Most CNS people have phototherapy while in bed at night. In the past jaundiced newborns had phototherapy lights above them and overhead lights remain the phototherapy system most commonly used by CNS people. Overhead systems are the simplest to build and expand as a child grows.
More recently some newborn phototherapy has been developed with the light source under the child. Similar underneath systems have been developed for CNS people, involving the user sleeping on a translucent, tensioned net with the lighting source under the net. The choice of netting and the tensioning devices makes this system more complex than overhead systems.
Effectiveness of Night Phototherapy
The extent to which night phototherapy systems meet effectiveness criteria may be considered as follows:
1. Typical overhead lights use ten longitudinally arranged 4 ft (1200 mm) fluorescent tubes for a total energy input of 360 watts. Alternatively twenty transversely arranged 2 ft. (600mm) tubes may be used with the same wattage input. Underneath systems using fluorescent tubes typically have similar wattage inputs.
2. Overhead systems must allow for the user to turn over in sleep without hitting the lights. For a small child the distance from the skin to the lights is usually about 8 to 10 inches (200-250 mm). As a CNS person grows the distance required must increase to 12-14 inches (300 350 mm) or more. Because of the relatively large distance involved, a large amount of the wattage input generates light that is wasted by being absorbed by other surfaces or by disappearing generally into a room. Worse, as the user grows the distance and effectiveness of overhead lights decreases at a time when the user requires more, not less, phototherapy.
3. A major benefit of underneath systems is that they typically have the light source only about 4 inches (100 mm) from the skin that is in touch with the netting. Because of the skin to light source distance, well designed underneath lights are potentially significantly more effective than overhead.
4. The energy lost through acrylic screens is a small factor for overhead lights. For underneath lights the netting bed is estimated to absorb an additional 15% of the light energy. Proponents of underneath systems consider that, compared with overhead systems, the proximity of the light source to the skin more than compensates for this loss. If this is the case it implies that the loss caused by overhead lights being about 12 inches (300mm) from the skin is significantly more than 15%.
5. A fundamental limitation on the effectiveness of both night phototherapy systems is that they provide light to only one side of the body at a time. This is referred to as single-sided phototherapy. Skin directly irradiated is only about 35% of body surface area. With some surrounding reflecting surfaces, perhaps another 10% of body surface may receive some irradiation, but at intensity that is a small fraction of the direct radiation.
6. Deterioration in the light output of fluorescent tubes is a major practical factor in the effectiveness of phototherapy. The cost of a changeover of the special fluorescent tubes may be several hundred dollars depending on tube prices in the geographical location involved. For people having 10 hours of phototherapy each night, tubes are typically changed after 1000 to 1200 hours of use or every 3 to 4 months. Just prior to changing tubes their effectiveness has been reduced by 35%. This means that, if 8 hours phototherapy per night is required with new tubes, over 12 hours is required for tubes just before changeover, otherwise blood bilirubin levels will increase.
7. Both night phototherapy systems cause substantial lifestyle problems for the user and the family. For overhead systems the CNS person has to sleep naked and uncovered. The room, which cannot reasonably be shared, must be kept warm and draft free. Dehydration can be a problem. Many children do not sleep well under intense blue lights and feel insecure without covering. Underneath systems do allow the user to have bed covering, however some find many hours on a stretched netting bed uncomfortable.
8. As a child grows to adolescence and adulthood a number of factors (including skin thickening and increase in the ratio of body mass to body surface area) cause the required amount of phototherapy to increase. Concurrently the CNS person is progressively sleeping less. A child may sleep for 12 hours, but most adolescents and adults sleep for 8 hours or less. Thus, at a time when more phototherapy time is required, time available for night phototherapy while asleep is decreasing substantially. In this circumstance a significant part of the required phototherapy time required will need to be while the person is lying in bed, but awake. For most people this is unacceptable.
9. While sleeping under or over intense blue lights may be acceptable for children, serious lifestyle problems arise for late teens and adults who aspire to no longer sleep alone. Understandably, for the vast majority of these people, night phototherapy is totally unacceptable.
10. People with the most serious forms of CNS may require 12 hours of night phototherapy and still have blood bilirubin levels that are high and approaching the dangerous level. Blood bilirubin levels are known to increase when CNS people have other illnesses or accidents causing a greater need for phototherapy, With 12 hours per day already being used, the safety factor to reduce bilirubin is relatively low and certainly involves phototherapy while awake.
In summary, night phototherapy is appropriate
and reasonably acceptable for small children. As CNS people grow
and get closer to adulthood, phototherapy while asleep becomes
both less effective and less acceptable. Bilirubin
levels rise and, without some alternative to night phototherapy,
many people with the more serious forms of CNS must contemplate
a liver transplant.
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