Spectral Power and Phototherapy

I place orders for my newborn patients to receive phototherapy treatment for jaundice so often that I tend not to really think about how phototherapy works unless a problem develops. It’s only when I have a patient whose indirect bilirubin level fails to decrease (or continues to rise) under phototherapy that I start to ask the following questions:

• Are the phototherapy lights and/or blankets I ordered actually working? Is there some sort of equipment or mechanical issue?
• Am I using enough phototherapy light? Do I need to add another overhead light or bili-blanket?
• What is the total irradiance being given?
• Are the lights positioned close enough to my patient, or are they too far away?
• Does the infant have enough skin exposed while getting phototherapy?
• Is my patient coming out from phototherapy too often? How often has he or she been out for phototherapy “breaks” to bond and breastfeed?
• Is there some underlying hemolytic disorder that I am missing, such as G6PD deficiency or a minor blood group incompatibility?

All of us who medically care for newborns are familiar with the 2004 clinical practice guideline from the American Academy of Pediatrics (AAP) called “Management of Hyperbilirubinemia in the Newborn Infant 35 or More Weeks of Gestation.”[1] This landmark publication includes recommendations for when to initiate phototherapy and consider doing an exchange transfusion in newborns via a nomogram that factors in hours of life and the presence or absence of “risk factors” for severe jaundice.  It was not until recently that I learned that Appendix 2 of this practice guideline paper dives into of the factors that affect the “dose” and efficacy of phototherapy. Based on this document, the main factors in phototherapy efficacy are the following:

1. Spectrum of light emitted: blue-green light between 430-490 nm is the most effective
2. Irradiance: per this paper, standard is 8-0 µW/cm2 per nm and intensive is > 30 µW/cm2 per nm
3. Surface area of the baby that is exposed to light during treatment and distance of light to patient
4. The underlying etiology of jaundice
5. Total serum bilirubin level when phototherapy is initiated

Of these five factors, the only two that are really modifiable to any extent are light irradiance and surface area. In order to optimize phototherapy, one needs to increase irradiance and/or increase an infant’s body surface area exposed to lights.  Thus, we can think of phototherapy strength, or “spectral power,” as the product of irradiance and body surface area.

Spectral power = light irradiance x surface area

The importance of spectral power is highlighted in the 2004 AAP guidelines: “Intensive phototherapy implies the use of high levels of irradiance in the 430-490-nm band delivered to as much of the infant’s surface area as possible.”

Over the last two decades, there has been a definite shift towards using increasingly higher irradiances for “intensive phototherapy” in newborn medicine.  I’ve worked in multiple NICUs and have seen irradiance levels of up to 60-70 µW/cm2 per nm utilized in severe cases of hemolytic jaundice to prevent the need for a double-volume exchange transfusion. Intermittent (cycled) phototherapy[2], which has been gaining acceptance in newborn medicine, often utilizes higher than typical irradiances as well.

The AAP recommends that phototherapy lights be placed as close to an infant as possible, ideally within 10 cm. This is because the proximity of an infant to lights affects irradiance – the shorter the distance from lights to an infant, the higher the irradiance and spectral power of the phototherapy being used.

Spectral power is also increased by increasing the body surface area that is exposed to phototherapy. Current methods of increasing an infant’s body surface area include using both overhead lights and placing them on fiber optic phototherapy pads simultaneously, removing babies’ diapers while under lights, and/or lining their basinets with either white sheets or aluminum foil while getting phototherapy treatment. Utilizing extra equipment to increase body surface area during phototherapy can be burdensome and time-consuming for NICU nurses and staff, and also make it more difficult for an infant to come in and out of phototherapy.

NeoLight’s Skylife Neonatal Phototherapy System, designed for both hospital and home use, has the highest spectral power on the market. Skylife’s best-in-class spectral power is accomplished via the following unique features:

1. Three levels of irradiance:
   - Low: 30 ± 5 µW/cm2/nm
   - High: 45 ± 10 µW/cm2/nm
   - Very High: > 55 µW/cm2/nm
2. Minimum Light Distance: Has an under-baby system in which infants lie on top of phototherapy lights covered with a GelMat for comfort = significant decrease in light distance  
3. Large Surface Area: Unit has a large, irradiated surface area of 199 in2 (769 cm2), optimizing surface area via a “3D light array.” This creates 40% body surface coverage with effective and uniform light.

With adoption of phototherapy systems like the Skylife Neonatal Phototherapy System, which have best in class spectral power, I anticipate that my newborn medicine colleagues and I will spend less time having to do phototherapy “troubleshooting,” and appreciate a significant reduction on our jaundiced patients’ hospital lengths of stay. In addition, there is no need for extra phototherapy equipment, such as overhead lights, biliblankets, or white sheets to increase surface area, when the Skylife is used. These savings in time, equipment, and duration of hospital admission are a win-win situation for medical providers, patients, and their families.