IMPROVED CONTROL OF GAS HUMIDITY IN NEONATAL INTENSIVE-CARE VENTILATORS

Difficulties experienced by nursing staff in controlling humidity in n eonatal intensive care ventilators are shown to originate in the use o f a single control, namely a heater, to condition two parameters, name ly temperature and humidity, at the inlet to the inspiratory tube. It is shown that better control can be achieved by separating the gas flo w through the humidifier into two streams, only one of which is humidi fied. It is proposed that the temperature along most of the inspirator y tube should be maintained about 3-5 degrees C higher than the target delivery temperature. This eliminates the risk of condensation in the tube, a second commonly occurring problem in existing systems. It is shown why the control of ventilator systems should be based on absolut e humidity, not relative humidity, even though the latter may be prefe rred for monitoring purposes.