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 The
OEM Compact CO2 Waveform Analyzer (CO2WFA) is a complete data collection and
analysis system for monitoring respiratory carbon dioxide concentration. The
CO2WFA module includes a miniature CO2 sensor, barometric pressure
transducer, sampling flow control and a miniature low-power vacuum pump. A
microprocessor collects the sensor data and calculates various real-time
parameters: instantaneous CO2 concentration, respiration rate, end-tidal
CO2, inspired CO2, inspiration and expiration times.
The module is highly configurable to meet
most OEM implementation requirements. System specifications such as
baud rate, parity, waveform data rate, sampling flow rate and floating point
data format can be programmed at the factory for custom configurations.
Special low cost configurations without flow rate control or automatic offset
calibration are available per special request.
Interfacing to the CO2WFA module is very
simple. The module requires a +5V supply at 400mA maximum current (200mA
typical). The host sends commands and receives waveform, breath parameters
and command responses via 3.3V asynchronous serial data lines.
The pump provided with the CO2WFA module
is capable of sampling patient gas at 50-250 cc/min. A flow regulation
system controls the gas flow rate, and attempts to clear the sample line if
it gets occluded. The CO2WFA notifies the host system of the occlusion via
the status packet of the communication protocol. The exhaust port of the
pump is typically connected to an exhaust port on the exterior of the host
device to allow connection to a hospital scavenging system. Another gas
reservoir on the exhaust port of the pump may help to reduce the audible
noise level of the system. Note: on low-cost versions of the module, the
Sample Gas Flow Control system will be removed, and the pump is simply
powered by a fixed voltage. Sample line occlusions are detected by the
amount of vacuum being drawn or the excessive current required by the pump.
The CO2WFA module was designed to
automatically perform calibrations in order to correct for changes in
temperature, altitude and electronic component drift. A solenoid valve on
the module occasionally switches from the patient line to ambient air
for a few seconds in order to collect a reference point used in the CO2
calculation. If the air surrounding the CO2WFA module may have elevated
concentrations of CO2 present (such as in an enclosed compartment or room
with poor ventilation), we recommend cleaning the CO2 from the ambient air
with a SODASORB™ filter connected to the offset port of the solenoid valve.
CPT can provide this as an option to the CO2WFA system. Note: on low-cost
versions of the module, the offset calibration valve is removed, and the
module will only perform offset calibration when commanded by the host
system (room air with no CO2 must be provided at the sample line input
during this calibration cycle).
The CO2WFA CO2 Module is available for evaluation and
product development by purchasing our CO2
Evaluation Kit. |
