Conventional continuous flow anesthesia machines include an oxygen flush function for quickly filling the circle system and for quickly removing anesthetic agent and elevating the oxygen percentage in the breathing circuit. The flush is activated by a non-locking button with a self-closing valve that when pressed supplies pure oxygen to the common gas outlet of the anesthesia machine. The flow of about 35 – 75 L/ min, depending on the machine, at a pressure of about 400 kPa bypasses the flowmeters and the vaporizers. The button is recessed in a housing to prevent accidental depression.

Example of an oxygen flush button on a continuous flow anesthesia machine

The flush function described above is not well suited for a demand flow system such as the UAM and is wasteful where there is a limited supply of oxygen. Furthermore, with a concentrator-based system, when electrical power is lost and there is no external high pressure source of oxygen, the user may end up giving less oxygen to the patient, believing that they are giving more, because the reserve becomes exhausted quickly. The flush then becomes a hazard as it has become non-functioning and can confuse the user about what to do next. There is no ISO requirement for flush in a demand flow system.

Because of the UAM’s low volume characteristics it only takes a few vigorous pumps of the bellows to quickly expel anesthetic agents and carrier gases out of the UAM’s breathing circuit.

Procedure for flushing anesthetic gases and agents from the UAM’s breathing circuit

If you need to quickly flush anesthetic agent or carrier gas from the breathing circuit, perform these steps:

1. Disconnect the Y piece from the patient
2. Turn off the vaporizer completely to prevent drawing any agent through the system.
3. Turn the oxygen flow to maximum.
4. If the UAM is fitted with a ventilator, move the bellows cut off handle to the Bellows position (front)
5. Activate the manual bellows up and down with long strokes 7-8 times while blocking the Y piece with your thumb or palm of your hand.
6. If the UAM has a ventilators move the bellows cut off handle to the Ventilator position (back).
7. Operate the ventilator in volume mode for two or three cycles with a tidal  volume of 500 ml or more.
8. Connect the patient to Y piece and continue the case with the appropriate UAM and ventilator settings.