Evaluation of phototherapy devices used for neonatal hyperbilirubinemia.

OBJECTIVE

To compare phototherapy devices based on their physical and photo-biological characteristics viz spectral properties, maximum and mean irradiance, treatable percentage of body surface area, decay of irradiance over time and in vitro photoisomerisation of bilirubin.

DESIGN

In vitro experimental study.

SETTING

Ocular pharmacy laboratory at a tertiary care hospital. METHODLOGY: All the characteristics were measured at a fixed distance of 35 cm from one compact fluorescent lamp (CFL) and three light emitting diode (LED) phototherapy devices in a dark room with an irradiance of <0.1uW/cm2/nm. Estimation of products of in vitro photoisomerisation was done using liquid chromatography - tandem mass spectroscopy (LC-MS/MS).

RESULTS

The emission spectral data were comparable between the phototherapy devices. The devices, however, differed in their maximum irradiance with the spot and indigenous LED units having the highest and lowest values, respectively (56.5 and 16.8uW/cm2/nm). The mean irradiance measured in 5x5cm grids falling within the silhouette of a term baby of the spot and improvised LED devices were low (26.8uW/cm2/nm and 11.5uW/cm2/nm, respectively) possibly due to unevenness in the irradiance of light falling within the silhouette. There was a significant difference in the amount of bilirubin left after exposure to light over a 2hour time period (% reduction of bilirubin) among the four devices (P=0.001); at 120 minutes after exposure, the amount of bilirubin left was lowest for the CFL (16%) and spot LED (17%) devices and highest for the indigenous LED unit (41%).

CONCLUSIONS

The four phototherapy devices differed markedly in their physical and photobiological characteristics. Since the efficacy of a device is dependent not only on the maximum irradiance but also on the mean irradiance, rate of decay of irradiance, and treatable surface area of the foot print of light, each phototherapy device should have these parameters verified and confirmed before being launched for widespread use.