欧州麻酔科学会

ESA Poster：English(英語版)

Japanese(日本語版)

The interference of electrical appliances with SCS and the effectiveness of shielding clothing for the patient with SCS

Yoko Kume, M.D.*, Hiroshi Igarashi, M.D. *, Motoya Matsumoto †,Hideki Matsui ¶, Shigehito Sato, M.D.

Department of Anesthesiology and Intensive Care, Hamamatsu University School of Medicine, Hamamatsu, Japan,†Technology Research Institute of Osaka Prefecture, and ¶Medical-Aid co. Ltd.

Background and Goals

Spinal cord stimulation system (SCS) is widely used for the patients with chronic pain. Recently electrical appliances which make strong magnetic field, such as an induction heating (IH) cooking plate, have been widely used. In spite of many reports of electrical interference in pace-maker (PM), no report has been described about the SCS. We investigated electromagnetic interference of IH cooking plate to SCS

Case

A 59-yr-old female. She has had vasospastic angina　since 48 years old.SCS therapy was started when she was 53 years old.When she was 59 years old, she bought an IH cooking plate. Every time she was cooking with the cooking plate, she felt discomfort in her neck and back.She explained the feeling was very uncomfortable therefore she couldn’t stand the feeling. The feeling disappeared when she was moved 2 meters away fromthe cooking plate.

Material and Methods

For investigating electromagnetic interference of IH to SCS, we did the following two examinations.

Experiment 1.

We assessed electromagnetic interference of IH cooking plate to SCS in a human body model and the shielding effectiveness of shielding clothing by using oscilloscope.The human body model we used was a human body shaped midair container made of resin filled with 0.18wt% NaCl water solution, which is simulating electricity constant of the human body (Irnich’s model 1) ) (Fig.1). We put a SCS system into the human body model, exactly the same position as we used in the patient.We examined the waves on an oscilloscope when we brought the IH cooking plate (1350W) close to SCS in the human body model with and without shielding clothing covering SCS (Fig.2).The shielding clothing we used was for the patients with PM which is commercially available in Japan .

Fig. 1: A human body model

Fig. 2 A: human body with shielding clothing covering SCS.

Fig. 2 B: human body without shielding clothing covering SCS.

Fig. 2: We examined the waves on an oscilloscope when we bought the IH cooking plate close to SCS in the human body model.

Experiment 2.

The study was approved by the Hospital Ethics Committee, and written informed consent was obtained from the patient before examination.The patient used 3 types of shielding clothing; (1) shielding clothing for the patients with Pace Maker (PM) which is commercially available in Japan, (2)(3) 2 types of shielding clothing improved and updated (Fig.3).The patient stood in three different positions; standing straight (Fig.4-A) , leaning forward with her chest covering the IH cooking plate (Fig.4-B) and standing backwards (Fig.4-C).We set the appliance at the highest power (1350W).We observed her symptoms for 10 minutes, but stopped if the symptoms appeared.

Fig.3　Shielding clothing 〇: position of generator, : position of shields.

A: Shielding clothing for the patients with Pace Maker (PM) which is commercially available in Japan.

B: Improved clothing with a long shield covering her chest, left shoulder and left side of her back.

C: Improved clothing with two separate shields, one was covering her chest and another was covering the left side of her back.

Fig.4: The patient stood in three different positions

A: standing straight

B: leaning forward with her chest covering the IH cooking plate

CC: standing backwards

Result1

When we put the IH cooking plate close to SCS in the human body model, small noise waves appeared on the oscilloscope.We examined the waves in detail changing the scale of oscilloscope, and we found that there were small waves of various frequencies on big waves. The maximum voltage was 22mV.The frequencies of big waves were about 60 Hz, the frequency of AC electric supplied in this area.With shielding clothing covering SCS in the human body model, the wave on the oscilloscope did not occur.

Result2

Table1: the effect of shielding clothing to prevent symptom of the patient.
*: discomfort in her chest, **: an compressive feeling on her left shoulder , ***: no symptoms

Discussion

Fig. 5: radiograph of the patient. Lead wire makes coils (in squares) inside her body.

In experiment 1, we observed IH cooking plate inducted an induced current with an SCS system. IH cooking plate did not turn the SCS switch neither on nor off. We supposed that the patient felt discomfort because the induced current of SCS induced by IH cooking plate stimulated patient’s spinal cord.In order to prevent this phenomenon, we thought we should cover the coils of lead wire of SCS system with some shielding devices.In experiment 2, the shielding clothing for PM was not effective enough to prevent this phenomenon. So, we changed the shield to a longer one which covered both her left chest and her back where the two coiled parts of SCS lead were implanted (Fig.5).

This shielding clothing was not effective enough neither. We thought, with this long shield, electromagnetic field was not blocked but induced toward her backward.we improved the clothing again with two separate shields. Using this clothing she didn’t complain any symptoms.We are going to examine the effectiveness of the shielding clothing for another patients with SCS.

Conclusions

IH cooking plate gives electromagnetic interference with SCS not in the generator but at the part of coiled electrode.Appropriate shielding clothing can prevent the interference, patient’s discomfort and can protect patient’s safety.

References

1) Irnich, W.: Interference in pacemakers. Pacing Clin Electrophysiol. 1984 Nov;7(6 Pt 1):1021-48