End tidal co2 and transcutaneous carbon dioxide monitors

1. 1.End tidal carbon dioxide
analysis
2.Transcutaneous and carbon dioxide
monitors

2. Introduction
• Capnometry refers to the measurement and
quantification of inhaled or exhaled CO2
concentrations at the airway opening.
• Capnography, however, refers not only to the
method of CO2 measurement, but also to its
graphic display as a function of time or
volume.

3. PHYSIOLOGY OF CAPNOMETRY

4. Oxygenation and Ventilation
Oxygenation
(oximetry)
Cellular
Metabolism
Ventilation
(capnography)
CO2
O2

5. Oxygenation and Ventilation
• Oxygenation
– Oxygen for metabolism
– SpO2 measures
% of O2 in RBC
– Reflects change in
oxygenation within
5 minutes
• Ventilation
– Carbon dioxide
from metabolism
– EtCO2 measures
exhaled CO2 at
point of exit
– Reflects change in
ventilation within
10 seconds

6. CO2 transport

7. End-tidal CO2 (EtCO2)
• Reflects changes in
– Ventilation - movement of air in and
out of the lungs
– Diffusion - exchange of gases between the
air-filled alveoli and the pulmonary
circulation
– Perfusion - circulation of blood

8. End-tidal CO2 (EtCO2)
r r Oxygen
O
2
CO2
O
2
VeinA te y
Ventilation
Perfusion
Pulmonary Blood Flow
Right
Ventricle
Left
Atrium

9. End-tidal CO2 (EtCO2)
• Monitors changes in
– Ventilation - asthma, COPD, airway
edema, foreign body, stroke
– Diffusion - pulmonary edema,
alveolar damage, CO poisoning, smoke
inhalation
– Perfusion - shock, pulmonary embolus,
cardiac arrest,
severe dysrhythmias

11. PRINCIPLES OF CAPNOGRAPHY

12. BEER-LAMBERT LAW

13. Types of sensors
Solid state CO2 sensors
Chopper wheel CO2 sensor

14. Sidestream vs Mainstream
Capnometry
Sidestream/ Diverging
• CO2 sensor located away from the
airway gases to be measured.
• Incorporate a pump or
compressor.
• Tubing length- 6 ft
• Gas withdrawal rate 30-
500ml/min
• Lost gas volume needs to be
considered in closed circuit
anesthesia.
• Gases must pass through various
water traps and filters.
• Transport delay time
• Associated RISE TIME
Mainstream/ Non- diverting
• Sample cell placed directly in the
patients breathing circuit.
• Inspiratory and expiratory gases
pass directly through the IR path
• Increase in dead space and is
heavy
• Sample cell heated to 40 degrees
to minimize condensation.
• Increased risk of facial burns.
• Requires daily calibration.
• No delay time
• RISE TIME is faster

15. Types of capnometers

16. CAPNOGRAPHY WAVEFORMS
Interpretation of TIME

17. Capnographic Waveform
• Normal waveform of one respiratory cycle
• Similar to ECG
– Height shows amount of CO2
– Length depicts time

18. Capnographic Waveform
• Waveforms on screen and printout
may differ in duration
– On-screen capnography waveform is condensed to
provide adequate information the in 4-second
view.

19. Capnographic Waveform
• Capnograph detects only CO2
from ventilation
• No CO2 present during inspiration
– Baseline is normally zero
A B
C D
E
Baseline

20. Capnogram Phase I
Dead Space Ventilation
• Beginning of exhalation
• No CO2 present
• Air from trachea,
posterior pharynx,
mouth and nose
– No gas exchange
occurs there
– Called “dead space”

21. Deadspace

22. Capnogram Phase I
Baseline
Beginning of exhalation
A
B
I Baseline

23. Capnogram Phase II
Ascending Phase
• CO2 from the alveoli begins to
reach the upper airway and
mix with the dead space air
– Causes a rapid rise in the
amount of CO2
• CO2 now present and detected
in exhaled air
Alveoli

24. Capnogram Phase II
Ascending Phase
CO2 present and increasing in exhaled air
II
A B
C
Ascending Phase
Early Exhalation

25. Capnogram Phase III
Alveolar Plateau
• CO2 rich alveolar gas
now constitutes the
majority of the
exhaled air
• Uniform concentration
of CO2 from alveoli to
nose/mouth

