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Choosing surgical illumination
Choosing Surgical Illumination
William C. Beck, MD, FACS, Sayre, Pennsylvania
Surgical illumination results from a system that includes not only the task (operation) light but also the type and quality of the general room lighting and the reflectances of the surfaces in the suite. The ambient room light and the surgical task light should be planned coordinately so that together they will not only provide maximum vision but also be restful when the surgeon looks away from the wound. In studies conducted in our own suite (involving about 20 surgeons at the Robert Packer Hospital in Sayre, Pennsylvania), we found a wide divergence in the amount of light in the field that satisfied surgeons [I] as well as in the quality of the light [2]. Since a relatively small number of surgical task lights are available in the American market, the choice between them should be based on the preferences of the surgeons who will use them, the types of operations for which they will be used and their relative convenience. Minimum requirements as well as the test methods for these have been described by the Illuminating Engineering Society (I.E.S.) [3]. Manufacturers should be asked to explain any lack of conformity to these standards [4]. This report outlines the attributes that should be considered by surgeons and that might affect his choice. Consensus of Choice Improvement in a facility’s lighting cannot, at present, be accomplished simply by installing a new task light. The ambience must be studied first and the capability of providing adequate general lighting for the room must be available. Furthermore, the lighting must be controllable so that the ratios between the task and the surrounding luminance are flexible and adjustable. Some surgical fields are best viewed in a spotlit situation, whereas comfort during prolonged surgery is best achieved by a low brightness ratio of the surgical field to the surrounding area. From the Guthrie Foundation for Medical Research, Guthrie Square, Sayre. Pennsylvania 18840. Requests for reprints should be addressed to William C. Sack, M). Donald Guthrie Foundation for Medical Research, Sayre, Pennsylvania 18840.
Volume 140, Augusi 1980
This ratio is usually interpreted at 5:3:1, going outward from the central point of the task. In new facilities, the room ambience is usually designed by an architect who should abide by the Illuminating Engineering Society’s advice to provide a capability of 200 footcandles in the room. Then the surgical illuminator can be chosen by the surgeon. A variety of surgical task lights are used in surgical suites today, just as a variety of automobiles are seen in the physician’s parking lot. Each is chosen because of its suitability to the needs of the user. The essential difference is that each automobile is used by one surgeon alone, whereas the light may be used by several surgeons. In many hospitals a variety of surgical specialists perform different procedures in the same operating room, and this should be taken into consideration when choosing the fixture. Most surgical lamps are designed for all surgical procedures rather than for one specialty. There is no specific orthopedic, neurosurgical, otologic or urologic light. Adaptability may be built into a light, or one may seem more suitable than another. Similarly, there are no specific guidelines (except in dentistry [5]) for the lighting of special surgical procedures. These can and should be defined. Until this is done each surgeon should review the specifications of a lighting system to see how it fits his own requirements. In fact, it would be advantageous for the surgeon, recognizing the specifications of a lighting system, to operate under it and thus try it out. He may find that supplemental lighting such as a fiberoptic gooseneck or a headlamp would be valuable. Volume of Light and Pattern The I.E.S. defines the minimum light to be delivered to the surgical field as 2,500 footcandles (27 kilolux) when the illuminated site is 42 inches (107 cm) from the lamp cover glass to the surgical field, and the pattern covers 78 square inches or larger (which may be a circular pattern of 10 inch diameter). If the maximum pattern is smaller than 78 square
327
inches, conversion to the 10 inch diameter be made by the following formula:
size can
(Given pattern diameter)2/10 inches or 24 cm2 = Unknown intensity (footcandles)/ Given intensity (footcandles). This pattern size is usually best when it corresponds to the size as well as the shape of the surgical field (round or oval). Most manufacturers provide a means for enlarging or reducing the pattern. The shape can be varied by changing the direction; for example, an oblique light will provide an oval pattern. Adaptation of the light pattern to the size and shape of a wound is not universally used by surgeons. Many surgeons choose the light’s largest field and leave it there even when they are operating through a very small incision. One should also observe changes in intensity when changing field size. The measurement of light intensity of all lights is done at 42 inches for comparison. For some lights, however, this may not be the focal point, and during use the light may be placed at a different level for greatest convenience. Therefore, the surgeon should study the level at which he finds the greatest comfort with the light and then again measure the intensity. For some lights, this will put the beam out of focus,
Figure 1. When a surgical task lamp is placed at a normal distance from the surgical wound, the cavity shouhl be flooded with l&f& In this Instance (as In most), tfta dkstance is 42 inches. tf the distance is signif~antly reduced (in this exampte to 35 inches), the center of tfh9surgicai fiekt may be dark.
