Chapter 3
3-8
Esprit® Ventilator Service Manual © Respironics, Inc.
REF 580-1000-02 G
Theory of Operation
Exhalation Non-
rebreathing Check
Valve (CV4)
The exhalation non-rebreathing check valve prevents the patient from
inspiring room air through the exhalation limb of the patient circuit.
During normal operation, it blocks the exhalation system from
atmosphere, allowing the patient to trigger a breath.
Exhalation Valve (EV)
The exhalation valve assembly is a stepper motor-controlled valve. At
the beginning of an inspiration, the exhalation valve shuts to create a
closed circuit and allow the patient system to pressurize. The exhalation
valve opens at the beginning of exhalation, allowing system pressure to
vent to atmosphere.
The exhalation valve also regulates positive end expiratory pressure
(PEEP) and expiratory positive airway pressure (EPAP) levels during
exhalation.
Exhalation Flow
Sensor (FS3)
The exhalation flow sensor measures the flow leaving the ventilator. This
flow includes gas exhaled by the patient, tubing compliance volume,
and bias flow if flow triggering or Auto-Trak triggering is selected. The
ventilator uses the exhaled flow measurement to compute flow and
volume coming from the patient and the circuit.
A thermistor in the flow sensor measures the temperature of the gas and
provides the microprocessor with information to compensate the
measured flow.
Delivery System Components
