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Airway gases
Basics of airway gases measurement
Airway gases measurement description, CARESCAPE
respiratory modules and compact airway modules
With CARESCAPE respiratory modules and compact airway modules, you can measure
and monitor gases being delivered to the patient and exhaled by the patient through
the breathing circuit. The modules consist of an infrared sensor for measuring CO
2
and N
2
O,and paramagnetic O
2
sensor. The E-sCAiO, E-sCAiOV, E-CAiO, E-CAiOV and
E-CAiOVX modules also include anesthetic agents measurement.
The gas sampling system samples the measured air to the module, and removes water
and impurities from it. The pump of the gas sampling system draws gas at a fixed rate
through the sampling line into the gas measuring units. The gas enters the module
through the water trap, where it is divided into two flows, a main flow and a side flow.
The main flow goes into the analyzers. This flow is separated from the patient side by a
hydrophobic filter. The side flow creates a slight sub-atmospheric pressure within the
water trap, which causes fluid removed by the hydrophobic filter to collect in the bottle.
After the measurement, gas is exhausted through the sample gas out connector.
NOTE
The gas sampling system of the E-COVX and E-CAiOVX
modules differs from that of the other compact airway
modules and the CARESCAPE respiratory modules. A number
of flow restrictors have been changed to create a bigger
pressure difference with ambient pressure in the gas sensors.
The sample flow is, however, approximately the same (200
ml/min). A larger pressure difference makes the deformations
of the gas concentration curves less sensitive to high
variations of the airway pressure.
Airway gases measurement description, E-miniC
The E-miniC is designed for critical care environment to measure and monitor the
expired and inspired CO
2
concentration (EtCO
2
, FiCO
2
) as well as the respiration rate
(RR) up to 80 breaths per minute. E-miniC has a sample flow of 150 ml/min.
Respiration rate from the CO
2
parameter is counted from the frequency of end-tidal
(peak) CO
2
measurements per minute. A sufficient respiration is defined as a
difference of at least 1% (at least 7 mmHg) between the measured inspired fraction
and end-tidal CO
2
.
Total sample size volume during one respiratory cycle depends on the respiration rate.
The following table shows different sample size volumes with a 150 ml/min sample
flow and I:E ratio of 1:2.
Respiration rate 10 20 30 40
Duration of
inspiration 2.0 seconds 1.0 seconds 0.7 seconds 0.5 seconds
Duration of
expiration 4.0 seconds 2.0 seconds 1.3 seconds 1.0 seconds
Volume
sampled during
inspiration 5 ml 2.5 ml 1.67 ml 1.25 ml
2062971-001 CARESCAPE Modular Monitors 297