328
and the center of the light pattern will no longer be the point of maximum intensity (Figure 1). In fact, there may be a dark spot at the beam’s center. This means some compromise will be necessary. Either the light manuevered to its best pattern or the surgeon’s reach must be altered (for example, by standing on a platform if he wants to manipulate it himself). While the central beam should produce at least 2,500 footcandles, the I.E.S. further prescribes 500 footcandles at the periphery of the 10 inch circle. While this 5:l ratio appears to exceed the 3:l or less ratio considered ideal, the reflectance of a surgical wound is usually 8 percent, while the reflectance of the surrounding drape is usually 35 percent. Thus the eye is still protected from the glare (Figure 2). A white surgical sponge, on the other hand, can cause a glare problem [6,7]. Heat in the Beam Light produces heat in two ways: by the production of invisible infrared rays or by energy transformation of the illuminated object. The former may be removed by means of heat-absorbing filters or heatrejecting reflectors, so that most of the infrared is removed from the beam and discharged through the back of the unit. The I.E.S. defines the maximum amount of energy recommended at the wound level as 25,000 pW/cm2. The manufacturer should be able to assure the buyer that this amount is not unknowingly exceeded. Such an amount is not uncomfortable for the worker and is safe for the patient. Amounts greater than this could be a problem, for example if a distended, thin intestine with a reduced blood supply is exposed to too much heat. Furthermore, the infrared part of the spectrum (800 to 100 nm) should be at an absolute minimum. Surgeons and operating room nurses should be cautioned about what circumstances might cause this level to be exceeded by the system, such as by directing dual site units into the primary field. For large surgical lamps these maximum heat figures require special thermocouples for measurement. For small light sources, however, Brubaker has suggested a simple test which can be aptly applied to fiberoptic illuminators [8,9]. It is carried out using a felt-tipped marker on the flexor side of the wrist, blackening a 1 cm circle. The fiberoptic can be held against this blackened mark and, if no distress or pain is observed in 60 seconds, the light energy is presumably less than 25,000 PW. When buying a fiberoptic lamp, this test should be used even if the exit point of the unit is cool to momentary touch. The statement that the fiberoptic is a “cold light” is meaningless. Light energy can be
The American Journal 01 Surgery
Choosing Surgical Illumination
LA!?GE,MUUIPLE-k-0IhT REFLECTING
LIGKT
’
I
I
L
Face
of
luminarre
I I black !~disc250mmdia
1
I
t
I
60cm.
107 cm.
I
I THEORETICAL FOCAL POINT
I
I
1 I
Removable matte black screening tube 60 mm high x 50 mm dia.
TARGET
Figure 2. Shadow reduction around the head and hands of the surgeon is achieved by bringing the light flux around the obstacle. Ooeratino table /
transformed into heat by a light-absorbing surface such as a black or nonreflecting surface, of which black India ink is a perfect example. Shadow Reduction Most surgical lights are designed to produce beams from a variety of angles so that the interposition of a surgeon’s head or hands will not place the task in darkness (Figure 2). To examine this quality, a prospective buyer should test the light by placing a white sheet of paper on a table and interposing his head and hands as he would in an operating room. He should also interpose other obstructions to represent his assistants. He should put a light meter at the site of the operation and observe the reduction in the light. The I.E.S. has created a simple in vitro test to demonstrate the shadow reduction of an illumination source. The vendor can be called on to demonstrate this test, which is very simple to carry out.* The test, however, takes into consideration only the surgeon’s head as the obstruction, so that the purchaser should also set up a configuration resembling his own surgical team and employing a cavity or surgical field approximately simulating the challenge of his specialty. A model of a surgical exposure, which may be available for demonstration from the salespersons, may be helpful. * In this test 10 percent of the light should reach the bottom of a black tube 2 inches in diameter and 3 inches long at a distance of 42 inches from the light when the beam is obstructed by a disc 10 inches In diameter (representing the surgeon’s head) 23 inches above the table (Figure 3).
