AVEA ventilator systems 133
L2786 Rev. M
Chapter 5: Volumetric Capnography
Introduction
The Volumetric Capnography, Vco
2
Option for AVEA adds new monitoring and advanced calculation features. The
option requires purchase of the sensor and a software activation. In addition to traditional ETCO
2
and capnography,
there are features that assist the clinician with patient evaluation.
Warnings
Periodically check the CO
2
sensor for excessive moisture or secretion build up.
Volumetric capnography measurements require accurate measurement of delivered volumes. For this reason, a proximal
flow sensor or circuit compliance compensation must be used. Furthermore, when circuit compliance compensation is
used, and if the circuit compliance changes, volumetric accuracy will be altered.
A system leak, such as that caused by un-cuffed endotracheal tubes may affect flow-related readings. These include
flow, pressure, dead space, CO
2
production, and other respiratory mechanics parameters.
Nitrous oxide, excessive levels of oxygen, helium, and halogenated hydrocarbons can influence the CO
2
measurements.
The AVEA compensates for oxygen and helium gas automatically.
Do not use CO
2
measurements as the sole basis for changing ventilation parameters without reference to clinical
condition and independent monitors such as blood gas. CO
2
measurements may be inaccurate in the presence of a
breathing circuit leak, secretions, or sensor malfunction.
Do not position the CO
2
sensor or cable in any manner that may cause entanglement, strangulation, or accidental self-
extubation. Use clips as appropriate to secure the sensor cable to the breathing circuit.
Do not use EtCO
2
as basis for changing ventilation parameters without reference to clinical condition and independent
monitors such as blood gas.
Cautions
The CAPNOSTAT
®
5 contains no user serviceable parts.
Do not use damaged sensors or cables.
Do not sterilize or immerse sensors, except as directed in this manual.
Do not apply excessive tension to any sensor cable.
It is recommended that the CO
2
sensor be removed from the circuit whenever an aerosolized medication is delivered.
This is due to the increased viscosity of the medications, which may contaminate the sensor windows, causing the
sensor to fail prematurely or to display incorrect data.
Theory of Operation
The CAPNOSTAT
®
5 measures CO
2
by using the infrared absorption technique, which has endured and evolved in the
clinical setting for over the past two decades and remains the most popular and versatile technique. The principle is
based on the fact that CO
2
molecules absorb infrared (IR) light energy of specific wavelengths with the amount of energy
absorbed being directly related to the CO
2
concentration. When an IR beam is passed through a gas sample containing
CO
2
, the electronic signal from the photo detector (which measures the remaining light energy) can be obtained. This
signal is then compared to the energy of the IR source and calibrated to accurately reflect CO
2
concentration in the
sample.
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