The Breathing System Theory of Operation
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1.5 The Breathing System
1.5.1 Brief Introduction
The A7 breathing system supports three operating modes: mechanical ventilation, manual
ventilation, and standby. These modes allow the operator to apply proper ventilation strategies
based on the patient's needs.
The types of flow paths through the breathing system vary with the operating mode or status.
1.5.2 Automatic Mode, Inspiration
When the Auto/Manual switch is positioned at Auto, the system closes the manual ventilation path.
Drive gas pushes down on the bellows. Gas flows from the bellows, through the CO2 absorber
canister, and through the inspiratory check valve to the patient.
During inspiration, fresh gas flows into the inspiratory limb, upstream of the inspiratory check valve.
In volume mode, tidal volume is compensated for variations in fresh gas flow to ensure that the
volume delivered to the patient meets the set value.
In pressure mode, the inspiratory pressure is regulated both in gas flow and airway pressure to ensure
the airway pressure is held at the set inspiratory pressure during the patient inspiration.
FIGURE 1-51 Automatic Mode, Inspiration Diagram