Volume 140, August 1980
Figure 3. The I.E.S. Test for shadow reduction. Ten percent of the source llluminatlon should still fall onto the surgical field.
Directionality and Depth of Focus The direction of the light beam must not only dodge the surgeon’s head and hands, but also give adequate illumination to work sites that are not horizontal. I believe that the centerline of the light beam should be from the surgeon’s right ear to his right index finger for right-handed surgeons. This is the ideal in many delicate manual tasks. However, some believe that a better directionality can be achieved by beams from two directions, from the right and left of the surgeon [IO]. The purchaser should, in my opinion, try both. In-ceiling and in-wall sources were first used in Europe (where some are still in use) and in the Orient. They may be directed by motor-driven gimbal arrangements. In the United States fixed ceiling sources are only used in neurosurgical theaters [ 1 I]. I think they may become more popular when rapidly igniting high intensity discharge lights of good color-rendering quality become available. Although the depth of focus is usually adequate, the prospective buyer should be certain that the light purchased will be in focus for the entire depth of his deepest incision. Some lights need to be repositioned as the working site changes. The surgeon should measure the depth from the skin surface of his deepest operation to its bottom, for example, from the skin to the depth of the pouch of Douglas in an
329
Beck
perception of color is a mental phenomenon. The perceived color of a surgical field may not vary greatly at the high luminances of surgical illumination, even with different power distributions of a variety of light sources. Yet it is possible to discern differences in tissue color under different lights.
ll11.
lo9NUMRER OF SURGEONS
R, 6 -
S-
Mobility, Stability and Memory
43ll-
I
COLOR
TEMPERATURE
Figure 4. In our tests we found that surgeons liked to see tissues at about 5,000” K. This graph shows the preferences of a group of surgeons to three light qualities kept at the same intensely.A rating of 8 means “like n very much, ” and a rating of 1 Indicates dislike.
obese patient undergoing choledochostomy, or from the skin to the posterior chest wall during pneumonectomy. When there is nothing on the operating table except a white sheet, move a light back and forth for a similar distance and see that the edge of the light pattern remains sharp and that the center does not darken. A light meter in the field will quantitate the judgment. The depth of focus is important if the surgeon does not want to adjust the lamp as the operation progresses.
Color of the Light White light is a combination of colors and actually may contain a variety of source color. If one heats a poker to incandescence it will emit light, just as a light bulb does. As the temperature rises, the color will change from red to yellow, then to white or even bluish-white heat. The color of a full radiator (black body) being heated can be related to its absolute temperature in degrees Kelvin for reference purposes. We know of no test that reveals which color of light is the best for the performance of surgical operations, but most of the surgeons we tested prefer light at about 5,OOO”K (Figure 4). This is approximately the color of noon sunlight. It is also the color accepted by the Graphic Arts Industry as a standard (ANSI PH2.32/172). There are also some surgeons who prefer light at 3,500 and 6,500°K. If possible, buyers should determine their own preference but should realize that there are also other preferences. The vendor will be able to describe the color characteristics of his light, and the surgeon should observe tissues under different lights. The
330
The light in its gimballed mounting should respond easily to positioning by the surgeon or by the nonsterile circulating nurse. It should remain in position without drift. If a sterile handle is used, the surgeon should test the ease with which the light is manipulated and the full range of such manipulation. If the drift protection is adjustable, then that should be explained by the salesman. The flexibility of the mounting and positioning should be tested. The security of the handle should also be ascertained so that it cannot drop off spontaneously. If flammable anesthetics are permitted in that operating room, no electrical part of the lamp may be lowered below 5 feet from the floor. However, if the room is designated off-limits for flammable anesthetics, the lamp may be lowered below 5 feet, thus permitting better viewing for vaginal surgery, for example.
Safety Features All lamps essential to surgical viewing in the operating room should be connected with an emergency secondary power system capable of automatic initiation within 10 seconds. This, of course, is an attribute of the hospital system, not the light. Also, all lighting systems should be prepared for lamp burnout with a second filament or the ability to provide about the same light with a replacement lamp within 10 seconds. The protection against burnout is important, and one should remember that the burned out lamp may be very hot.
