S
ECTION
Theory of operation
This chapter details the operational theory of the 700 Series Ventilator System. It
begins by describing the overall operation of the ventilator and continues by
describing the pneumatic system, including the individual components and their
operations as subsystems. Next it describes the electrical system, including the
operations of the printed circuit boards (PCBs). Finally it describes the interactions
between all ventilator components during breath delivery and under certain
other conditions.
2.1 Overview of ventilator operation
The 700 Series Ventilator System (Figure 2-1) consists of two major systems: the
pneumatic system and the electrical system. The pneumatic system, under control
of the breath delivery (BD) microprocessor, supplies air and oxygen to the patient
system external to the ventilator. The electrical system powers the ventilator and
provides electronic control of the ventilator’s components. It includes five printed
circuit boards (PCBs), a power supply, and various minor components (fans,
harnesses, etc.).
Room air and oxygen from an external supply enter the cylinder via the mixing
manifold. The piston/cylinder assembly, which is driven by the motor, mixes the
gases and precisely controls the flow to the patient. An important aspect of the
piston-based pneumatic system is that no contact occurs between the piston and
cylinder wall; there is a minute gap. Because the piston and cylinder do not touch,
friction between the piston and cylinder is eliminated, improving the ventilator’s
performance and reducing wear on the parts.
The output mixture of air and oxygen passes through the inspiration manifold
and a patient system external to the ventilator; this patient system may be
composed of tubing, filters, water traps, and a humidification device. The patient
exhales the gas through the opened exhalation valve.
Pressure transducers provide feedback measurements to the BD microprocessor.
After undergoing digital conversion, these measurements are used in calculations
that control ventilation.
Summary of Contents for Puritan Bennett 700 Series
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