Letter to the Editor

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LETTERS

TO

THE

EDITOR

This column has been established to provide a forum of all niembers of the profession for

exchange of information and views. Statements and opinions expressed in ktters are those of the authors and do not represent the official position of the American Academy of Pediatrics, Inc.,

or its Committees.

Comments on the contents of PEDIATRICS, or any topic of general interest are invited. Letters should be in double-spaced typing on standard bond paper. Those accepted will not be subject to alteration, except as to proper form. The Editor reserves the right to publish replies to letters and to solicit responses from others. Address inquiries for reprints to PEDIATRICS, P.O. Box 1034, Evanston, Illinois 60204.

Grounding and Electrical Leakage of Photo Therapy Equipment

To Tsiu EDITOR:

I am the director of the Bio Electronics Lab

at Wilson Memorial Hospital. We have a

safety program in which electrical leakage on

all electrical and electronic equipment is

checked. Our standards are set in accordance

to the American Heart Association at 5 micro-amps. This brings me to the purpose of this let-ter.

We received an Air Shields photo therapy unit which is used in the prevention and

treat-ment of neonatal hyperbilirubinemia. This

lamp has a leakage of 70 micro-amps when it

is ungrounded. Many nurseries are not

equipped with proper grounded outlets, and

the unit then becomes potentially dangerous. Many authorsl2 stress the danger of “micro-ampere electrocution” in adults as being in the

range of 10 to 20 micro-amperes. I dare say

that a newborn infant can be hurt by a lesser amount of leakage current. The Air Shields

Company was informed of my findings, and I

have a letter from them confirming the leakage. I feel that your readers should be warned of the danger and take precautions to see that the unit is properly grounded through a three-wire line cord and not through an adapter which Air Shields (to their credit) stopped shipping with the units. The leakage can be measured with a commercially available leakage detectors and should be measured from ground of the electri-cal outlet to any exposed bare metal portion of

the unit. It should not, under any

circum-stances, exceed 1.5 micro-amps, as we are

dealing with newborn infants. Our unit

mea-sured 34 micro-amp when it was properly

grounded. Incidentally, we shipped our unit back to Air Shields as we cannot accept any unit in this hospital with over 5 micro-amperes ungrounded. I hope that this information will be of value to you and your readers.

BERNARD Si-iuN, DIRECTOR

Bio-Electronics Laboratory

C. S. Wilson Memorial Hospital Johnson Cit,’, New York 13790

REFERENCES

1. Bruner, J. M. R. : Hazards of electrical

appara-tus. Anesthesiology, 28, March-April, 1967.

2. Whalen, R. E., and Starmer, C. F. : Electric shock hazards in clinical cardiology. Modem Conc. Cardio. Dis., 36, February, 1967.

3. Camsafe. Cambridge Instrument Company, Os-sining, New York.

EDITOR’S NOTE: The following comments have been obtained from (I) Dr. Lucey and

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)

Dr. Toolev:

(I) In response to Mr. Stein’s letter to

PEDI-ATRICS I asked several manufacturers of

photo-therapy equipment for their comments and opin-ions on the present status of their equipment. The following are excerpts from their replies.

MR. C. B. ANDREASEN, AIR-SHIELDS, INC., HATBORO, PENNSYLVANIA

As you are aware, the subject of safety in hospitals is receiving a great deal of attention these days; and, a number of well respected groups, including NEMA (National Electrical Manufacturers Association ), AAMI

(Associa-tion for the Advancement of Medical Instrumen-tation ), and UL have organized committees

to recommend safety standards for electrical

equipment. We have been following the

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LETTERS TO THE EDITOR 615 until the time of the recent UL proposal, the

consensus had seemed to be that equipment in

direct contact with the heart should not exceed

5 to 10 micro-amps leakage, equipment with

surface electrodes should not exceed 100

mi-cr0-amps, and all other equipment should not

exceed 500 micro-amps. Based on this

pro-posal, which defines “electrically sensitive”

areas, all equipment used in an intensive care

nursery would be required to comply with a 5

micro-amp maximum leakage. I can agree

com-pletely in principle with the objectives of such requirements, but I’m not certain that it

repre-sents the most practical approach to providing

maximum patient safety. There appears to be a threefold responsibility in dealing with the question of patient safety which would require the hospital to provide a safe, foolproof,

grounded wiring system and the operating

per-sonnel to be properly educated in the use and potential hazards of electrical equipment, and the manufacturer to provide safe, foolproof equipment to be used in conjunction with ap-proved wiring systems. To place the burden of safety entirely on the equipment manufacturer

regardless of the adequacy of hospital power

and/or personnel training may be unrealistic. We are, at the present time, assessing the fin-plications and practicality of implementing

such leakage standards should they be adopted and are investigating other methods to provide added safety in the use and abuse of electrical

equipment. It would be safe to say at this

point that very little of the equipment now in

use in hospitals would conform to these specifi-cations.

