VIII THEORY OF OPERATION- cont’d.
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- SYSTEM COMPONENTS
SYSTEM COMPONENTS SYSTEM COMPONENTS
SYSTEM COMPONENTS
SUPPLY GAS INLET FIL
SUPPLY GAS INLET FILSUPPLY GAS INLET FIL
SUPPLY GAS INLET FILTER
TERTER
TER
The supply gas passes through an inlet filter that is located inside the supply gas fitting on the right side of
the ventilator. This filter should be changed periodically as required. It filters particles down to 40
microns. If equipped with entrainment, there is a second filter in the venturi assembly at the inlet in the
rear of the unit.
NOTE: It is recommended that an external filter/water trap be used on the supply gas at all times in order to
provide greater protection to the internal components of the Crossvent.
SUPPLY PRESSURE SENS
SUPPLY PRESSURE SENSSUPPLY PRESSURE SENS
SUPPLY PRESSURE SENSING SWITCH
ING SWITCHING SWITCH
ING SWITCH
A pressure sensitive switch is installed on the gas supply side of the internal pressure regulator. Should the
gas supply pressure to the ventilator drop to a predetermined level, an audible and as well as visual alarm
will occur.
AIRWAY PRESSURE TRAN
AIRWAY PRESSURE TRANAIRWAY PRESSURE TRAN
AIRWAY PRESSURE TRANSDUCER
SDUCERSDUCER
SDUCER
This connects to the proximal airway tube on the circuit through the fitting on the side of the unit. The
pressure transducer converts the pressure signal into an electrical signal. This electrical signal, which
represents the pressure waveform is then used by the CROSSVENT’s microprocessors to accomplish a
multitude of tasks. It is used to sense a pressure drop in the patient breathing circuit created by an
inspiratory effort and then provide a trigger signal to initiate inspiration. The transducer output also
establishes the levels for the all of the pressure related alarms.
DIFFERENTIAL PRESSUR
DIFFERENTIAL PRESSURDIFFERENTIAL PRESSUR
DIFFERENTIAL PRESSURE TRANSDUCER
E TRANSDUCERE TRANSDUCER
E TRANSDUCER
This component is only present if the unit has the optional Exhaled Tidal Volume monitoring feature
installed. It is utilized to measure the pressure drop across an orifice in a pneumotachograph. The
pneumotach (flow sensor) is placed at the proximal airway. As exhaled gas passes through the orifice, it
creates a pressure drop from one side of the orifice to the other. This highly sensitive differential pressure
transducer measures this small pressure difference. The signal from the transducer is then converted by the
microprocessors into a measurement of exhaled tidal volume and minute volume.
MAXIMUM PRESSURE REL
MAXIMUM PRESSURE RELMAXIMUM PRESSURE REL
MAXIMUM PRESSURE RELIEF VALVE
IEF VALVEIEF VALVE
IEF VALVE
This valve vents gas to atmosphere whenever the pressure in the breathing circuit exceeds the preset level of
120 cmH
2
O.
DIAPHRAGM ACT
DIAPHRAGM ACTDIAPHRAGM ACT
DIAPHRAGM ACTUATED RELIEF VALVE (
UATED RELIEF VALVE (UATED RELIEF VALVE (
UATED RELIEF VALVE (D.A.R.V.)
D.A.R.V.)D.A.R.V.)
D.A.R.V.)
This is controlled by the output signal from the Maximum Pressure needle valve (front panel), which is also
applied to the exhalation valve. It sets the relief pressure at approximately the same level as the exhalation
valve.
NEGATIVE PRESSURE RE
NEGATIVE PRESSURE RENEGATIVE PRESSURE RE
NEGATIVE PRESSURE RELIEF VALVE
LIEF VALVELIEF VALVE
LIEF VALVE
This allows gas to enter the breathing circuit whenever a negative pressure greater than approximately 4-5
cmH
2
O is generated. This acts as a failsafe mechanism and in the event of a total system power failure
allows the patient to inhale ambient air.
WARNING: Breathing through this valve requires a greatly increased work of
breathing and only air is provided. A situation in which the patient is breathing
through this valve should be rectified immediately in order to prevent possible
adverse affects to the patient.
WARNING: Should the use of the negative pressure relief valve become necessary,
the operation of the Crossvent in a contaminated environment can be hazardous.
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