Surgical lighting in operation theatre

SURGICAL LIGHTING IN OPERATION THEATRE
OT LIGHTS
SELECTION OF SURGICAL LIGHTING

1. SURGICAL LIGHTING IN OPERATION THEATRE DR. AMOL GAIKWAD MBBS MS(ORTHOPAEDICS) CONSULTANT ORTHOPAEDIC SURGEON

2. The human eye is best adapted for vision in natural light.  Intense efforts have been taken to generate lighting systems which can emulate natural lighting. The human eye works primarily in contrast to identify objects and to give them context. When contrast is lost, visual performance and hence human performance begins to fail. Effective and successful performance within the operating theatre is enhanced by having lighting which does not cause visual, operational and environmental difficulties such as glare, shadowing or visual stress

3. The ability to adjust these lighting levels and change their characteristics will enable theatre staff to be more effective . Incorrect or poor lighting can impact on the patient, through poor performance and impaired effectiveness which may cause lengthened procedures through uncertainty or even errors. Surgical lighting is vitally important within the operating theatre to allow those working to have a clear vision of the surgical site and working area, and able to rely on the performance of the lighting equipment.

4. Lighting Selection An important decision to be made when investing in theatre lights is whether each operating theatre will need identical lighting equipment or whether the lighting will need to be specific to surgical disciplines . Selection Team Healthcare professionals involved in the decision making include: Surgeons : Those from different specialties will have different illumination needs. Nurses and OT Assistants : They are more concerned about the maneuverability, adjustment ease and simplicity of changing light handles. Biomedical Engineers : They will look into the technical specifications, quality of the product, the electrical supply, mounting and suspension of lights. Architects & Engineers : They will look into aesthetics and structural aspects of the installation. Purchase & Finance : They will negotiate and look into taxes and payments.

5. Basic Objectives There are three key areas under which decisions and priorities should be made when determining a suitable operating theatre light. These are: Adjustability : The design of the lighting unit and how it can adapt to meet individual requirements. Brightness : The amount of light delivered by a source in order to illuminate a specific surgical area. Control : Selection of a good design and an appropriate light source will help the system integrate into the operating theatre environment. However, flexibility and adjustability in the lighting system (amount of light and spread of light)will accommodate a wider range of tasks and activities. Each of these elements will have an influence on the purchasing decisions for operating theatre lighting.

6. Technical Considerations Lux (lx): The unit of measurement for the amount of light at a given point and is measured using a lux meter at that point. One lux is equal to one lumen per square meter. Colour Rendition Index (Ra & R9): The effect the light source has on the appearance of coloured objects (tissue for example). This is a measure of the quality of light; natural daylight has a CRI value of 100. The closer an operating theatre light CRI value is to 100, the better its ability to render true colours to the human eye. It is important to appreciate how well the light renders a saturated deep red colour (R9) which will allow the surgeon to recognize details better in the area of the wound and to distinguish between tissue colours and arterial or venous blood.

7. Colour Temperature (K): The perceived coolness or warmth of light measured in Kelvin. Some LEDs permit the ability to adjust colour temperature, which allows a surgical team to manipulate the light characteristics and hence facilitate tissue differentiation. Central Illuminance ( Ec ): The Illuminance (lx) at 1m distance from the light emitting surface in the light-field center and is measured in lumens per square meter. For good performance, it is important that the light is capable of achieving both a high illuminance and good colour rendition simultaneously. Light Field Centre : The point in the light field (lighted area) where illuminance reaches maximum lux. It is the reference point for most measurements. Depth of Illumination : The distance under the light emitting area where the illumination reaches20% of the central illuminance .

8. Shadow Dilution : Refers to the light’s ability to minimize the effect of obstructions. An absence of cast shadow or coloured shadow is described as perfect shadow dilution. Light Field Diameter : Diameter of the light field around light field center, ending where the illuminance reaches 10% of central illuminance . Fail Safe : The backup possibility in case of interruption of the main power supply.

