Infant Incubators, Warmers, and Bili Lights

 Infant incubator heat blowers, located underneath the mattress, get noisy with age. To keep babies and clinical staff happy, check the blowers during the preventive maintenance cycle and replace them if necessary.

Infant incubators and warmers are two of the oldest medical devices in use. Their basic designs were established in the 1920s and have not changed too much over the years. Additional features have been added, but the basic principles of use are still the same.

After being delivered, infants are exposed to room temperatures that are much lower than those inside the womb. Infants lose body temperature via conduction, which would occur if they were placed on a cooler surface, and convection, which happens as air moves past the body. It often takes neonates a few hours to adequately regulate their body temperature. Prolonged cold stress of a neonate can cause or contribute to oxygen deprivation, hypoglycemia, and metabolic acidosis, to name a few. Keeping a neonate warm is critical, and technology helps, since blankets alone do not perform satisfactorily.

Infant Incubators
Basically, the infant incubator is a plastic box with a front door that allows clinical staff to put the neonate inside and a series of portholes that allow clinical staff to care for the baby. A heater under the unit’s mattress warms the temperature inside the incubator. Most modern units use a blower system to circulate the air. With age, these blower systems—fans or squirrel cages—get noisy and should be replaced. While we are not aware of a requirement limiting the maximum acceptable noise level inside the incubator, we replace the blower system once the sound level reaches 60 decibels (dB). Most blower systems have lubrication-free bearings, so oiling often is not an option to reduce noise.

The heater can be controlled in one of three ways: 1) manually, using a rheostat or selector switch; 2) automatically, via an air-temperature sensor; or 3) automatically, via a sensor placed on the neonate. It is not unusual for all three methods to be used during a patient cycle. For instance, the incubator might be started in the manual mode to warm up to a certain point, then switched to the air mode for a period of time when the neonate is placed inside it, and finally switched to the automatic mode when the sensor is placed on the neonate. The best placement for the temperature sensor is over the liver; since the liver has the largest concentration of blood near the body surface, it most accurately reflects the neonate’s core temperature.

The air inside the incubator is generally humidified and enriched with oxygen. Care must be taken on oxygen levels; a pulse oximeter often is used to monitor the oxygen saturation of the newborn. If an internal humidifier is used, cleaning between patients is critical, since warmth, moisture, and oxygen promote the growth of bacteria.

During the preventive maintenance (PM) process on an incubator, the mechanical latching on the door and portholes should be checked, along with the temperature ranges and alarms. The alarms should be tested in all modes of operation (manual, air, and skin sensor). The chamber and heater areas also should be checked for mercury. The presence of mercury is generally traced to a broken thermometer. Mercury vapors are very dangerous to neonates, and great care must be taken to protect them from these vapors.

Infant Warmers
Different infant warmer designs feature various types of heating elements, including quartz heating rods, heat lamps, radiant panels, and resistance heating rods. Most are controlled by a rheostat or resistor-selection switch, or a surface sensor placed on the infant over the liver. The use of the manual control should be limited to when the surfaces are being warmed or when a procedure is being performed on the neonate. One disadvantage of a warmer compared to an incubator is that the patient on a warmer loses more fluids than one would inside an incubator. Therefore, clinical staff must closely monitor the neonate’s hydration level when it is on a warmer. Also, because of the infrared wavelengths associated with the warmer, the neonate’s eyes must be protected; the waves can damage the retinas.

On most warmers, there is a set distance between the heating element and the surface on which the infant is placed. The heat is focused to that distance, and the heat may vary from the center of the patient surface to the edges; therefore, if the neonate squirms around, it may not receive consistent warming. The side panels and foot panels always must be in the “up” position when the neonate is not being worked on; newborn patients may be small, but they move around and can fall off the warmers.

As with incubators, warmers should be tested in all modes and for all alarm conditions. Both units have a factory-set, upper-limit thermostat that can range between 105°F and 107°F. Be sure to check the manual before testing the unit so that you test to the correct temperature.

Some warmers have what is called a procedure light; this is another heat source, and it should not be used for a long period of time as it can overheat the baby.

Some very old warmers used heat lamps as the heat source. These were difficult to control and have not been produced in many years. Please do not confuse the “heat lamps on a mobile pole” with an infant warmer. They may be in your inventory, but they are not infant warmers. They are warming lamps—best used for warming French fries, not neonates.

Bili Lights
When a neonate’s immature liver has trouble breaking down excess bilirubin in the bloodstream, the baby will develop a yellow/orange tinge on the skin. This condition, called jaundice, also can be caused by problems with the liver’s bile ducts. In the 1940s, it was discovered that exposing jaundiced neonates to light in the 424–475 nanometer (nM) range reduced the inflated bilirubin levels in the bloodstream. It also was reported that by placing neonates on a windowsill to receive direct sunlight, bilirubin levels could also be reduced.

In testing bili lights, or bili blankets (which use a fiber-optic cable to disperse light over a patient), it is important to remember that the output of various manufacturers’ light bulbs varies widely. By switching from one manufacturer to another, the output can change as much as 50%. This impacts the patient, so always use the same bulbs to ensure consistency. The rating of the output is done in microwatts per square centimeter per nanometer, or mW/sqcm/nm. The output ranges between 6 and 30 mW/sqcm/nm, depending on the manufacturer, so be careful when mixing manufacturers. The clinical results could differ widely, and you will get calls that a device is not working properly when it is. 24×7

Review Questions

1)    Where is the best place to put a temperature sensor on a neonate?
a.    on the thigh
b.    over the liver
c.    on the forehead
d.    over the upper-right lung

2)    What is the light spectrum used for the treatment of bilirubin?
a.    250–275 micrometers
b.    424–475 micrometers
c.    424–475 nanometers
d.    50–75 nanometers

3)    A light bulb with the same part number, voltage, and watts gives off the same light spectrum and power regardless of manufacturer.
a.    True
b.    False

Answers: 1-b, 2-c, 3-b

David Harrington, PhD, director of staff development and training at Technology in Medicine (TiM), Holliston, Mass, is a member of 24×7’s editorial advisory board.

Gary Vogelsang is a TiM BMET assigned to Jordan Hospital in Plymouth, Mass.