2. Objectives
• The terms of Capnography
• Capnography vs Oximetery
• Types of Capnography
• The Normal CO2 Waveform
• Different uses of Capnography
3. What is Capnography?
• “
• Capnos” = Greek for smoke
– From the “fire of life” metabolism
– CO2 is the waste product of metabolism
“CO2 is the smoke from the flames of
metabolism.”
-Ray Fowler, M.D. Dallas, Street Doc’s Society
4. Terminology
• ETCO2 (PeCO2) = End-Tidal CO2
• ETCO2 = C on the image below
– End-tidal CO2 is measured at the end of
expiration.
– The highest level of expired CO2 is ETCO2
• Normal ETCO2
– 35 to 45 mmHg
5. How is ETCO2 Measured?
• Semi-quantitative capnometry
• Quantitative capnometry
• capnography
10. Oxygenation and Ventilation
Oxygenation (Pulse Ox)
– O2 for metabolism
– SpO2 measures
% of O2 in RBCs
– Reflects changes in
oxygenation within
5 minutes
Ventilation (Capnography)
– CO2 from metabolism
– EtCO2 measures exhaled
CO2 at point of exit
– Reflects changes in
ventilation within
10 seconds
11. Capnography vs Oximetery
• Capnography gives an immediate picture
of the patient’s condition.
• Pulse oximetry is delayed.
• If you hold your breath…
– Capnography will show immediate apnea.
– O2 Saturations will remain normal for a
prolonged period of time.
16. Volume capnography.
• The expired CO2
waveform plotted
against expiratory flow
rate
• allows calculation of
total CO2 production
and respiratory dead
space.
• not widely used in
clinical practice.
18. Infrared Absorption
• A beam of infrared light
energy is passed through
a gas sample containing
CO2
• CO2 absorb specific
wavelengths .
• Light emerging from
sample is analyzed.
• A ration of the CO2
affected wavelengths to
the non-affected
wavelengths is re[ported
as ETCO2
20. Mainstream vs. Sidestream
•Shining a light directly through
the gas flow of the ventilator
circuit against an absorber
•A side stream of gas can
also be removed from the
ventilator circuit to a
separate analyser
23. Normal ETCO2
*Alterations in nasopharyngeal anatomy,
and device obstruction may alter the
ETCO2 reading.
Zero baseline (A-B)
Rapid, sharp rise (B-C)
Alveolar plateau (C-D)
End tidal value (D)
Rapid, sharp downstroke (D-E)
31. Intubation
• There is no better indicator of proper ET-
Tube placement than waveform
capnography.
• The presence of a waveform indicates a
tube is correctly placed in the trachea
Good Tube Bad Tube
32.
33. Intubation
• ETCO2 = 0 mmHg
• DOPE Pneumonic
– D - Dislodgement - check the tube!
– O - Obstruction - suction
– P - Pneumothorax - check lung sounds
– E - Equipment - check the vent
34. Airway:
Leaking tube cuff
Possible causes:
Leaky or deflated endotracheal or
tracheostomy cuff
Artificial airway too small for the patient
37. Monitoring Ventilation
• Hypoventilation causes an increased
ETCO2 (hypocapnia)
• A steadily rising ETCO2 (as the patient begins to
hypoventilate) can help a paramedic anticipate
when a patient may soon require assisted
ventilations or intubation.
39. Rebreathing
Possible causes:
Faulty expiratory valve
Inadequate inspiratory flow
Breath stacking (wrong mode, undersedated)
Malfunction of CO2 absorber system
40. “Curare Cleft”
•Capnography is also essential in sedated, intubated
patients.
• A small notch in the wave form indicates the patient is
beginning to arouse from sedation, and will need
additional medication to prevent them from "bucking" the
tube.
Called “curare cleft”
41. What about non intubated?
• End-tidal CO2 monitoring on non-intubated
patients
• excellent way to assess the severity of
Asthma/COPD, and the effectiveness of
treatment.
