In a fiber-optic green-system laryngoscope, the light source sits in the handle head and shines into the blade’s light guide when the blade clicks into the working position. Two kinds of light source are in use, xenon lamps and LEDs. Both work with green-system blades, but they behave differently day to day.
How each works
A xenon lamp in a laryngoscope handle is a small filament lamp filled with xenon gas, often with halogen. The gas lets the tungsten filament run hotter and brighter than in an ordinary vacuum bulb. It is not the xenon arc lamp used in some endoscopy light sources.
An LED, or light-emitting diode, is a semiconductor that gives off light when current flows through it; most white LEDs use a blue LED with a phosphor coating. Many LED handles also contain a small driver circuit that controls the current.
When ISO 7376 was revised in 2020, its requirements for filament lamps were removed, as LEDs had almost entirely replaced them. Xenon handles are still in service and still sold, though, so the comparison still matters.
Light colour
Filament lamps give a warm white light, typically around 3,000 K, with a colour rendering index close to 100, so colours look natural. LED light depends on the LED chosen: many are cooler and whiter, and colour rendering ranges from moderate to very good. Light colour affects how tissue looks, so ask for both figures and let clinicians compare samples.
Consistency
As batteries run down, a filament lamp gradually dims and turns yellower. An LED with a regulated driver tends to hold its brightness until the battery is nearly flat, then fades or stops more quickly; without regulation, it also dims as the voltage falls. With either type, weak batteries are a common cause of poor light, so a light check belongs in the routine trolley check.
Heat
A filament lamp turns most of its power into heat. An LED turns a larger share into light, so for the same brightness it runs cooler and draws less current. In the green system, with either type, the lamp stays in the handle and never enters the patient’s mouth.
Battery life
Because LEDs draw less current for the same light, batteries usually last considerably longer in an LED handle, though run time depends on the light source, the driver, the batteries and how the handle is used.
Check the voltage too. 2.5 V handles usually run on standard dry cells, while 3.5 V handles usually take a rechargeable battery and a charger. A lamp or LED head made for one voltage should not be used at the other unless its maker says so.
Lamp replacement
Filament lamps wear out, so departments with xenon handles keep spare lamps of the correct type and voltage. LEDs last far longer and rarely need replacing; when one fails, the whole LED head is usually changed. Some makers offer LED heads that replace the xenon lamp in existing handles. Use only versions the handle maker approves, or that the supplier confirms are compatible with your handle model.
What to ask a supplier
- How was light output measured: in lumens from the handle or in lux at the blade tip, with which blade, at what distance, with new or fully charged batteries, and after how long switched on? Was the ISO 7376 test method used?
- What are the colour temperature and the colour rendering index?
- Is the light regulated, and how does it behave as the batteries run down?
- Which battery type, size and voltage does the handle use? Is there a rechargeable option, and what charger does it need?
- What is the expected lamp life, and what are the part numbers for spare lamps or LED heads?
- How are the handle and its light source reprocessed, according to the IFU?
To compare handles with those you already use, send our export team the makes and models in service.