Welch Allyn LC101 CO2 Module - User Manual - Manual (Page 8)

LC101 CO
2
Module OEM Implementation Manual
Page 8 Confidential Welch Allyn OEM Technologies
Terminology
Capnography is the noninvasive measurement and graphic display of airway CO
2
concentration
as a function of time. The resulting waveform is called a capnogram. The evaluation of the
capnogram is useful in the assessment of the adequacy of carbon dioxide exchange in the lungs,
integrity of the patient’s airway, cardiopulmonary function and ventilator function.
Capnogram Components
Monitoring of CO
2
concentration at the end of expiration (point D) is referred to as End-Tidal CO
2
(ETCO
2
) monitoring.
Mainstream vs. Sidestream
The patient’s expired gas may be sampled either directly off the patient airway external to the
LC101 Module or aspirated from the patient through a cannula into the Module. The method used
is dependent on the patient’s airway status.
Mainstream capnography is typically used on intubated or tracheostomy patients and requires
the use of an external mainstream sensor. Intubation is the process of inserting a tube into the
patient’s trachea to deliver gases to the lungs.
Sidestream capnography is used on patients who are intubated or non-intubated. The patient’s
expired gas is aspirated from the airway and transported to the LC101 Module through a sample
line. The sidestream sample chamber and sensor are embedded within the LC101 Module.
Signal acquisition and measurement calculation are performed by the LC101 Module.
Measuring Principle
CO
2
measurement is based on the Infra-Red (IR) absorption characteristics of CO
2
molecules.
The CO
2
sensor uses non-dispersive IR spectroscopy to measure the number of CO
2
molecules
present in the sample gas. CO
2
gas has a unique absorption band which is related to a CO
2
molecule’s composition and mass. CO
2
gas concentration is measured by detecting absorption in
this band. Due to the nature of the measurement technique employed, user calibration is
necessary with this system.
76
CO
2
(mmHg)
Time
40
0
A B
C D
E