26. Capnogram Phase III
Alveolar Plateau
CO2 exhalation wave plateaus
A B
C D
III
Alveolar Plateau

27. Capnogram Phase III
End-Tidal
• End of exhalation contains the highest
concentration of CO2
– The “end-tidal CO2”
– The number seen on your monitor
• Normal EtCO2 is 35-45mmHg

28. Capnogram Phase III
End-Tidal
End of the the wave of exhalation
A B
C D End-tidal

29. Capnogram Phase IV
Descending Phase
• Inhalation begins
• Oxygen fills airway
• CO2 level quickly
drops to zero
Alveoli

30. Capnogram Phase IV
Descending Phase
Inspiratory downstroke returns to baseline
A B
C D
E
IV
Descending Phase
Inhalation

31. Capnography Waveform
Normal range is 35-45mm Hg (5% vol)
Normal Waveform
45
0

32. a-A Gradient
r r Alveolus
PaCO2
VeinA te y
Ventilation
Perfusion
arterial to Alveolar Difference for CO2
Right
Ventricle
Left
Atrium
EtCO2

35. End-tidal CO2 (EtCO2)
• Normal a-A gradient
– 2-5mmHg difference between the EtCO2
and PaCO2 in a patient with healthy lungs

36. Factors Affecting ETCO2 Levels

37. 45
0
Hyperventilation
RR : EtCO2
45
0
Normal
Hyperventilation

38. Waveform:
Regular Shape, Plateau Below Normal
• Indicates CO2 deficiency
 Hyperventilation
 Decreased pulmonary perfusion
 Hypothermia
 Decreased metabolism
• Interventions
 Adjust ventilation rate
 Evaluate for adequate sedation
 Evaluate anxiety
 Conserve body heat

39. Hypoventilation
45
0
45
0
RR : EtCO2
Normal
Hypoventilation

40. Waveform:
Regular Shape, Plateau Above Normal
• Indicates increase in ETCO2
 Hypoventilation
 Respiratory depressant drugs
 Increased metabolism
• Interventions
 Adjust ventilation rate
 Decrease respiratory depressant drug dosages
 Maintain normal body temperature

41. Bronchospasm Waveform Pattern
• Bronchospasm hampers ventilation
– Alveoli unevenly filled on inspiration
– Empty asynchronously during expiration
– Asynchronous air flow on exhalation dilutes exhaled
CO2
• Alters the ascending phase and plateau
– Slower rise in CO2 concentration
– Characteristic pattern for bronchospasm
– “Shark Fin” shape to waveform

42. Capnography Waveform Patterns
45
0
Normal
Bronchospasm
45
0

43. Capnography Waveform Patterns
45
0
Hypoventilation
Normal
45
0
45
0
Bronchospasm
Hyperventilation
45
0

44. Airway obstruction Cardiogenic oscillations
Curare Cleft Esophageal Intubation

45. Rebreathing of CO2 Faulty inspiratory valve
Patient with single lung transplant Faulty inspiratory valve

46. Ruptured/ Leaking ET tube cuff Leak in side stream sample line
Expiratory valve stuck open
Electrical Noise

50. VOLUME CAPNOGRAM

51. Volume Capnogram

52. Acute Bronchospasm
Changes in pulmonary perfusion

53. Advantages of volume capnogram
• Allows for estimation of the relative contributions of anatomic
and alveolar components of Vd.
• More sensitive than the time capnogram in detecting subtle
changes in dead space that are caused by alterations in PEEP,
pulmonary blood flow, or ventilation heterogeneity.
• Allows for determination of the total mass of CO2 exhaled
during a breath and provides for estimation of V˙ CO2.

54. USES OF CAPNOGRAPHY

55. Detect ET Tube
Displacement
Confirm ET Tube
Placement

56. Capnography in
Cardiopulmonary Resuscitation
• Assess chest compressions
• Early detection of ROSC
• Objective data for decision to cease resuscitation
• Use feedback from EtCO2 to depth/rate/force of chest
compressions during CPR.

57. In Laparoscopic Surgeries
1.Non invasive monitor of PaCO2 and can be used to adjust ventilation.
2.Detection of accidental intravascular CO2 insufflation.
3.Helps to detect complications of CO2 insufflation like pneumothorax.

