Theory of operation
2-72
10070389 Rev. A
Puritan Bennett™ 700 Series Ventilator System Service Manual
If the high-flow solenoid is chosen, this solenoid is energized during the first part of the
retraction period. Oxygen flows through the high-low orifice at 150 L/min, through the
manifold, and into the cylinder (which is retracting at a minimum of 150 L/min). During the
second part of the retraction period, the oxygen solenoid is de-energized, and only room air
flows into the cylinder as the piston retracts.
If the low-flow solenoid is chosen, this solenoid is energized during the first part of the
retraction period. Oxygen flows through the low-flow orifice at 15 L/min, through the
manifold, and into the cylinder. Because the piston is retracting at a minimum of 150 L/min,
room air simultaneously flows through the manifold and into the cylinder to augment the
low oxygen flow. During the second part of the retraction period, the oxygen solenoid is de-
energized, and only room air flows into the cylinder as the piston retracts.
If 100% oxygen is selected, the high-flow solenoid is energized during the entire retraction
period. Oxygen flows through the high-flow orifice at 150 L/min, and room air does not enter
the cylinder.
2.6.4.3 Mandatory breathing with delivered volumes less than 250 ml
In mandatory breathing, when the volume of gas being delivered is less than 250 mL (a
combination of base flow and leak compensation), the piston may not retract with each
breath. Because the cylinder holds enough gas to deliver more than one such breath, the
piston makes a small excursion forward to deliver a breath, retracts to the PEEP level, then
makes another small excursion forward to deliver another breath. (See Figure 2-62). It only
retracts completely for filling when insufficient gas remains to deliver the next breath.
Summary of Contents for Puritan Bennett 700 Series
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