Covidien Newport e360, Руководство по обслуживанию

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Theory of Operations
A-12 Service Manual
The regulated gas enters the PSOL valves, which are designed to supply gas to the patient circuit at
the preset or ventilator managed flow. A PSOL valve calibration creates a lookup table of the
currents required to generate the range of flows from the PSOL valve. The lookup table allows the
ventilator to target the required flow as quickly as possible, and feedback from the flow sensor every
10 milliseconds allows the ventilator to refine flow delivery.
Because the lookup table is unique to each combination of regulator and PSOL valve, the PSOL
valve calibration should be rerun when either component is replaced. Most of the gas pressure
drops across the PSOL valves, and gas exiting the PSOL valves is close to patient pressure.
Check valves downstream of the PSOL valves prevent cross- contamination from the ventilator to
the gas supplies.
The flow sensors are hot wire anemometers: as gas flows through the sensor, it cools the wire and
increases its resistance. The flow sensor adjusts power to keep wire temperature constant, and the
power required is directly proportional to the flow across the wire. Each flow sensor is factory-
calibrated for air or oxygen.
Air and oxygen then enter the mixing chamber, where they are combined. The blended gas then
exits to the patient circuit through the inspiratory manifold. The inspiratory manifold also includes
the emergency intake valve and the emergency relief valve. These components are described in
section
A.5 .
The oxygen sensor is mounted directly to the inspiratory manifold where it can monitor the
delivered FiO
2
and compare it to the set FiO
2
. Because the oxygen sensor is sensitive to changes in
atmospheric pressure and temperature, the ventilator calibrates the oxygen sensor, each time the
O
2
3 min button is activated and any time the monitored FiO
2
is greater than +0.07 from the set
value. Ventilator software assigns an FiO
2
of 1.0 to the voltage read during calibration. The user may
also initiate a calibration from a menu on the GUI.
During exhalation, the inhalation system supplies a bias flow of 3 L/min through the patient circuit
to flush exhaled CO
2
and stabilize temperature, humidity, and baseline pressure. When either Leak
Compensation or Non Invasive is turned on, the ventilator provides leak compensation by increasing
flow above bias flow to maintain end expiratory flow near 3 L/min in the expiratory flow sensor. The
maximum leak compensation level available when
Leak Compensation is turned on varies for each
patient category as follows: ped/infant = 8 L/min, adult = 15 L/min. Maximum leak compensation
supplied by the
Non Invasive function is 25 L/min.
Transducers monitor pressure in the inspiratory manifold and expiratory system. A transducer
rezero solenoid maintains an accurate zero point for the pressure transducers by opening
periodically to note the voltage that equals atmospheric (zero) pressure.
A.6.2
Exhalation System
The exhalation system measures the flows and volumes of gas exhaled from the patient circuit,
measures pressure, and controls the exhalation valve to manage pressure in the breathing circuit
and allow patient exhalation.