Secondary Field Exposures In many operations performed today, it is necessary to provide full surgical illumination over a second or third field. For this purpose most surgical units can be purchased with satellite units. If used, these units should not be a part of the normal primary field illumination. Units requiring more than one lamphead to illuminate the primary site must, therefore, have a third for dual exposure.
Summary (1). Lighting systems for the surgical task are combinations of ambient room lighting to comple-
The American Journal of Surgery
Choosing Surgical Illumination
ment the operating task light. The two must match to produce a good effect. (2) Only a few surgical task lights are available, and their characteristics and relative merits should be studied. (3) Ideally the surgeon should test the task light to judge its suitability for his taste. References 1. Beck WC. How much light does the surgeon want? JIES 1974; 3:346. 2. Beck WC, Schreckendgust J, Geffert J. The color of the surgeon’s light. Light Design Appl 1979; 955. 3. Beck WC. Committee on health care facilities: Lighting for health care facilities, CP-29. New York: Illuminating Engi-
Volume 140, August lgS0
neering Society, 1976;17-24. 4. Beck WC. The physician’s role in quality control of medical devices. JAMA 1979;241:56. 5. Preston JD, Ward LC, Bobrick M. Light and lighting in the dental office. Dent Clin North Am 1978;22:431-51. 6. Beck WC, Goldhamer RD. Discomfort, glare and the surgical sponge. Guthrie Bull 1971;40:57. 7. Ringrose NH. White sponges and surgical wound illumination. Med J Aust 1976;2:893. 8. Brubaker JD. Illumination hazards and safety standards in medicine and surgery. Private distribution, 1977. J. D. Brubaker, 949 Sherman Ave., Evanston, IL 60202. 9. Hardy JD, Jacobs I, Mugatroyd D. Spectral transmittance of human skin. J Appl Physiol 1962;17:693. 10. Fisher KJ. Single-source surgical luminaire employs folded optical concept. LDA 1978;8:38. 11. Fudes J. Operating room lighting provides pinpoint control. Electrical Construction and Maintenance, 1972; 58.
331
William C. Beck, MD, FACS, Sayre, Pennsylvania
Surgical illumination results from a system that includes not only the task (operation) light but also the type and quality of the general room lighting and the reflectances of the surfaces in the suite. The ambient room light and the surgical task light should be planned coordinately so that together they will not only provide maximum vision but also be restful when the surgeon looks away from the wound. In studies conducted in our own suite (involving about 20 surgeons at the Robert Packer Hospital in Sayre, Pennsylvania), we found a wide divergence in the amount of light in the field that satisfied surgeons [I] as well as in the quality of the light [2]. Since a relatively small number of surgical task lights are available in the American market, the choice between them should be based on the preferences of the surgeons who will use them, the types of operations for which they will be used and their relative convenience. Minimum requirements as well as the test methods for these have been described by the Illuminating Engineering Society (I.E.S.) [3]. Manufacturers should be asked to explain any lack of conformity to these standards [4]. This report outlines the attributes that should be considered by surgeons and that might affect his choice. Consensus of Choice Improvement in a facility’s lighting cannot, at present, be accomplished simply by installing a new task light. The ambience must be studied first and the capability of providing adequate general lighting for the room must be available. Furthermore, the lighting must be controllable so that the ratios between the task and the surrounding luminance are flexible and adjustable. Some surgical fields are best viewed in a spotlit situation, whereas comfort during prolonged surgery is best achieved by a low brightness ratio of the surgical field to the surrounding area. From the Guthrie Foundation for Medical Research, Guthrie Square, Sayre. Pennsylvania 18840. Requests for reprints should be addressed to William C. Sack, M). Donald Guthrie Foundation for Medical Research, Sayre, Pennsylvania 18840.
