Dr Meera Ekka Assistant Professor Department of Emergency Medicine AIIMS

1. ETCO2 IN NON-
INTUBATED PATIENT: A
MUST IN ED
Dr Meera Ekka
Assistant Professor Department of Emergency Medicine
AIIMS

2. Objectives
 Definitions
 Discuss Respiratory Cycle/Physiologic basis
 Why EtCo2 monitoring is Important
 Current Methods of Measuring ETCO2
 Discuss Non-intubated vs. intubated patient
uses
 Emerging uses in Non-Intubated patients
 Discuss different waveforms and treatments of
them.

3. So what is EtCO2?
 End-tidal CO2(EtCO2)- The maximum
concentration of carbon dioxide(CO2) in the
airway at the end of each tidal breath.
 Capnography- Provides a numeric
reading(amount) of the EtCO2 and a graphic
display(waveform) of CO2 throughout the
respiratory cycle
 Capnometry- Analysis only of the numeric
reading of CO2 ,no waveforms

4. Respiratory Cycle
 Breathing- Process of moving oxygen into the
body and CO2 out can be passive or non-
passive.
 Metabolism-Process by which an organism
obtains energy by reacting O2 with glucose to
obtain energy.
 Aerobic- glucose+O2 = water vapor, carbon
dioxide, energy (2380 kJ)
 Anaerobic- glucose= alcohol, carbon dioxide,
water vapor, energy (118 kJ)

5. Respiratory Cycle con’t
 Ventilation- Rate that gases enters and
leaves the lungs
 Minute ventilation- Total volume of gas entering
lungs per minute
 Alveolar Ventilation- Volume of gas that reaches
the alveoli
 Dead Space Ventilation- Volume of gas that does
not reach the respiratory portions ( 150 ml)

6. Oxygen -> lungs -> alveoli -> blood
muscles + organs
Oxygen
cells
Oxygen
Oxygen
+
Glucose
energy
CO2
blood
lungs
CO2
breath
CO2
Respiratory Cycle

7. METABOLISM PERFUSION VENTILATION
ALL THREE ARE IMPORTANT!
Respiratory Cycle

8. How is ETCO2 Measured?
 Semi-quantitative capnometry
 Quantitative capnometry
 Wave-form capnography

9. Semi-Quantitative Capnometry
 Relies on pH change
 Paper changes color
 Purple to Brown to Yellow

10. Quantitative Capnometry
 Absorption of infra-
red
light
 Gas source
 Side Stream
 In-Line/Main stream
Factors in choosing
device:
 Warm up time
 Cost
 Portability

11. Waveform Capnometry
 Adds continuous
waveform display to
the ETCO2 value.
 Additional
information in
waveform shape
can provide clues
about causes of
poor oxygenation.

12. EtCO2 Values
 Normal: 35 – 45 mmHg
 Hypoventilation > 45 mmHg
 Hyperventilation < 35 mmHg
PaCO2:
Normal Value:38-45mmHg
Excellent correlation between EtCO2 and
PaCO2

13.  Relationship between CO2 and RR
 ↑RR = ↓CO2 Hyperventilation
 ↓ RR = ↑ CO2 Hypoventilation
Physiology

14. Why ETCO2 I Have my Pulse
Ox?
Oxygen Saturation
Reflects
Oxygenation
SpO2 changes lag
when patient is
hypoventilating or
apneic
Should be used with
Capnography
Carbon Dioxide
Reflects Ventilation
Hypoventilation/Apn
ea detected
immediately
Should be used with
pulse Oximetry
Pulse Oximetry Capnography

15. What does it really do for me?
Bronchospasms:
Asthma, COPD,
Anaphylaxis
Hypoventilation:
Drugs, Stroke, CHF,
Post-ictal
Shock& Circulatory
compromise
Hyperventilation
Syndrome:
Biofeedback
Verification of ETT
placement
ETT surveillance
during transport
Control ventilations
during increased ICP
CPR: compression
efficacy, early signs of
ROSC, survival
predictor
Non-Intubated Applications Intubated Applications

16. Emerging use in Non-Intubated
patients
 Rapid assessment
of critically ill or
seizing patients
 Response to
treatment in
respiratory distress
 Adequacy of
ventilation seizing
or unconscious
patient
 Diabetic

17. NORMAL CAPNOGRAM

18. NORMAL CAPNOGRAM
 Phase I is the beginning of exhalation
 Phase I represents most of the anatomical
dead space
 Phase II is where the alveolar gas begins to
mix with the dead space gas and the CO2
begins to rapidly rise

19. NORMAL CAPNOGRAM
 Phase III corresponds to the elimination of
CO2 from the alveoli
 ET CO2 is measured at the maximal point of
Phase III.
 Phase IV is the inspirational phase

20. ABNORMALITIES
 Increased Phase III
slope
 Obstructive lung
disease
 Phase III dip
 Spontaneous resp
 Horizontal Phase III
with large ET-art CO2
change
 Pulmonary embolism
  cardiac output
 Hypovolemia
 Sudden  in ETCO2
to 0
 Dislodged tube
 Vent malfunction
 ET obstruction
 Sudden  in ETCO2
 Partial obstruction
 Air leak

