Introduction Theory of Operation
1 - 2 046-006272-00 A7â„¢ Service Manual
1.1 Introduction
The A7 Anesthesia System is a simple and convenient anesthetic gas delivery system that produces
anesthesia gas and controls delivery of anesthesia gas by using a configured vaporizer. It supports
automatic and manual ventilation. It can also monitor various parameters of patients, such as the
airway pressure, inspired tidal volume and expired tidal volume.
The A7 Anesthesia System provides the following ventilation modes:
• Volume Control Ventilation (VCV), which includes the Pressure Limit Ventilation (PLV) function
• Pressure Control Ventilation (PCV) with/without the Volume Guarantee (VG) ventilation mode
• Synchronized Intermittent Mandatory Ventilation (SIMV) with the VC mode
• SIMV with the PC mode
• Pressure Support (PS) ventilation mode
• Spontaneous ventilation in Manual mode with the Airway Pressure Limit (APL) fully open
• Manual Ventilation through the use of a breathing bag
• Electronic Positive End Expiratory Pressure (PEEP) is available in all ventilation modes. Control over
inspiratory flow (Tslope) is possible in PCV, SIMV, and PS modes. Automatic fresh gas
compensation helps patients suffer less from manual changes in fresh gas flow rate. The
traditional bellows system is driven by gas and makes patient ventilation clearly visible.
The A7 fresh gas electronic flow metering system inherits the features of a traditional anesthesia
system and moreover is enhanced in ease of use. The dual-tube electronic flow meter displays more
precise readouts. A knob guard prevents inadvertent movement of the flow control knobs. Gas
supply gauges indicate the pipeline and cylinder gas supply pressures in real time. An auxiliary O2
flow meter is placed on the upper left to make it convenient to read the O2 flow rate. The O2 flush
button is in the traditional position near the front left corner of the table top.
Safety systems within the A7 work to prevent hypoxic mixtures from being delivered to the patient.
Nitrous oxide will not be delivered unless oxygen pressure is present.
The heating system of the A7 patient breathing circuit minimizes condensed water and sends warm
and humidified gas back to the patient. The pressure gauge, APL valve and manual breathing bag of
the patient breathing circuit support fast plug and unplug to facilitate their installation and
maintenance. The APL valve has a rotary knob that provides a clear view of the manual breathing
pressure setting. The sodalime absorber canister can be opened and closed quickly through a handle.
It can absorb sodalime in standard Pre-paks or loose-fill sodalime. A drainage valve is configured for
the sodalime absorber canister.
Two flow sensors are configured on the patient breathing circuit to monitor the flow of inspired and
expired gases and monitor the airway pressure. The operator can rotate and fix the patient breathing
circuit as required. In addition, the patient breathing circuit is equipped with a side plug for gas
leakage detection. The Anesthesia Gas Scavenging System (AGSS) connectors are at the rear of the
A7.
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