Volume 140, Augusi 1980
This ratio is usually interpreted at 5:3:1, going outward from the central point of the task. In new facilities, the room ambience is usually designed by an architect who should abide by the Illuminating Engineering Society’s advice to provide a capability of 200 footcandles in the room. Then the surgical illuminator can be chosen by the surgeon. A variety of surgical task lights are used in surgical suites today, just as a variety of automobiles are seen in the physician’s parking lot. Each is chosen because of its suitability to the needs of the user. The essential difference is that each automobile is used by one surgeon alone, whereas the light may be used by several surgeons. In many hospitals a variety of surgical specialists perform different procedures in the same operating room, and this should be taken into consideration when choosing the fixture. Most surgical lamps are designed for all surgical procedures rather than for one specialty. There is no specific orthopedic, neurosurgical, otologic or urologic light. Adaptability may be built into a light, or one may seem more suitable than another. Similarly, there are no specific guidelines (except in dentistry [5]) for the lighting of special surgical procedures. These can and should be defined. Until this is done each surgeon should review the specifications of a lighting system to see how it fits his own requirements. In fact, it would be advantageous for the surgeon, recognizing the specifications of a lighting system, to operate under it and thus try it out. He may find that supplemental lighting such as a fiberoptic gooseneck or a headlamp would be valuable. Volume of Light and Pattern The I.E.S. defines the minimum light to be delivered to the surgical field as 2,500 footcandles (27 kilolux) when the illuminated site is 42 inches (107 cm) from the lamp cover glass to the surgical field, and the pattern covers 78 square inches or larger (which may be a circular pattern of 10 inch diameter). If the maximum pattern is smaller than 78 square
327
inches, conversion to the 10 inch diameter be made by the following formula:
size can
(Given pattern diameter)2/10 inches or 24 cm2 = Unknown intensity (footcandles)/ Given intensity (footcandles). This pattern size is usually best when it corresponds to the size as well as the shape of the surgical field (round or oval). Most manufacturers provide a means for enlarging or reducing the pattern. The shape can be varied by changing the direction; for example, an oblique light will provide an oval pattern. Adaptation of the light pattern to the size and shape of a wound is not universally used by surgeons. Many surgeons choose the light’s largest field and leave it there even when they are operating through a very small incision. One should also observe changes in intensity when changing field size. The measurement of light intensity of all lights is done at 42 inches for comparison. For some lights, however, this may not be the focal point, and during use the light may be placed at a different level for greatest convenience. Therefore, the surgeon should study the level at which he finds the greatest comfort with the light and then again measure the intensity. For some lights, this will put the beam out of focus,
Figure 1. When a surgical task lamp is placed at a normal distance from the surgical wound, the cavity shouhl be flooded with l&f& In this Instance (as In most), tfta dkstance is 42 inches. tf the distance is signif~antly reduced (in this exampte to 35 inches), the center of tfh9surgicai fiekt may be dark.
328
and the center of the light pattern will no longer be the point of maximum intensity (Figure 1). In fact, there may be a dark spot at the beam’s center. This means some compromise will be necessary. Either the light manuevered to its best pattern or the surgeon’s reach must be altered (for example, by standing on a platform if he wants to manipulate it himself). While the central beam should produce at least 2,500 footcandles, the I.E.S. further prescribes 500 footcandles at the periphery of the 10 inch circle. While this 5:l ratio appears to exceed the 3:l or less ratio considered ideal, the reflectance of a surgical wound is usually 8 percent, while the reflectance of the surrounding drape is usually 35 percent. Thus the eye is still protected from the glare (Figure 2). A white surgical sponge, on the other hand, can cause a glare problem [6,7]. Heat in the Beam Light produces heat in two ways: by the production of invisible infrared rays or by energy transformation of the illuminated object. The former may be removed by means of heat-absorbing filters or heatrejecting reflectors, so that most of the infrared is removed from the beam and discharged through the back of the unit. The I.E.S. defines the maximum amount of energy recommended at the wound level as 25,000 pW/cm2. The manufacturer should be able to assure the buyer that this amount is not unknowingly exceeded. Such an amount is not uncomfortable for the worker and is safe for the patient. Amounts greater than this could be a problem, for example if a distended, thin intestine with a reduced blood supply is exposed to too much heat. Furthermore, the infrared part of the spectrum (800 to 100 nm) should be at an absolute minimum. Surgeons and operating room nurses should be cautioned about what circumstances might cause this level to be exceeded by the system, such as by directing dual site units into the primary field. For large surgical lamps these maximum heat figures require special thermocouples for measurement. For small light sources, however, Brubaker has suggested a simple test which can be aptly applied to fiberoptic illuminators [8,9]. It is carried out using a felt-tipped marker on the flexor side of the wrist, blackening a 1 cm circle. The fiberoptic can be held against this blackened mark and, if no distress or pain is observed in 60 seconds, the light energy is presumably less than 25,000 PW. When buying a fiberoptic lamp, this test should be used even if the exit point of the unit is cool to momentary touch. The statement that the fiberoptic is a “cold light” is meaningless. Light energy can be
The American Journal 01 Surgery
Choosing Surgical Illumination
LA!?GE,MUUIPLE-k-0IhT REFLECTING
LIGKT
’
I
I
L
Face
of
luminarre
I I black !~disc250mmdia
1
I
t
I
60cm.
