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.
TreyMed 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.