1. Therapeutic & Prosthetic equipment I
Lecture (4)

2. Humidity
The losses of water for premature newborns, with 25 weeks of gestation, treaties in ambient with relative humidity in 20 %, exceed 200 ml/kg/day.
The increase of the relative humidity inside newborn incubator reduced the loss of water for the skin of the premature newborns

3. In the first days of life, the daily evaporative loss from premature newborn can reach up to 20% of body mass.
Such loss can be reduced by increasing the air humidity inside the incubator.

4. The humidity control system of the newborn incubator can be presented under two aspects:
1) Active humidity control system
This system is formed by an ultrasonic vaporizer, in which, the vapor is controlled for a control system that has a humidity sensor, what it causes a control of closed mesh.
The relative humidity of air is measured and compared with a value of reference and this difference it is used as way of control.

5. 2) Passive humidity control system
This system consists of a reservoir with water whose surface is crossed on the part of the air flow generated for weathercock.
A greater or minor humidity of air can be gotten regulating the air flow.

6. Incubator components 1-air filter, 2-air flow, 3-weathercock,
4-heater element,
5-mattress,
6-water reservoir.

7. Incubator: Principles of work
The mattress where the baby lies is completely enclosed by a clear plastic canopy.
In this temperature and humidity are the parameters which have to be controlled .
The temperature in the incubator is increased by a heater element below the mattress.

8. A motor driven fan near the heater draws in fresh air through a filter and blows it past the heater, warming the air.
The air is directed up through slots into the area above the mattress and circulated around.
A threshold value for temperature and humidity is set manually by using the potentiometer.

9. The air temperature is monitored by temperature sensors and is adjusted by controlling the current to the heater.
The user can set the incubator to control the temperature of the air.
If the temperature of the incubator increased above the threshold value then the alarm will beep and the fan will be on and it remains on till the temperature decreased to the threshold value.

10. If the temperature of the incubator decreased below the threshold value then also the alarm will beep and the heater will be on and it remains on till the temperature increased to the threshold value.
Supplementary oxygen can be taken in by an oxygen inlet connection where it is mixed with the fresh air through the filter.
The humidity can be increased by the use of water baths or by dripping water on a heated element.
Light bulbs heat air in the bottom part of the incubator.
The air passes over a container with evaporating water, so that its humidity increases.