2. DEFINITION
• The term capnography refers to the non
invasive measurement of the partial
pressure of carbon dioxide (CO2) in
exhaled breath expressed as the
CO2 concentration over time.
• The relationship of CO2 concentration
to time is graphically represented by the
CO2 waveform, or capnogram
3. • Capnography is the monitoring of
the concentration or partial
pressure of carbon dioxide (CO2) in
the respiratory gases.
• It is mainly used as a monitoring
tool for use
during anesthesia and intensive
care.
4. • It is usually presented as a graph of
expiratory CO2 (measured in
millimeters of mercury, "mmHg")
plotted against time, or, less
commonly, but more usefully,
expired volume.
• When the measurement is taken at
the end of a breath (exhaling), it is
called "end tidal" CO2 (ETCO2).
5. • During anesthesia, there is interplay
between two components: the patient
and the anesthesia administration
device (which is usually a breathing
circuit and a ventilator)
• The critical connection between the two
components is either an endotracheal
tube or a mask, and CO
2 is typically monitored at this junction.
6. • Capnography directly reflects the
elimination of CO2 by the lungs to
the anesthesia device.
• Indirectly, it reflects the production
of CO2 by tissues and the circulatory
transport of CO2 to the lungs.
12. DIAGNOSTIC USAGE
• Capnography provides information
about CO2 production, pulmonary
perfusion, alveolar ventilation, respira
tory patterns, and elimination of CO
2 from the anesthesia breathing
circuit and ventilator.
13. • The shape of the curve is affected by
some forms of lung disease; in
general there are obstructive
conditions such
as bronchitis, emphysema and asth
ma, in which the mixing of gases
within the lung is affected.
14. • Conditions such as pulmonary
embolism and congenital heart
disease, which affect perfusion of
the lung, do not, in themselves,
affect the shape of the curve, but
greatly affect the relationship
between expired CO2 and arterial
blood CO2
15. • Capnography can also be used to
measure carbon dioxide production, a
measure of metabolism.
Increased CO2 production is seen
during fever and shivering.
• Reduced production is seen during
anesthesia and hypothermia.
16.
17. ADVANTAGES
• This technique allows insight into
the alveolar ventilation, perfusion
and metabolism of breathing
• The appropriate tracing/mark on a
pulse oximeter guarantees that the
recorded oxygen saturation
provided is valid.
18. • Secondly, the evaluation of the
provided waveform gives key
information about latent,
underlying physiologic conditions
and the ongoing processes of
diseases.
19.
20. • Capnometry is a non-invasive
monitoring technique. It allows
quick and reliable insight into
aspects like: ventilation, circulation,
and metabolism.
• In diagnosis, monitoring, and
prediction of outcome capnometry
is an important tool, especially in
the pre-hospital setting
21. • Conditions such as pulmonary
embolisms (PE's) and congenital
heart disease, affecting perfusion of
the lung do not affect the shape of
the curve, but have an affect on the
relationship between
expired CO2 and arterial blood CO2.
22. • Capnography can also be used to
measure carbon dioxide production.
Increased CO2 production is seen
during fever and shivering. Reduced
production is seen during
anesthesia and hypothermia.
23. WORKING MECHANISM
• Capnographs usually work on the
principle that CO2 absorbs infrared
radiation. A beam of infrared light is
passed across the gas sample to fall on a
sensor.
• The presence of CO2 in the gas leads to a
reduction in the amount of light falling
on the sensor, which changes the
voltage in a circuit.
24. • The analysis is rapid and accurate,
but the presence of nitrous oxide in
the gas mix changes the infrared
absorption via the phenomenon of
collision broadening. This must be
corrected for measuring the CO2 in
human breath by measuring its
infrared absorptive power.
25. CAPNOGRAM MODEL
• The capnogram waveform provides
information about various respiratory
and cardiac parameters.
• The capnogram double-
exponential model attempts to
quantitatively explain the relationship
between respiratory parameters and
the exhalatory segment of a capnogram
waveform
27. • This model explains the rounded
"shark-fin" shape of the capnogram
observed in patients
with obstructive lung disease.
28. EMERGENCY MEDICAL SERVICES
Capnography is increasingly being
used by EMS personnel to aid in
their assessment and treatment of
patients in the pre hospital
environment.
29. • These uses include verifying and
monitoring the position of
an endotracheal tube or a blind
insertion airway device.
• A properly positioned tube in
the trachea guards the patient's airway
and enables the paramedic to breathe
for the patient. A misplaced tube in
the esophagus will lead to the patient's
death if it goes undetected.
30. • Capnography provides a rapid and
reliable method to detect life-
threatening conditions (malposition
of tracheal tubes, unsuspected
ventilatory failure, circulatory
failure and defective breathing
circuits) and to circumvent
potentially irreversible patient
injury.
31. • During procedures done under
sedation, capnography provides
more useful information, e.g. on the
frequency and regularity of
ventilation, than pulse oximetry.
32. • When expired CO2 is related to
expired volume rather than time,
the area beneath the curve
represents the volume of CO2 in the
breath, and thus over the course of
a minute, this method can yield
the CO2 per minute elimination, an
important measure of metabolism.
33. • Sudden changes in CO2 elimination
during lung or heart surgery usually
imply important changes in cardio
respiratory function.
34. • Changes in the shape of the
capnogram are diagnostic of disease
conditions, while changes in end-
tidal CO2 (EtCO2), the maximum
CO2 concentration at the end of
each tidal breath, can be used to
assess disease severity and
response to treatment.
35. • Capnography is also the most
reliable indicator that an
endotracheal tube is placed in
the trachea after intubation.
36. • Capnography provides
instantaneous information about
ventilation (how effectively CO2 is
being eliminated by the pulmonary
system), perfusion (how effectively
CO2 is being transported through
the vascular system), and
metabolism (how effectively CO2 is
being produced by cellular
metabolism).
37. PRINCIPLES OF OPERATION
Carbon dioxide (CO2) monitors
measure gas concentration, or
partial pressure, using one of
two configurations: mainstream
or sidestream.
38.
39. • Mainstream devices measure
respiratory gas (in this case CO2)
directly from the airway, with
the sensor located on the airway
adapter at the hub of the
endotracheal tube (ETT).
40.
41. • Sidestream devices measure
respiratory gas via nasal or
nasal-oral cannula by aspirating
a small sample from the exhaled
breath through the cannula
tubing to a sensor located inside
the monitor
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