BD Alaris - Principle of Operation

Chapter 6—Alaris™ EtCO
2
Module Model 8300
306 BD Alaris
TM
System with Guardrails
TM
Suite MX User Manual
Principle of Operation
The EtCO
2
module uses Medtronic's patented Microstream nondispersive infrared (NDIR) spectroscopy to
continuously measure the amount of CO
2
during every breath, the amount of CO
2
present at the end of
exhalation (EtCO
2
) and during inhalation (FiCO
2
), and the respiratory rate. The EtCO
2
module is a side
stream capnograph.
The Microstream disposables deliver a s
ample of the inhaled and exhaled gases from the ventilator
disposable or directly from the patient (via an oral/nasal cannula) in
to the monitor for CO
2
measurement.
Moisture and patient secretions are extracted from the sample by the Microstream inline filter while
maintaining the shape of the CO
2
waveform.
The 50 mL/min sampling gas flowrate reduces liquid and secre
tion accumulation, decreasing the risk of
obstruction in the sample pathway in humid ICU environments. The small sample size eliminates the need
for water traps and prevents excess fluid accumulation.
The EtCO
2
module draws a gas sample through a microsample cell (15 microliters). This extremely small
volume is quickly flushed, allowing for a rise time of approximately 190 ms and accurate CO
2
readings,
even at high respiration rates.
The Microbeam IR source illuminates the microsample cell and the
reference
channel. This proprietary IR
light source generates only the specific wavelengths characteristic of the CO
2
absorption spectrum. The IR
light that passes through the microsample cell and the IR light that passes through the referen
ce channel
are measured by IR detectors.
The microcomputer in the EtCO
2
module calculates the CO
2
concentration by comparing the signals from
both channels.
No operator intervention is required for routine moisture or cond
ensate.
Hypoventilation with Shallow Breathing
• Medication effect
• Low tidal volume
No Breath Detected
•Apnea
• Very shallow breathing
• Overmedication
• Displaced cannula
Waveform Possible Causes