• Bronchospasm will produce a
characteristic “Shark fin” wave form, as the
patient has to struggle to exhale
43. The Shark Fin
Possible causes:
Partially kinked or occluded artificial airway
Presence of foreign body in the airway
Obstruction in expiratory limb of vent circuit
Bronchospasm
52. Cardiac Arrest
• Little O2 delivery or consumption
• Little CO2 production or venous
return
…Little Need to Ventilate!
53. EtCO2 and Cardiac Arrest
• EtCO2 had 90% sensitivity in predicting
ROSC
• Maximal level of <10mmHg during the first
20 minutes after intubation was never
associated with ROSC
Source: Canitneau J. P. 1996. End-tidal carbon dioxide during cardiopulmonary resuscitation in
humans presenting mostly with asystole, Critical Care Medicine 24: 791-796
54. EtCO2 and Cardiac Arrest
4 5
0
A spike in ETCO2 indicates return of
spontaneous circulation (ROSC
55. Monitoring Circulation
• The O2 in the cells is metabolized, and
CO2 is present, but stagnant in the body.
• The return of circulation causes a washout
of this CO2; which shows up as a spike in
ETCO2 levels.
57. Monitoring Circulation
• Pulmonary Embolus
– Pulmonary embolus will cause an increase in
the dead space in the lungs decreasing the
alveoli available to offload carbon dioxide.
– The ETCO2 will go down.
58. R. Fowler, P. Pepe
September, 2007
What about other shock states?
“These data suggest that
respiratory rate alone cannot
be used to predict
measured capnography levels.”
59. SHOCK?
• End tidal CO2 monitoring can provide an
early warning sign of shock.
• A patient with a sudden drop in cardiac
output will show a drop in ETCO2
numbers that may be regardless of any
change in breathing.
• This has implications for trauma patients,
cardiac patients - any patient at risk for
shock.
60. Monitoring Metabolism
• DKA - Patients with DKA hyperventilate to
lessen their acidosis.
• The hyperventilation causes their PACO2
to go down.
– Kussmal’s respirations are rapid & deep.
4 5
0
61. Monitoring Metabolism
• Hyperthermia
– Metabolism is on overdrive in fever, which
may cause ETCO2 to rise.
– Observing this phenomena can be live-saving
in patients with malignant hyperthermia
62. Monitoring Metabolism
• Sepsis
– ETCO2: 31-34 = Increased survivability
– ETCO2: Less than 30 = Increased morbidity
End-Tidal Carbon Dioxide Levels Are
Associated with Mortality In Emergency
Department Patients with Suspected
Sepsis
63. PaCO2-PetCO2 gradient
Usually <6mm Hg
PetCO2 is usually less
Difference depends on the number of
under perfused alveoli
Decreased cardiac output will increase the
gradient
64. GAP PCO2 –ETCO2
• If ventilation or perfusion are unstable, a
Ventilation/Perfusion (V/Q) mismatch can
occur.
• This will alter the correlation between
PaC02 and PetCO2.
• This V/Q mismatch can be caused by
blood shunting.
69. Take home message
• ETCO2 is a great tool to help monitor the
patients breath to breath status.
• Can help recognize airway obstructions before
the patient has signs of attacks
• Can help to identify ROSC in cardiac arrest
70. References
•Capnography, Bhavani Shankar Kodali, MD
•Capnography in ‘Out of Hospital’ Settings, Venkatesh
Srinivasa, MD, Bhavani Shankar Kodali, MD
Capnography, Novametrix Systems, Inc.
•Clinical Physiology of Capnography, Oridion Emergency
Medical Services
•Evolutions/Revolutions: Respiratory Monitoring,
RN/MCPHU Home Study Program CE Center
•End-Tidal Carbon Dioxide, M-Series, Zoll Medical
Corporation
71. Thank you for staying awake!
سَّمُهَّلال َكَانَحْبَُُحِبَو، َكِدْم،ْنَأُدَهْشَأ
َتْنَأ َّالِإَلهِإال،،ْغَتْسَأَلِإ ُوبْتَأَو َكُرِفَكْْي
سَّمُهَّلال َكَانَحْبَُُحِبَو، َكِدْم،ْنَأُدَهْشَأ
َتْنَأ َّالِإَلهِإال،،ْغَتْسَأَلِإ ُوبْتَأَو َكُرِفَكْْي
