The importance of irradiance and area in neonatal phototherapy.

BACKGROUND: Despite a long period of development, there are still considerable variations in the spectral output, the levels of irradiance, and irradiated area provided by commercial phototherapy systems. These variations depend on the types and output of the lamps used to produce the phototherapy, along with the design of the systems, and principally on whether the phototherapy is provided from overhead or underneath.

OBJECTIVE: To see whether commercially available phototherapy systems produce sufficient irradiance over the surface area of the neonate.

METHODS: Surface plots of the output irradiance were made on a number of systems and used to calculate the effective irradiance on the surface of a premature or term baby, using mapped outlines.

RESULTS: A 10-fold difference in peak central irradiances was found between the systems tested, with a fourfold to fivefold difference in effective irradiance to the baby surfaces. Although work published over 20 years ago showed that levels of irradiance should reach 2 mW/cm2 to achieve optimal effectiveness, some of the commercial systems tested do not appear to achieve this level.

CONCLUSION: Purchasers of neonatal phototherapy systems need to take into account whether the systems will produce sufficient irradiance over the area to ensure maximal effect, to keep the treatment time to a minimum.