107 cm.
I
I THEORETICAL FOCAL POINT
I
I
1 I
Removable matte black screening tube 60 mm high x 50 mm dia.
TARGET
Figure 2. Shadow reduction around the head and hands of the surgeon is achieved by bringing the light flux around the obstacle. Ooeratino table /
transformed into heat by a light-absorbing surface such as a black or nonreflecting surface, of which black India ink is a perfect example. Shadow Reduction Most surgical lights are designed to produce beams from a variety of angles so that the interposition of a surgeon’s head or hands will not place the task in darkness (Figure 2). To examine this quality, a prospective buyer should test the light by placing a white sheet of paper on a table and interposing his head and hands as he would in an operating room. He should also interpose other obstructions to represent his assistants. He should put a light meter at the site of the operation and observe the reduction in the light. The I.E.S. has created a simple in vitro test to demonstrate the shadow reduction of an illumination source. The vendor can be called on to demonstrate this test, which is very simple to carry out.* The test, however, takes into consideration only the surgeon’s head as the obstruction, so that the purchaser should also set up a configuration resembling his own surgical team and employing a cavity or surgical field approximately simulating the challenge of his specialty. A model of a surgical exposure, which may be available for demonstration from the salespersons, may be helpful. * In this test 10 percent of the light should reach the bottom of a black tube 2 inches in diameter and 3 inches long at a distance of 42 inches from the light when the beam is obstructed by a disc 10 inches In diameter (representing the surgeon’s head) 23 inches above the table (Figure 3).
Volume 140, August 1980
Figure 3. The I.E.S. Test for shadow reduction. Ten percent of the source llluminatlon should still fall onto the surgical field.
Directionality and Depth of Focus The direction of the light beam must not only dodge the surgeon’s head and hands, but also give adequate illumination to work sites that are not horizontal. I believe that the centerline of the light beam should be from the surgeon’s right ear to his right index finger for right-handed surgeons. This is the ideal in many delicate manual tasks. However, some believe that a better directionality can be achieved by beams from two directions, from the right and left of the surgeon [IO]. The purchaser should, in my opinion, try both. In-ceiling and in-wall sources were first used in Europe (where some are still in use) and in the Orient. They may be directed by motor-driven gimbal arrangements. In the United States fixed ceiling sources are only used in neurosurgical theaters [ 1 I]. I think they may become more popular when rapidly igniting high intensity discharge lights of good color-rendering quality become available. Although the depth of focus is usually adequate, the prospective buyer should be certain that the light purchased will be in focus for the entire depth of his deepest incision. Some lights need to be repositioned as the working site changes. The surgeon should measure the depth from the skin surface of his deepest operation to its bottom, for example, from the skin to the depth of the pouch of Douglas in an
329
Beck
perception of color is a mental phenomenon. The perceived color of a surgical field may not vary greatly at the high luminances of surgical illumination, even with different power distributions of a variety of light sources. Yet it is possible to discern differences in tissue color under different lights.
ll11.
lo9NUMRER OF SURGEONS
R, 6 -
S-
Mobility, Stability and Memory
43ll-
I
COLOR
TEMPERATURE
Figure 4. In our tests we found that surgeons liked to see tissues at about 5,000” K. This graph shows the preferences of a group of surgeons to three light qualities kept at the same intensely.A rating of 8 means “like n very much, ” and a rating of 1 Indicates dislike.
obese patient undergoing choledochostomy, or from the skin to the posterior chest wall during pneumonectomy. When there is nothing on the operating table except a white sheet, move a light back and forth for a similar distance and see that the edge of the light pattern remains sharp and that the center does not darken. A light meter in the field will quantitate the judgment. The depth of focus is important if the surgeon does not want to adjust the lamp as the operation progresses.
