Welch Allyn Connex IWS, Directions For Use Manual

Page: 236 / 266

CO2 specifications (for additional information, refer to the directions for use that accompanies
each accessory)
Capnography is a non-invasive method for monitoring the level of carbon dioxide in exhaled breath (etCO2) to assess a
patient’s ventilatory status.
Capnostream uses Microstream non–dispersive infrared (NDIR) spectroscopy to continuously measure the amount of
CO2 during every breath, the amount of CO2 present at the end of exhalation (etCO2), the amount of CO2 present during
inhalation (FiCO2), and the Respiratory Rate. Infrared spectroscopy is used to measure the concentration of molecules
that absorb infrared light. Because the absorption is proportional to the concentration of the absorbing molecule, the
concentration can be determined by comparing its absorption to that of a known standard.
The Microstream etCO2 consumables deliver a sample of the inhaled and exhaled gases from the ventilator consumable
or directly from the patient (via an oral/nasal cannula) into the monitor for CO2 measurement. Moisture and patient
secretions are extracted from the sample, while maintaining the shape of the CO2 waveform. The 50 ml/min. sampling
flow rate reduces liquid and secretion accumulation, decreasing the risk of obstruction in the sample pathway in humid
ICU environments. Once inside the Microstream CO2 sensor, the gas sample goes through a micro-sample cell (15
microliters). This extremely small volume is quickly flushed, allowing for fast rise time and accurate CO2 readings, even
at high respiration rates. The Micro Beam IR source illuminates the micro-sample cell and the reference cell. This
proprietary IR light source generates only the specific wavelengths characteristic of the CO2 absorption spectrum.
Therefore, no compensations are required when different concentrations of N2O, O2, anesthetic agents and water vapor
are present in the inhaled and exhaled breath. The IR that passes through the micro-sample cell and the IR that passes
through the reference cell are measured by the IR detectors. The microprocessor in the monitor calculates the CO2
concentration by comparing the signals from both detectors.
Accuracy
1
0 to 38 mmHg: ±2 mmHg
39 to 150 mmHg: ±(5% of r 0.08% for every 1 mmHg
above 38 mmHg)
Flow rate 50 (42.5
≤
flow
≤
65) ml/min, flow measured by volume
Initialization time 40 seconds (typical, includes power-up and initialization
time)
System response time 7 seconds (typical, includes module response time and host
monitor system response time)
Compensation
Pressure
The CO2 module is equipped with a barometric pressure
transducer and compensation is triggered at startup or
during other events (significant changes in temperature,
ambient pressure, etc.).
BTPS (standard correction used by Microstream capnography
during all measurement procedures for body temperature,
pressure, and saturation).
Gases
The Microstream emitter radiates a focused beam of
infrared energy characterized by the narrow region (0.15 µm
wide) of the spectrum where CO2 molecules absorb infrared
radiation. Because MCS™ is highly accurate with all gas
samples, there is no need to create special algorithms within
the monitor to correct for high concentrations of oxygen or
anesthetic gases.
Cyclical pressure
≤
10 kPa (100 cmH
2
O); module operates within specification
with overpressure up to 100 cmH
2
O
Sampled gas return/disposal Sampled gases are not returned to the breathing circuit.
Exhaled gas is exhausted from the monitor's exhaust port.
230 Specifications Welch Allyn Connex
®
Devices