Introduction Theory of Operation
1 - 2 046-001141-00 A5/A3â„¢ Service Manual
1.1 Introduction
The A5/A3 Anesthesia System is a continuous flow inhalation gas anesthesia system that delivers
anesthetic vapor, and provides for automatic and manual modes of ventilation. It is equipped with a
monitoring system for ventilation, inspired, and expired gas. The A5/A3 is intended for use in
operating rooms. It will be used with O2, N2O, and AIR supplied by a medical gas pipeline system or
by externally mounted gas cylinders. Anesthetic agents can be delivered via vaporizers mounted on
the machine.
The A5 ventilator provides the following ventilation modes:
• Volume Control Ventilation (VCV), which includes the Pressure Limit Ventilation (PLV) function
• Pressure Control Ventilation (PCV) with/without Volume Guarantee (VG) ventilation mode
• Synchronized Intermittent Mandatory Ventilation (SIMV) with VC mode
• Synchronized Intermittent Mandatory Ventilation (SIMV) with PC mode
• Pressure Support (PS) ventilation mode
• Spontaneous ventilation in Manual mode with APL fully open
• Manual ventilation through the use of a breathing bag
The A3 ventilator provides the following ventilation modes:
• Volume Control Ventilation (VCV), which includes the Pressure Limit Ventilation (PLV) function
• Pressure Control Ventilation (PCV)
• Synchronized Intermittent Mandatory Ventilation (SIMV) with VC mode
• Pressure Support (PS) ventilation mode
• Spontaneous ventilation in Manual mode with APL fully open
• Manual ventilation through the use of a breathing bag
Electronic PEEP is available in all ventilation modes. User control over inspiratory flow (Tslope) is
possible in PCV, SIMV, and PS modes. Automatic fresh gas compensation limits the effect on the
patient ventilation from changes in fresh gas flow rate by the operator. The traditional bellows system
is driven by oxygen and makes patient disconnections clearly visible.
The A5/A3 fresh gas dosing subsystem offers the ease of use and features of a traditional anesthesia
system. The dual-flow tubes electronic flowmeter, which includes redundant numerical readouts,
displays the O2, N2O, and Air flows at all times. A knob guard prevents inadvertent movement of the
flow control knobs. Gas supply gauges and auxiliary O2/Air flowmeters with blended output indicate
the gas pipeline supply pressures and gas cylinder pressures. An auxiliary O2 flowmeter is placed at a
convenient location for the operator. The O2 flush button is in the traditional location near the front
left corner of the table top.
Safety systems within the A5/A3 work to prevent hypoxic mixtures from being delivered to the
patient. Nitrous oxide will not be delivered unless oxygen pressure is present. A pneumatic safety
system assures that at least 21% O2 is present when setting mixtures of O2 and N2O.
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