Theory of operation
2-32
10070389 Rev. A
Puritan Bennett™ 700 Series Ventilator System Service Manual
2.2.6 PEEP/CPAP system
The PEEP/CPAP system, shown in Figure 2-19 and Figure 2-20, regulates pressure to the
exhalation valve as required to maintain PEEP/CPAP during exhalation.
Figure 2-19. PEEP/CPAP system pneumatic diagram
2.2.6.1 Component descriptions
The PEEP/CPAP system includes these components; these are shown in Figure 2-21.
• The
filter
removes particles of 0.3
μ
m nominal from the air to be compressed by the PEEP
pump.
• The
PEEP reservoir
has three chambers. Air is drawn into the chamber 1, and from there
into the PEEP pump. This chamber reduces pump noise. Air compressed by the pump is
then forced into chamber 2, which reduces pressure fluctuations. Air exits chamber 2
through a jet venturi, which drops the pressure to the desired PEEP/CPAP pilot pressure.
Chamber 3 acts like a capacitor, reducing pressure fluctuations and preventing PEEP
undershoot.
• The
PEEP pump
, a vibrating-armature pump, generates PEEP/CPAP pilot pressure. Gas
compressed by the PEEP pump fills a reservoir. The pump is controlled by pulse-width
modulating the pump drive voltage.
2.2.6.2 System operation
If PEEP is selected, the pump is turned on, drawing room air through the filter, into the
reservoir, and toward the pump. The pump compresses the air as required to supply PEEP
requirements. The compressed gas is then drawn into a separate chamber of the reservoir.
This gas exits through a jet venturi, which reduces the pressure to the desired PEEP/CPAP pilot
pressure. It then enters a final chamber, which provides further damping of pressure
oscillations. During exhalation, the gas flows through the de-energized exhalation solenoid,
which pilots the exhalation valve open as required. During inspiration, the pump remains on,
but the exhalation valve is piloted by the inspiratory pressure, not PEEP pilot pressure.
PEEP pump
Filter
7-00110
To
exhalation
system
Jet venturi
Restrictor
PEEP reservoir
Summary of Contents for Puritan Bennett 700 Series
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