9. LUX Unit for the amount of visible light measured by a luxmeter at a certain point. Central illuminance ( Ec ) Illuminance (measured in lux) at 1m distance from the light emitting surface in the light field centre . Light field centre Point in the light field (lighted area) where illuminance reaches maximum lux intensity. It is the reference point for most measurements. Depth of illumination The distance between the points of 20% illumination intensity above and below the center point. From the point of maximum illumination, which is the center of the light field 1 meter from the light-emitting surface, the photometer is moved toward the light until the light intensity measured falls to 20% of the maximum value. The distance between the center and this point is defined as L1. The similarly measured distance in the direction away from the light is L2. The depth of illumination without needing to refocus is the sum of the two distances L1 and L2. In the second edition of the IEC standard, published in 2009, the threshold value was revised from 20% to 60 %.

10. Norms and requirements for surgical light The International Electrotechnical Commission (IEC) created the document IEC 60601-2-41 – Particular requirements for the basic safety and essential performance of surgical luminaires and luminaires for diagnosis, 2009 to establish norms and guidelines for the characteristics of a surgical and examination light to secure safety for the patient as well as lower the risk to a reasonable level when the light is used according to the user manual. Some of the standards for surgical lightheads are the following: Homogenous light : The light should offer good illumination on a flat, narrow or deep surface in a cavity, despite obstacles such as surgeons' heads or hands. Lux : The central illuminance should be between 160,000 and 40,000 lux. Light field diameter : The D50 diameter should be at least 50% of D10. Colour rendition : For the purpose of distinguishing true tissue colour in a cavity, the colour rendering index (Ra) should be between 85 and 100. Backup possibility : In case of interruption of the power supply, the light should be restored within 5 seconds with at least 50% of the previous lux intensity, but not less than 40,000 lux. Within 40 seconds the light should be completely restored to the original brightness.

11. Surgical lighting configurations may include ceiling-mounted, wall-mounted, or on floor stand. Depending on the model, a surgical light may also be used in all three configurations. A ceiling-mounted light can be mounted on a fixed point on the ceiling of a procedure room . Similarly, wall-mounted lights are mounted on a wall of the OR. The wall-mounted configuration is more often used with examination lights versus surgical lights. For greater mobility, floor standing surgical lights are standalone and typically on wheels enabling them to move room to room.

12. Lighting Specifications There is a range of technical specifications which are important to be aware of when making purchasing decisions. Lamp Technology There are typically three basic types of lamps used in an operating theatre environment – Incandescent, Gas Discharge and Light Emitting Diodes (LED). Incandescent and gas discharge lamps have traditionally been the main lamp types, utilizing halogen, tungsten, xenon, and quartz. However, other types of lighting now emerging onto the market in several forms, particularly LEDs. LEDs are small semiconductors which emit light when an electrical current is passed through them. An LED unit contains multiple lamps, which can either be all white, or a combination of white and multi-colored lamps. Using a combination of colours allows the surgeon to adjust the lamps to produce the desired colour output

13. Incandescent Lighting Halogen bulbs were historically considered conventional surgical lights and utilize a type of incandescent bulb filled with halogen gas to produce light inside of the lamp. Halogen enables the filament to run at a higher temperature because, although the tungsten is evaporated off the filament faster at the higher temperature, the halogen chemically reacts with the evaporated tungsten to form a tungsten halogen compound which diffuses back to the filament where the higher temperature causes it to separate into tungsten and halogen, depositing the tungsten back on the filament. lower filament correlated color temperature at 3,000K gives them their typical orange-yellow, warm appearing cast rather than white. Standard halogen lights have a short life span which averages approximately 1,000 to 3,000 hours and often dies abruptly. When lit 24 hours a day, seven days a week, this translates into about 6 months of life. Changing bulbs every six months can become costly to an organization over time. If halogen lamps are touched with bare hands, even when cool, the oil from the person’s fingers can heat thereby shortening the life of the bulb.

14. The glare from halogen lights became a risk as it caused fatigue and eye strain when surgeons looked away from the surgical site into glaring lights and needed time for their eyes to adjust when refocusing their attention on the surgical cavity. LED Lighting In the early 2000s, LED became a standard offering in many industries, including ORs and other procedural areas, and surpassed conventional halogen light sources as the preferred light source used during surgical procedures. They are solid-state semiconductor devices that emit light as currents flow through it. LEDs can be extremely small, durable, reliable and have a much higher bulb-life rate than conventional lighting . The light output of LEDs is determined by the current through the semiconductor and its temperature and when using the maximum current recommended by the manufacturer, LEDs can have a long life of up to 60,000 hours.

