Two matched groups of Chinese infants with "idiopathic" jaundice were subjected to phototherapy, one group to "single-direction" phototherapy and the other to "double-direction" phototherapy. The total energy output on the skin of the infants was similar in both groups. The 24hour fall in bilirubin levels was almost identical in the two groups; the number of infants in each group achieving bilirubin levels less than 11 mg/100 ml at 24, 48, and 72 hours was statistically very similar too. Where the energy output can be adjusted to supply a constant dose on the infant (by varying the energy output in inverse proportion to the skin area exposed), the effect of varying the skin area under phototherapy is minimal. However, the total area of skin exposed to phototherapy under uniform lighting conditions is important because it determines the dose of energy output acting on it, and hence the effectiveness of the procedure.
K. L. Tan (Wed,) studied this question.