58. Optimize Ventilation
• Use capnography to titrate EtCO2 levels
in patients sensitive to fluctuations
• Patients with suspected increased intracranial
pressure (ICP)
– Head trauma
– Stroke
– Brain tumors
– Brain infections

59. Optimize Ventilation
• High CO2 levels induce
cerebral vasodilatation
– Positive: Increases CBF to
counter cerebral hypoxia
– Negative: Increased CBF,
increases ICP and may increase
brain edema
• Hypoventilation retains CO2
which increases levels
CO2

60. Optimize Ventilation
• Low CO2 levels lead to cerebral
vasoconstriction
– Positive: EtCO2 of 25-30mmHG causes a
mild cerebral vasoconstriction which
may decrease ICP
– Negative: Decreased ICP but
may cause or increase in
cerebral hypoxia
• Hyperventilation decreases
CO2 levels CO2

61. The Non-intubated Patient
Capnography Applications
• Identify and monitor bronchospasm
– Asthma
– COPD
• Assess and monitor
– Hypoventilation states
– Hyperventilation
– Low-perfusion states

62. Capnography in
Bronchospastic Conditions
• Air trapped due to irregularities
in airways
• Uneven emptying of alveolar
gas
– Dilutes exhaled CO2
– Slower rise in CO2 concentration
during exhalation
Alveoli

63. Capnography in
Bronchospastic Diseases
• Uneven emptying of alveolar gas
alters
emptying on exhalation
• Produces changes in ascending
phase (II)
with loss of the sharp upslope
• Alters alveolar plateau
(III) producing a “shark fin”
A B
C D
E
II
III

64. Capnography in Bronchospastic Conditions
AsthmaCase
Initial
After therapy

65. Capnography in Bronchospastic Conditions
Pathology of COPD
• Progressive
• Partially reversible
• Airways obstructed
– Hyperplasia of mucous glands &
smooth muscle
– Excess mucous production
– Some hyper-responsiveness

66. Capnography in Bronchospastic Conditions
Capnography in COPD
• Arterial CO2 in COPD
– PaCO2 increases as disease progresses
– Requires frequent arterial punctures for ABGs
• Correlating capnograph to patient status
– Ascending phase and plateau are altered by
uneven emptying of gases

67. Capnography in
Hypoventilation States
• Altered mental status
– Sedation
– Alcohol intoxication
– Drug Ingestion
– Stroke
– CNS infections
– Head injury
• Abnormal breathing
• CO2 retention
– EtCO2 >50mmHg

68. Capnography Applications
on Non-intubated Patients
• New applications now being reported
– Pulmonary emboli
– CHF
– DKA
r r O xy g e n
O 2
V e inA te y

69. PULMONARY EMBOLUS

70. TRANSCUTANEOUS AND CARBON
DIOXIDE MONITORS

71. • Transcutaneous measurements of PO2 (Ptco2) and Pco2
(Ptcco2) are monitoring methods that aim to provide
noninvasive estimates of arterial O2 and CO2, or at least
trends associated with these variables.
• Transcutaneous monitoring can be applied when expired
gas sampling is limited.
• The measurements are based on the diffusion of O2 and
CO2 through the skin.
• Used successfully in neonates and infants

72. • Applied when expired gas sampling is limited
• Measurements are based on the diffusion of CO2
and O2 through the skin.
• Warming is used to facilitate gas diffusion.
• Such an increase in temperature promotes
increased O2 and CO2 partial pressure at skin
surface.
• Ptco2 is usually lower than PaO2, and Ptcco2 is
higher than Paco2.

73. • A transducer using a pH electrode to measure
the Pco2 (Stow-Severinghaus electrode) is
used.
• A change in pH is proportional to the
logarithm of the Pco2 change. For CO2
monitors
• A temperature correction factor is used to
estimate Paco2 from Ptcco2.

75. Uses of Ptcco2
1. Assess the efficacy of mechanical ventilation
in respiratory failure.
2. Laparoscopic surgery with prolonged
pneumoperitoneum.
3. Deep sedation for ambulatory hysteroscopy
in healthy patient.
4. Weaning from mechanical ventilation after
off pump CABG.

76. Uses of Ptco2
• Detect hyperoxia in neonates
• Adults:
1. Wound management
2. peripheral vascular disease
3. hyperbaric medicine.

77. Limitations
• Poor cutaneous blood flow
• Frequent calibration
• Slow response time
• Skin burns with prolonged application

78. References
• Understanding anesthesia equipment, 5th
edition Dorsch and Dorsch
• Miller’s Anesthesia 8th edition
• Care fusion capnography handbook
• www.capnography.org

79. THANK YOU
THE END