Color of the Light White light is a combination of colors and actually may contain a variety of source color. If one heats a poker to incandescence it will emit light, just as a light bulb does. As the temperature rises, the color will change from red to yellow, then to white or even bluish-white heat. The color of a full radiator (black body) being heated can be related to its absolute temperature in degrees Kelvin for reference purposes. We know of no test that reveals which color of light is the best for the performance of surgical operations, but most of the surgeons we tested prefer light at about 5,OOO”K (Figure 4). This is approximately the color of noon sunlight. It is also the color accepted by the Graphic Arts Industry as a standard (ANSI PH2.32/172). There are also some surgeons who prefer light at 3,500 and 6,500°K. If possible, buyers should determine their own preference but should realize that there are also other preferences. The vendor will be able to describe the color characteristics of his light, and the surgeon should observe tissues under different lights. The
330
The light in its gimballed mounting should respond easily to positioning by the surgeon or by the nonsterile circulating nurse. It should remain in position without drift. If a sterile handle is used, the surgeon should test the ease with which the light is manipulated and the full range of such manipulation. If the drift protection is adjustable, then that should be explained by the salesman. The flexibility of the mounting and positioning should be tested. The security of the handle should also be ascertained so that it cannot drop off spontaneously. If flammable anesthetics are permitted in that operating room, no electrical part of the lamp may be lowered below 5 feet from the floor. However, if the room is designated off-limits for flammable anesthetics, the lamp may be lowered below 5 feet, thus permitting better viewing for vaginal surgery, for example.
Safety Features All lamps essential to surgical viewing in the operating room should be connected with an emergency secondary power system capable of automatic initiation within 10 seconds. This, of course, is an attribute of the hospital system, not the light. Also, all lighting systems should be prepared for lamp burnout with a second filament or the ability to provide about the same light with a replacement lamp within 10 seconds. The protection against burnout is important, and one should remember that the burned out lamp may be very hot.
Secondary Field Exposures In many operations performed today, it is necessary to provide full surgical illumination over a second or third field. For this purpose most surgical units can be purchased with satellite units. If used, these units should not be a part of the normal primary field illumination. Units requiring more than one lamphead to illuminate the primary site must, therefore, have a third for dual exposure.
Summary (1). Lighting systems for the surgical task are combinations of ambient room lighting to comple-
The American Journal of Surgery
Choosing Surgical Illumination
ment the operating task light. The two must match to produce a good effect. (2) Only a few surgical task lights are available, and their characteristics and relative merits should be studied. (3) Ideally the surgeon should test the task light to judge its suitability for his taste. References 1. Beck WC. How much light does the surgeon want? JIES 1974; 3:346. 2. Beck WC, Schreckendgust J, Geffert J. The color of the surgeon’s light. Light Design Appl 1979; 955. 3. Beck WC. Committee on health care facilities: Lighting for health care facilities, CP-29. New York: Illuminating Engi-
Volume 140, August lgS0
neering Society, 1976;17-24. 4. Beck WC. The physician’s role in quality control of medical devices. JAMA 1979;241:56. 5. Preston JD, Ward LC, Bobrick M. Light and lighting in the dental office. Dent Clin North Am 1978;22:431-51. 6. Beck WC, Goldhamer RD. Discomfort, glare and the surgical sponge. Guthrie Bull 1971;40:57. 7. Ringrose NH. White sponges and surgical wound illumination. Med J Aust 1976;2:893. 8. Brubaker JD. Illumination hazards and safety standards in medicine and surgery. Private distribution, 1977. J. D. Brubaker, 949 Sherman Ave., Evanston, IL 60202. 9. Hardy JD, Jacobs I, Mugatroyd D. Spectral transmittance of human skin. J Appl Physiol 1962;17:693. 10. Fisher KJ. Single-source surgical luminaire employs folded optical concept. LDA 1978;8:38. 11. Fudes J. Operating room lighting provides pinpoint control. Electrical Construction and Maintenance, 1972; 58.
331