Datex-Ohmeda Anesthesia Delivery Unit S/5 Technical Reference Manual page 331

Technical description A-EV1
When the desired tidal volume has been delivered, the inspiration ends. If the preset inspiration time
is reached before the entire tidal volume is delivered, the inspiration is halted and a message to the
User is displayed.
During the Pause phase that follows upon the delivery of the tidal volume, the inspiration, PEEP and
expiration valves are kept closed. The expiration phase starts when the PEEP and expiration valves
are opened.
Figure 6 The inspiration gas flow through the Bellows Block
Pressure controlled ventilation
During the inspiration phase, the inspiration valve opens proportionally to its supplied voltage and
the expiration valve is closed. The PEEP pilot valve acts as resistance for the gas flowing from the
PEEP proportional valve thus creating a pressure on the PEEP valve membrane. The pressure is
controlled by the PEEP proportional valve which is set to a value corresponding to the set pressure
level.
The gas flow from the inspiration valve is set to a value which gives the required rise time (slow/
medium/fast), forces the bellows down thus emptying it into to the patient circuit at the set pressure.
The patient pressure sensor is the feed back element.
In the pressure controlled mode there is no pause and the inspiration valve flow is constant during
the whole inspiration time. If the set pressure level cannot be reached, a message to the user is
displayed.
C-5
Document No. 8502855