Assembling patient circuits
Connecting a double limb circuit (Astral 150 only)
The Astral device measures exhaled air flowing through the double limb circuit adapter. This enables
patient-exhaled tidal volume to be accurately measured and monitored.
To connect a double limb circuit:
1. Ensure the device is fitted with the double limb adapter (otherwise change the adapter).
2. Connect the ends of the air tubing to the inspiratory and adapter ports on the device.
3. Attach any required circuit accessories (eg, humidifier or filter).
4. Select the circuit type and perform a Learn Circuit.
5. Attach a patient interface (eg, mask) to the end of the air tubing.
Learn Circuit
In order to support a wide range of circuit configurations and accessories, the Astral device provides a
Learn Circuit function to determine the characteristics of the circuit. As part of the Learn Circuit
functionality the Astral performs a device self-test.
CAUTION
To ensure optimum and accurate performance, it is recommended that the Learn Circuit function
be performed with every change of circuit configuration and at regular intervals not less than once
every three months.
Do not connect patient interfaces prior to performing the Learn Circuit. Patient interfaces include any
components placed after the single circuit's expiratory valve or exhalation port, or double limb circuit's 'Y'
piece (eg, HMEF, catheter mount, mask, tracheostomy tube).
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