Covidien Newport e360, Service Manual

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Description of Functional Subsystems
Service Manual A-13
Figure A-7. Ventilator Exhalation System
Because gas delivered to and exhaled from the patient is humidified to near 100% relative humidity,
the expiratory block includes a heater to prevent condensate from forming as the exhaled gas
passes through the exhalation system.
The heater heats the expiratory block and flow sensor to prevent condensation. The exhalation flow
sensor includes a hot wire sensor and a temperature compensation wire. By measuring the
temperature exchange for the hot wire in the flow sensor the ventilator calculates the flow of the
exhaled gas. The exhalation flow sensor requires a short calibration before it is put into use. The
calibration is performed by the user at ventilator startup and may also be initiated by the user during
ventilation if calibration is suspect.
Gas from the exhalation valve flows to the exhalation flow sensor. The exhalation valve includes a
flexible silicone exhalation diaphragm, and drive pressure from the jet pump opens and closes the
diaphragm to manage pressure in the breathing circuit and allow patient exhalation.
The exhalation solenoid is a small PSOL valve that controls pressure to the exhalation valve
diaphragm by varying its outlet size. Gas from the exhalation solenoid enters the jet pump, where
it flows through a jet nozzle to create drive pressure to the exhalation valve diaphragm. The low
mass of the jet pump allows it to operate without the complications caused by oscillation of a larger
part.
A pressure transducer at the exhalation valve provides feedback that tells the exhalation solenoid
to increase or decrease its output to achieve the correct drive pressure. The exhalation solenoid
associates an approximate PEEP with an approximate drive pressure. In case of a circuit disconnect,
these reference pressures help avoid supplying excess pressure in the circuit after reconnection.
Excess flow from the jet pump vents through the muffler.
1 Drive pressure sensor 4 Machine pressure 2 sensors
2 Exhalation PSOL valve 5 Rezero valve machine 2
3 Muffler