A new device for 100 per cent humidification of inspired air

A new humidifier for use during mechanical ventilation in
endotracheally intubated patients is described and tested. The humidifier is
based on a heat-moisture exchanger, which absorbs the expired heat and moisture
and releases it into the inspired air. External heat and water are then added
at the patient side of the heat-moisture exchanger, so that the inspired gas
should reach 100% humidity (44 mg/l) at 37°C. In bench tests using constant
and decelerating inspiratory flow and minute volumes of 3–25 l the device gave
an absolute humidity of 41–44 mg/l, and it reduced the amount of water consumed
in eight mechanically ventilated patients compared with a conventional active
humidifier. During a 24-h test period there was no water condensation in the
ventilator tubing with the new device.