sudden drop in ETCO2

1. SUDDEN INTRA OPERATIVE LOSS OF ETCO2
DR.SHLOKA ANVI

2. HISTORY:
• Capnometry-First time during World war ll as a tool for monitoring internal
environment
• In medicine-1950.In Practice 1980’s
• Ramwell – proved it beyond doubt.
• 1978 – Holland the first country to adopt.
• 1999 – ISA ‘desirable standard’ in anaesthesia monitoring standards.

3. CAPNOGRAPHY:
• It provides information about CO2 production, pulmonary perfusion, alveolar
ventilation, respiratory patterns and elimination of CO2 from the anaesthesia
circuit and ventilator.
• Capnography is an indirect monitor, helps in differential diagnosis of hypoxia to
enable remedial measures to be taken before hypoxia results in an irreversible
brain damage.
• It has shown to be effective in the early detection of adverse respiratory events.
• Breath to breath measurement,Provides information within seconds

4. TYPES OF CAPNOGRAPHY:
VOLUME CAPNOGRAPHY TIME CAPNOGRAPHY

5. TIME CAPNOGRAPHY:
ADVANTAGES:
• Simple and convenient.
• Monitor non-intubated patients.
• Monitor dynamics of inspiration as
well as expiration.
DISADVANTAGES:
• Poor estimation of V/Q status of the
lung.
• Cant be used to estimate
components of physiological dead
space.

6. MAIN-STREAM CAPNOGRAPHY:
• CO2 sensor located between
endotracheal tube and breathing
circuit.

7. MAIN-STREAM CAPNOGRAPHY:
ADVANTAGES:
No sampling tube
No obstruction
No affect due to pressure drop
No affect due to changes in water vapor pressure
No pollution
No deformity of capnograms due to non dispersion of gases
No delay in recording
Suitable for neonates and children
DISADVANTAGES:
Contrary to the earlier versions, the newer sensors are
light weight minimizing traction on the endotracheal
tube.
Long electrical cord, but it is lightweight.
Facial burns have been reported with earlier versions.
This has been eliminated with newer sensors.
Sensor windows may clog with secretions. However,
they can be replaced easily as they are disposable.
Difficult to use in unusual patient positioning such as in
prone positions.
The newer versions use disposable sensor windows
thereby eliminating sterilization problem.

8. SIDE-STREAM CAPNOGRAPHY:
• Sensor is located in the main unit and
CO2 is aspirated via a sampling tube
connected to a T-piece adapter
located endotracheal tube and
breathing circuit.

9. SIDE-STREAM CAPNOGRAPHY:
ADVANTAGES:
Easy to connect.
No problems with sterilization.
Can be used in awake patients.
Easy to use when patient is in unusual positions
such as in prone position.
Can be used in collaboration with simultaneous
oxygen administration via a nasal prongs.
DISADVANTAGES:
Delay in recording due to movement of gases from
the ET to the unit.
Sampling tube obstruction.
Water vapor pressure changes affect
CO2concentrations.
Pressure drop along the sampling tube affects
CO2measurements.
Deformity of capnograms in children due to
dispersion of gases in sampling tubes.

11. COMPONENTS OF CAPNOGRAPHY:
• Normal waveform of one respiratory cycle similar to ECG.
- Height shows amount of Co2.
- Length depicts time.
• Capnography detects only Co2 from ventilation.
• No Co2 present during inspiration.
- Baseline is normally zero.
- Phase 1, Phase 11,Phase 111

18. INSPIRATORY SEGMENT:
• Phase 0: Inspiration.
• Beta angle: Angle between phase III
and descending limb of inspiratory
segment.

19. EXPIRATORY SEGMENT:
• Phase I: Anatomical dead space.
• Phase II: Mixture of anatomical and
alveolar dead space.
• Phase III: Alveolar plateau.
• Alfa angle: Angle between phase II
and phase III.

20. CAPNOGRAPHIC WAVE PATTERNS:
1. Normal waveform:
• Normal range is 35 – 45 mmHg.
II. HYPERVENTILATION:
III. HYPOVENTILATION:

22. OESOPHAGEAL INTUBATION:

23. BASE LINE ELEVATED IN:
• Inadequate fresh gas flow.
• Accidental administration of CO2.
• Rebreathing.
• Inspiratory / Expiratory valve malfunction.
• Exhausted CO2 absorber.
• The waveform reflects an elevation of
baseline, as well as the plateau, indicating
incomplete exhalation. The CO2 is not being
appropriately removed. This is often due to
insufficient expiratory time, inadequate
inspiratory flow, or faulty expiratory valve

24. SUDDEN INTRAOP LOSS OF ETCO2 CAUSES:
• A sudden drop in EtCO2, but with a square wave capnography trace still seen,
suggests a sudden drop in lung perfusion, either caused by an obstruction to
blood flow through the lungs (caused by thrombus, air or fat) or by a
reduction in cardiac output.

27. CAPNOGRAPHY IN CARDIAC ARREST:

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