Philips V200 - Manual (Page 142)

Chapter 11
11-10 Respironics V200 Ventilator Operator’s Manual REF 1057983 A
Diagnostics
Self Test
Introduction
The Respironics V200 ventilator has an extensive system of checks designed
into the system to ensure that it operates safely and detects fault conditions
that can compromise the performance of the system as a ventilator. These
checks include hardware that checks the integrity of the software and software
that checks the hardware to ensure that it is operating within normal ranges.
These checks are described below.
Self-Test Hardware
The self-test hardware involves hardware components that check the integrity
of the software. The hardware components that perform these checks are the
watchdog timer and the bus activity monitor.
• Watchdog Timer: The watchdog timer is a timer that the software must
reset. If the timer times out, it causes a reset that restarts the
ventilator as if the power switch had been turned on. Normally the
software resets the watchdog timer and it never times out.
• Bus Activity Monitor: The bus activity monitor is a timer similar to the
watchdog timer. The bus activity monitor timer is a timer that only
times out if there has been no activity on the microprocessor bus. If
there is no activity on the bus, it would indicate there is a malfunction
of some kind and the microprocessor is restarted in the same way that
the watchdog timer does.
Power On Self Test (POST)
POST is the test that the ventilator does when the machine power is turned on
or if there has been a potential fault detected by the watchdog timer or the bus
activity monitor. POST has the constraint that it must be able to run safely
when the ventilator has a patient attached. POST checks the integrity of
critical system electronics such as the self test hardware and microprocessor
electronics. POST also tests other critical ventilator components that can be
tested.
A primary objective of POST is to ensure that the watchdog timer and the bus
activity monitor hardware are working and will catch software malfunctions.
These are critical components of the safety system and therefore POST tests
these components every time it runs.
POST also checks all critical digital hardware, including the processor,
program memory, data memory, and functions of various measurement
systems.
POST also checks pneumatic components that can be safely tested with the
safety valve open.
If all of these tests pass, the Respironics V200 ventilator will operate as a
ventilator.