Concerning the potential hazard of the

Pho-totherapy Unit, we are confident that no haz-ard exists if operated as designed, i.e., properly grounded. Even if left ungrounded, the hazard

seems extremely remote. In addition to the equipment being ungrounded, it would be

nec-essary for a grounded intro-cardiac electrode

be in place and that some contact be made

between the patient and the unit. We heartily

endorse Mr. Stein’s recommendation that the

units be used properly grounded, but I fear the

hazards are perhaps distorted somewhat out of proportion.

MR. JAY JONES,

OLYMPIC SURGICAL COMPANY, INC.,

1117 SECOND AVENUE, SEATTLE, WASHINGTON

After receipt of your inquiry regarding pos-sible electric leakage in the Olympic Bili-Lite,

we turned over a production model of the

Bili-Lite to Professor Arthur Guy at the Uni-versity of Washington School of Medicine for

testing. Dr. Guy is an electrical engineer work-ing in the biomedical field and has done pre-vious research in the subject of hazardous elec-trical leakage and electro-magnetic radiation from equipment.

I am enclosing a copy of Dr. Guy’s letter

re-porting his findings in regard to the Olympic

Bili-Lite. I would also like to make some

addi-tional comments on this subject from our point

of view, as a manufacturer.

Our lamp does have a three-wire ground

cord; and, if it is properly connected to a

three-wire ground receptacle in the nursery,

there is no danger from normal shock hazards.

Nursery personnel should not use any type of

adaptor or connector between the lamp and

the floor receptacle which interrupts the

ground connection. This is true, of course, with

any piece of equipment, incubators, and so forth that have three-wire ground cords; they

must always be properly grounded to a three-wire outlet.

In regard to the possible danger to newborn infants from stray electrical leakage from the Bili-Lite, as Professor Guy has pointed out, this is a complex subject and one that cannot be answered with a simple statement to the ef-feet that a piece of equipment has a leakage of

so many milliamps. We are dealing here with

minute voltages that, for the most part, appear to be induced by stray electromagnetic radia-tion in the nursery. These microvoltages will

vary considerably from place to place on the

equipment and, depending upon the ground

reference source, also the magnitude of the current flow will, obviously, depend on the re-sistance in the ground path. Because of the

many factors involved, it would seem that, to

accurately establish the danger to a newborn

infant from electrical equipment, it would be necessary to evaluate that equipment in rela-tion to the total electrical environment of the

nursery.

It is our belief that, with the normal use of

our phototherapy lamp, there would be

vir-tually no danger to the infant. In the first

place, the lamp does not normally come in

contact with or touch the infant, incubator, or bassinet. Actually, since the incubator itself is

also a piece of electrical equipment, it would

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electrical circuit of a lamp placed over the in-cubator than from the incubator itself.

Furthermore, it is difficult to understand

how a difference in potential would develop across the infant’s body, even under the

cir-cumstances of leakage in the incubator, since

the l)aby is not usually grounded. On the other

hand, there is the situation where the baby might have a cardiac monitor or another lead

attached, which would provide a ground path,

and, therefore, create a hazard.

DR. A. W. GUY, ASSISTANT PROFESSOR, DEPARTMENT OF PHYSICAL MEDICINE,

UNIVERSITY OF WASHINGTON, SEATTLE, WASHINGTON

Regarding your letter of April 15, 1969, we evaluated the potential dangers of your pho-totherapy lamp in our laboratory. The potential difference between the metal frame of the

en-ergized lamp and the receptacle ground was

found to be 1 to 2 millivolts R.M.S. (depend-ing on lamp orientation in the room

)

. The

measurement was done with a Hewlett Pack-ard 400 E/EL AC voltmeter.

A 20-gauge wire was then connected

be-tween the lamp frame and the electrical outlet ground. A current of 120 to 240 micro-amperes

was measured through this wire by means of a

Hewlett Packard 456 AC current probe and

the 400 E/EL voltmeter combination. It

ap-pears that these results could be expected from induced voltages and currents due to normal magnetic coupling between the power circuits in the room and the lamp frame and wiring.

Under these same conditions, a human

sub-ject grounded at the outlet potential coming in

contact with the lamp frame would be exposed to no more than 2 micro-amperes of current ( assuming a minimum resistance path of 1,000

ohms through the subject’s body) . Thus, it

appears that the lamp would satisfy the criteria discussed in the attachment to your letter,

pro-vided the third ground wire of the lamp is

properly connected to the electrical outlet box and the subjects exposed to the lamp are at the same potential as the outlet ground.

I should point out, however, the results dis-cussed here are unique to the particular room where the test was made and in no way infer that the lamp could safely be brought in con-tact with a subject when the subject is in con-tact with other electrical equipment that is

im-properly grounded or grounded to another

reference point. Situations could also arise

where magnetic field coupling between the

ad-jacent power sources and the lamp could in-duce dangerous currents. However, these

prob-lems should be eliminated by the agency using

the lamp through proper grounding and

shielding of associated equipment and wiring.

We were happy to make this evaluation,

both from the standpoint of acquainting our-selves more with this important problem and

also to contribute our services in the interest of

1ublic safety.

MR. HOWARD DRESCHLER, NATIONAL BIOLOGICAL CORPORATION,

6057 MAYFIELD ROAD, CLEVELAND, OHIO

When our unit

(

Bilirubin Reduction Lamp)

is ungrounded, there is a leakage of .061

milli-amps. Grounded, there is no leakage. All units are shipped with a three-pronged plug.

