the solutions to overcome it should be available at our hospitals and clinics and the physicians and relevant staff involved in the use of these facilities are provided required knowledge on the subject. This will result in better performance of medical diagnosis by our physicians, and avoid many problems unnecessarily caused by unknown external factors.

The writer is Director, Engineering, Partex Group.