Chapter 3
Theory of Operation
REF 580-1000-02 G
Esprit® Ventilator Service Manual © Respironics, Inc.
3-7
Inspiratory Pressure
Transducer Solenoid
(SOL4)
The inspiratory pressure transducer solenoid periodically vents the
inspiratory pressure transducer to atmosphere and makes a
measurement at zero (atmospheric) pressure. Periodically autozeroing
the transducer allows it to correct the slight zero voltage drift that can
occur over time, and improves the overall accuracy of the pressure
measurement.
During normal operation, SOL4 is de-energized and applies patient
circuit pressure to the inspiratory pressure transducer. During an
autozero, SOL4 is energized, venting the transducer to atmosphere.
This occurs during power on self test (POST), at the beginning of a
breath one minute after POST, six minutes after POST, eleven minutes
after POST, and hourly thereafter.
Exhalation System
The exhalation system maintains circuit pressure and conditions, filters,
and monitors exhaled gas. It contains the heated exhalation filter (F3),
exhalation pressure transducer (PT2), exhalation pressure transducer
solenoid (SOL3), exhalation valve (EV), exhalation non-rebreathing
check valve (CV4), and the exhalation flow sensor (FS3).
Heated Exhalation
Filter (F3)
The heated exhalation filter includes a heated filter sleeve and a
bacteria filter. The heater protects the exhalation flow sensor and
exhalation system components from condensation by heating exhaled
gas (which has cooled in the exhalation limb) above the dew point.
The exhalation bacteria filter protects the exhalation flow sensor and
exhalation system component from contaminants and filters exhaled
gas before it is vented to atmosphere.
Exhalation Pressure
Transducer (PT2)
The exhalation pressure transducer on the sensor PCB measures patient
circuit pressure from the exhalation side of the patient circuit. During
normal operation PT2 is the primary transducer for measuring patient
pressures, including peak inspiratory pressure (PIP), mean airway
pressure (MAP), end inspiratory pressure, and auto-PEEP. The
exhalation pressure transducer provides monitoring data for closed loop
control.
Exhalation Pressure
Transducer Solenoid
(SOL3)
The exhalation pressure transducer solenoid periodically vents the
exhalation pressure transducer to atmosphere and makes a
measurement at zero (atmospheric) pressure. Periodically autozeroing
the transducer allows it to correct the slight zero voltage drift that can
occur over time, and improves the overall accuracy of the pressure
measurement.
During normal operation, SOL 3 is de-energized and applies patient
circuit pressure to the exhalation pressure transducer. During an
autozero, SOL3 is energized, venting the transducer to atmosphere.
This occurs during POST, at the beginning of a breath one minute after
POST, six minutes after POST, eleven minutes after POST, and hourly
thereafter.
Delivery System Components