As soon as the formal statement of the inde-pendent testing lab is available, we will

for-ward it to you. General Electric Company is

also testing.

MR. MIGUEL MENDOZA, ROWAN INDUSTRIES, OCEANPORT, NEW JERSEY

All our units are grounded through a

three-wire line cord and three-pronged plug so, there

can be no leakage present that could be

dan-gerous to the nurses or infants.

This unit cannot be plugged into anything

but a UL approved grounded socket. In this

way it is impossible for the unit to be used

in-correctly.

Dr. William Tooley, a member of the

Com-mittee on Fetus and Newborn of the American Academy of Pediatrics, has been interested in the problem of electrical hazards in the nursery for some time and he was asked to comment on the overall general problem. His letter fol-lows. This is a new area of concern in the

nur-sery. As many have pointed out it is not a

sim-pie matter to which a simple answer can be

given. The Committee on Fetus and Newborn

intends to look into this area and will try to make

practical suggestions in the near future.

J

EROLD F. LUCEY, M.D. Coichester Avenue

Burlington, Vermont 05401

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LETTERS TO THE EDITOR 617

A current of 100 to 200 milliamperes

ap-plied to the skin is required to produce

fibrilla-tiOll ill the adult because resistance to current

flo\v iS large. However, only 200

micro-am-eres may produce fibrillation if it is

intro-duced directly into the heart by means of an

intracardiac catheter or pacemaker. No one

knows the amount of current which will cause

fibrillation in the newborn infant; but, as pointed out by Mr. Stein, it must be much less

than these figures for the adult. The

introduc-tion of catheters through the umbilical vein

into the inferior vena cava or right heart and through the umbilical artery into the

descend-ing aorta greatly increases the hazard to the newborn infant. The C. S. Wilson Memorial Hospital has set rigid standards which equip-ment must meet before it is acceptable for use

in the nursery. It must be emphasized that

what they have found with the Air Shields’

phototherapy unit may occur in other pieces of

equipment used in the nursery. At one time or

another, apnea alarms, oscilloscopes, ECG ma-chines, direct-writing recorders, portable sue-tion devices, incubators, heated nebulizers, and

heat lamps have been inadequately grounded

and have had excessive current leakage. In

other words, almost all of the electrical

appara-his which is used in the nursery can be

hazard-oils.

Since

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1

)

the exact amount of current

leak-age which is safe is unknown, (2) small

amounts of current are probably more

danger-oils to the infant than to the adult, particularly

when indwelling umbilical catheters are used,

and

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3

)

increasing numbers of complex electri-cal equipment are being used in the nursery, the following precautions should be taken:

1. Electrical outlets in a nursery should have

a common ground. There should be sufficient

outlets, all to a common ground, at each bed

sta-tion to handle all the different pieces of equip-ment needed for one infant. Adaptors, extension cords, and junction boxes should not be used.

2. Electrical apparatus must be checked for current leakage before use and after it is

corn-l)med with other e(luipmeflt for the care of one

pttient. The Seal of Approval of the

Underwrit-ers Laboratory is not adequate; the

Underwrit-ers accept any piece of apparatus which has

current leakage of no more than 5 milliamperes ( 5,000 micro-amperes

)

through a resistance of 1,500 ohms to ground.

3. At least once a month all electrical

equip-ment used in the nursery should be rechecked

for physical grounding of wires and current

leakage.

4. Nurser personnel should be thoroughly instructed in the potential electrical hazards

ex-isting within the nursery.

5. Complexities encountered in

environmen-tal control and monitoring justify the

employ-ment of a hospital environmental and safety

engineer who should ensure the efficacy and safety of electrical equipment at all times.

WILLIAM H. TOOLEY, M.D.

University of California Medical Center

San Francisco, California 99122

The Pediatric Convalescence Hospital (Continued)

To TIlE EDITOR:

I was delighted to read Dr. Frederic

Burke’s excellent analysis of the important and

unique role of the specialized children’s

hospi-tal designed to meet the complex needs of

long-term childhood illness (PEDIATRICS,

43:879, 1969) . We operate a similar

in-termediate-care children’s hospital facility at

Stanford, having a parallel historical origin

which has now evolved into a comprehensive

program providing inpatient and outpatient care, teaching and training, and research in the chronic diseases of childhood and youth.

It is a fact, as Dr. Burke points out, that

short-term hospitals have experienced a steady

decrease in the average length of stay to a cur-rent figure of less than 5 days. Meanwhile, the

patient-care model of a specialized hospital center for children with longer-term handicap, who require a broad range of professional

dis-ciplines and expert support personnel, is

emerging. Such a hospital must operate with a

dynamic program philosophy based on early

identification, comprehensive diagnostic and treatment, and longitudinal follow-up.

I also agree with Dr. Burke’s description of

the important contribution the

intermediate-stay hospital can make to pediatric teaching

and research in terms of the understanding of the “complex and multiple” facets of long-term

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hos-1969;44;614

Pediatrics

William H. Tooley