General System Overview Product Description
1 - 4 046-004667-00 A7™ Operating Instructions
1.1.3 Fresh Gas Dosing
The A7 fresh gas dosing subsystem offers the following features:
• Virtual on-screen dual flow tube and numerical readouts to display the flows or
concentrations (for electronic flow control system)
• A knob guard to prevent inadvertent movement of the flow control knobs
• Gas supply gauges to indicate the gas pipeline supply pressures and gas cylinder pressures
• Mechanical total flowmeter to display the combined flow of O
2
and Air (for backup flow control
system
)
•An O
2
flush button
• A single auxiliary combined output with O
2
and Air flowmeters
Safety systems within the A7 work to prevent hypoxic mixtures from being delivered to the patient.
Nitrous oxide will not be delivered unless oxygen flow is present. A pneumatic safety system assures
that at least 21% O
2
is present when setting mixtures of O
2
and N
2
O. Additionally, if the A7 is placed
in the Standby mode, O
2
fresh gas flow is not available.
WARNING: When backup flow control system is in use, ensure that both O
2
and air
flow controllers are turned OFF fully at the start and at the end of each
case.
All A7 units are designed to maintain a safe O
2
: N
2
O ratio by allowing nitrous oxide to be set to a flow
rate that is proportional to a previously adjusted flow of oxygen. The N
2
O flow is limited by the flow
of O
2
so that a safe ratio of no less than 21% oxygen can be maintained. The A7 is designed to
maintain oxygen flow at its previously set level when N
2
O is decreased.
1.1.4 Flow Control
Flow Control System and Knob:
The fresh gas flow is electronically controlled by the Electronic Flow Control System (hereinafter
referred to as EFCS). You can set the flow value or O2 concentration value via soft keyboard or knobs.
When the A7 System detects a failure related to the EFCS, the Backup Flow Control System
(hereinafter referred to as BFCS) will be automatically deployed. Two independent flow control knobs
allow setting the input flow rates of Air and O
2
.
O
2
Pressure Loss Alarm:
An O
2
pressure loss alarm announces when oxygen pressure is less than 220 kPa (32 psi).
1.1.4.1 Flow/Pressure Sensing
The breathing system block contains patient flow and pressure sensors to measure inspiratory flow,
expiratory flow, and inspiratory pressure. These sensors enable spirometry and standard pressure and
flow monitoring.
1.1.5 Vaporizer Mounting
The A7 contains a 2-position Selectatec-type vaporizer mounting system to enable anesthetic agents
to be introduced into the fresh gas flow. The mounting system adapts vaporizers with interlock,
which permits only one agent at a time to be administered. Lighting above the vaporizers enables
them to be seen in a dim light environment. Maximum three vaporizers can be mounted at any one
time. The A7 comes standard with a two vaporizer mount. Third vaporizer mount is optional.
Halothane, Enflurane, Isoflurane, Desflurane, and Sevoflurane vaporizers can be used.
Additional, non-functional vaporizer parking spot on the side of the unit is provided as part of the
standard configuration.
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