21. ABNORMALITIES
 Gradual 
 Hyperventilation
 Decreasing temp
 Gradual  in
volume
 Sudden increase in
ETCO2
 Sodium bicarb
administration
 Release of limb
tourniquet
 Gradual increase
 Fever
 Hypoventilation
 Increased baseline
 Rebreathing
 Exhausted CO2
absorber

22. Normal Wave Form
 Square box
waveform
 ETCO2 35-45 mm
Hg
 Management:
Monitor Patient

23. Dislodged ETT
 Loss of waveform
 Loss of ETCO2
reading
 Management:
Replace ETT

24. Esophageal Intubation
 Absence of waveform
 Absence of ETCO2
 Management: Re-Intubate

25. CPR
 Square box waveform
 ETCO2 10-15 mm Hg (possibly higher) with
adequate CPR
 Management: Change Rescuers if ETCO2
falls below 10 mm Hg

26. Obstructive Airway
 Shark fin waveform
 With or without prolonged expiratory phase
 Can be seen before actual attack
 Indicative of Bronchospasm( asthma, COPD,
allergic reaction)

27. ROSC (Return of Spontaneous
Circulation)
 During CPR sudden increase of ETCO2 above
10-15 mm Hg
 Management: Check for pulse

28. Rising Baseline
 Patient is re-breathing CO2
 Management: Check equipment for adequate
oxygen flow
 If patient is intubated allow more time to
exhale

29. Hypoventilation
 Prolonged waveform
 ETCO2 >45 mm Hg
 Management: Assist ventilations or intubate as
needed

30. Hyperventilation
 Shortened waveform
 ETCO2 < 35 mm Hg
 Management: If conscious gives biofeedback.
If ventilating slow ventilations

31. Patient breathing around ETT
 Angled, sloping down stroke on the waveform
 In adults may mean ruptured cuff or tube too
small
 In pediatrics tube too small
 Management: Assess patient, Oxygenate,
ventilate and possible re-intubation

32. Take Home message
 EtCO2 is safe, non invasive, inexpensive, and
rapidly performed at bedside
 ETCO2 is a great tool to help monitor the
patients breath to breath status in emergency
settings.
 Can help recognize airway obstructions before
the patient has signs of attacks
 Helps you control the ETCO2 of head injuries
 Can help to identify ROSC in cardiac arrest
SO A MUST IN ED

33. Thank You forListening

34. LIMITATIONS
 Critically ill patients often have rapidly
changing dead space and V/Q mismatch
 Higher rates and smaller TV can increase the
amount of dead space ventilation
 High mean airway pressures and PEEP
restrict alveolar perfusion, leading to falsely
decreased readings
 Low cardiac output will decrease the reading

35. PaCO2-PetCO2 gradient
 Usually <6mm Hg
 PetCO2 is usually less
 Difference depends on the number of under
perfused alveoli
 Tend to mirror each other if the slope of Phase III
is horizontal or has a minimal slope
 Decreased cardiac output will increase the
gradient
 The gradient can be negative when healthy lungs
are ventilated with high TV and low rate
 Decreased FRC also gives a negative gradient by
increasing the number of slow alveoli

36. Interpretation of ETCO2
 Excellent correlation
between ETCO2 and
cardiac output when
cardiac output is low.
 When cardiac output is
near normal, then
ETCO2 correlates with
minute volume.
 Only need to ventilate as
often as a “load” of CO2
molecules are delivered
to the lungs and
exchanged for 02
molecules

37. USES
 Metabolic
 Assess energy expenditure
 Cardiovascular
 Monitor trend in cardiac output
 Can use as an indirect Fick method, but actual
numbers are hard to quantify
 Measure of effectiveness in CPR
 Diagnosis of pulmonary embolism: measure
gradient

38. PULMONARY USES
 Effectiveness of therapy in bronchospasm
 Monitor PaCO2-PetCO2 gradient
 Worsening indicated by rising Phase III without
plateau
 Find optimal PEEP by following the gradient.
Should be lowest at optimal PEEP.
 Can predict successful extubation.
 Dead space ratio to tidal volume ratio of >0.6 predicts
failure. Normal is 0.33-0.45
 Limited usefulness in weaning the vent when
patient is unstable from cardiovascular or
pulmonary standpoint
 Confirm ET tube placement

39. Curare cleft
 Curare Cleft is when
a neuromuscular
blockade wears off
 The patient takes
small breaths that
causes the cleft
 Management:
Consider
neuromuscular
blockade re-
administration

40. CAPNOGRAM #1
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997

41. CAPNOGRAM #2
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997

42. CAPNOGRAM #3
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997

43. CAPNOGRAM #4
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997

44. CAPNOGRAM #5
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997

45. CAPNOGRAM #6
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997

46. CAPNOGRAM #7
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997

47. CAPNOGRAM #8
J Int Care Med, 12(1): 18-32, 1997J Int Care Med, 12(1): 18-32, 1997