15. High-Intensity Discharge (HID) Lighting Gas-discharge lamps generate light by sending an electrical discharge through ionized gas. High-Intensity discharge (HID) lights are a type of electrical gas-discharge that use an electric arc to produce intense light. REQUIREMENTS FOR SURGICAL LIGHTS Surgical light requirements vary depending on the type, brand, and model of the lighting system. The brightness of a surgical light head is measured in Lux and typically does not exceed 160,000 Lux. The approximate dimensions are 400-700mm for a light head diameter and the approximate weight is 45kg. The weight can vary depending on the number of light heads attached to the system . The lifespan of a surgical light is measured in its L70 value, which is how long the light will last until its brightness is 70% of its original value . Today's surgical lights typically last between 40,000 to 60,000 hours of use.

16. Lighting Design Operating theatre lights are designed in single and multiple light heads which can be fixed in different ways within the operating theatre, for instance all, ceiling, track mounted or a floor standing version with a mobile base. Major operating lights should always be supplied as a “main” and “satellite” pair, as their use in combination is the major tool in reducing shadow from the surgical team. Single lamps, used in isolation may not provide the required light output desired for a surgical procedure.

17. Radiant energy defines the radiation being directed to the patient, including the visible light energy which is the largest component. Heat from the light can also affect other equipment including laminar airflow (ultra clean ventilation), and thermal buoyancy. The shape of some lamp heads or systems can affect the laminar airflow when moved. Some light sources, such as halogen lighting, are inefficient because of the amount of energy consumed which leads to heat. LED lights offer significant benefits in this respect since they do not produce heat at the light source. The life of the light source is also important, with LED lamps offering a service life far greater than incandescent light sources. This can impact greatly the cost of the light over its service life. To minimize damaging heat effects, surgical lights are designed to dissipate the heat at the light source away into the operating room. This is performed in a number of ways including the use of filters or lenses that pass visible light but not heat.

18. Light Arms The light arms which hold the light head is a very important factor to be considered before the purchase of operation theatre lights. They should maintain the position of the light head without drifting. They should not be smooth and not entangle. They should be easy to maneuver with one hand of the surgeon or nurse. The arm length should be such that they can reach any part of the body where the surgeon wants to operate. Audio Visual Equipment Many surgical lights are designed to be an integrated component of the whole operating theatre environment. Some manufacturers offer video cameras, monitors and mics mounted directly in the light head or on surrounding equipment.

19. Cabling, Power Source and Fail Safe Trip hazards should be eliminated as far as possible. Cabling of AV accessories such as cameras and monitors should be integrated into the operating theatre light arms and not attached externally where they are an infection control hazard and a trip hazard. There are requirements to ensure that operating lights are ‘ equipotential’ bonded . This ensures that the light is earthed to the same clean earth potential as other equipment in the room. Major operating lights should always be installed with separate and parallel power supply systems to ensure that one lamp lead will continue to function in the event of the failure of any one component.

20. Infection Control It is important that lighting equipment, especially handles can be sterilized. The ease of cleaning the lighting systems should be investigated before purchase. The design of operating theatre lights should minimize cracks, crevices, and visible fixings so as to provide clean, clear easy surfaces for cleaning. Surfaces for the build-up of dust and debris should be minimized . The design should also take into account an easy, effective and safe cleaning regime without the requirement for aggressive chemicals, whilst providing sterile controls for movement and control of the light functions. Warranty and Maintenance It is important that practices and procedures are put in place to ensure safe operating of medical equipment. It is recommended that operating lights have 6 monthly safety inspections on all elements of the device. If the theatre light uses a battery backup system, this must also be checked. A three-hour battery backup is a minimum standard; systems should be checked as part of the service to make sure it is functioning correctly. A full discharge test should be performed to establish that the lights can still operate for at least three hours from a full charge.