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1. Capnography
Prepared By:
The Anesthesia Team
Al Shifa Medical Complex
Palestine
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2. Outlines
• History
• Standards for basic anesthetic monitoring
• Introduction
• Capnography principle
• Types of capnograph
• Normal capnogram
• Abnormal ETCO2 values
• Abnormal waveform.
• Capnography Vs Pulse Oximetry.
• Capnography and CPR.
• tips

3. History
 In 1943, luft developed the principle of capnography based on the fact
that CO2 absorbs infrared light.
 In the 1970s capnography was first studied clinically by smallhout and
kalenda in humans and has since been researched extensively.
 By 1985, capnography was considered the standard of care for basic
anesthesia monitoring by the american society of anesthesiologists.
 In the mid-1990s, co2 monitors (capnographs) became small and
inexpensive enough to be used in veterinary medicine
Capnography minimizes the need for repetitive arterial blood gas
sampling, thus providing an excellent noninvasive monitoring and diagnostic
tool.

4. Standards for basic anesthetic monitoring
 ASA standard II :
“During all anesthetics, the patient’s oxygenation, ventilation, circulation and
temperature shall be continually evaluated.”
“Every patient receiving general anesthesia shall have the adequacy of
ventilation continually evaluated.
 Qualitative clinical signs such as chest excursion, observation of the reservoir
breathing bag and auscultation of breath sounds are useful.
Continual monitoring for the presence of expired carbon dioxide shall be
performed unless invalidated by the nature of the patient, procedure or
equipment.
 Quantitative monitoring of the volume of expired gas is strongly encouraged.”*
• Developed by: committee on standards and practice parameters (CSPP)
last affirmed: december 13, 2020 (last amended october 20, 2010) (original approval: october 21, 1986)

5. Introduction
Definitions
 the term capnography refers to the noninvasive 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
Capnography constitutes an important non-invasive technique that can continuously
monitors:
1. C02 production,
2. Pulmonary perfusion
3. alveolar ventilation.
4. respiratory patterns.
5. Cardiac output
6. Cellular metabolism

6. Introduction
 The measurement of c02 in the expired air:
1- Directly indicates:
changes in the elimination of c02 from the lungs
(ventilation)
2- Indirectly it indicates:
 changes in the production of c02 at the tissue
level.(metabolism)
 the delivery of c02 to the lungs by the circulatory
system.(C.O.)

7. Capnography principle
 Principle of action (infra red absorption)
A beam of infrared light energy is passed
through a gas sample containing CO2.
 CO2 molecules absorb specific wavelengths of IR
light.
Light emerging from sample is analyzed.
 A ratio of the CO2 affected wavelengths to the
non-affected wavelengths is reported as ETCO2.

8. Types of capnograph
1- conventional technology
A- mainstream capnographs:
Sensor is located on a special airway adapter.
 CO2 is measured directly in the patient's breathing circuit.
 Disadvantages :
heavy weight of the sensor on the airway.
External sensors that are vulnerable to damage.
 inability to monitor non-intubated patients easily.
• B- sidestream capnographs:
• A sample of exhaled breath is aspirated from the breathing circuit to a sensor
residing inside the monitor.
Disadvantages:
• Liquid and secretion handling
• Large breath sample rate; precludes use of low-flow applications (neonates).

9. Types of capnograph
2- Microstream:
molecular correlation spectroscopy (MCS™) technology
 It could be sidestream or main stream
 intubated and non-intubated.
 No dilution with supplementary O2.
 monitor patients with high respiration rates
(above 100 bpm) and low tidal volumes.
 Capnometry vs capnography

10. Normal capnogram
1-Phase I (expiratory baseline)
 Is the beginning of exhalation
 corresponds to exhalation of CO2 free dead space
gas from the larger conducting airways.
 The CO2 value during this phase should be zero.
2- Phase ii (expiratory upstroke)
 Involves exhalation of mixed alveolar and
decreasing dead space gas,
 which rapidly increases the CO2 concentration.

11. Normal capnogram
3- Phase III (expiratory plateau)
 Occurs when all the dead space gas has been exhaled.
 resulting in exhalation of completely alveolar air.
 The highest point of phase III corresponds with the actual ETCO2 value.
 The plateau has a slight positive slope because of the continuous diffusion of CO2
from the capillaries into the alveolar space.
4- Phase 0 (inspiratory downstroke)
 Because of inhalation of co2-free gas,
 the CO2 concentration rapidly declines­to zero.
 The alpha angle (100°-110°)
• an indirect indication of the VA/Q status of the lungs.
 The beta angle (90°)
• The beta angle is used to assess the degree of rebreathing.

12. Abnormal ETCO2 values
 Common causes of decrease and increased ETCO2 values

13. Abnormal waveform
 The normal baseline (phase I) is zero. (inspiratory phase)
 An increase in the baseline represents rebreathing of expired CO2.
 A rise in the baseline is seen in:
1-exhausted soda lime absorber, 2- faulty one-way valves,
3- inadequate fresh gas flow rates are used.
 If both the baseline and ETCO2 values rise precipitously, the sensor may be contaminated
with secretions.

14. Abnormal waveform
In a normal capnogram, the expiratory upstroke (phase II) is steep.
 If the upstroke slope is lessened, CO2 delivery to the sampling site may
be delayed.
 This delay could be physiologic or mechanical.
1- Mechanical factors include obstruction of the breathing circuit with:
 secretions , condensation, or kinking.
as well as a delay in the sampling rate with sidestream analyzers.
2- Physiologic factors of a slow upstroke include:
 uneven alveoli emptying typical of that found in asthma or bronchitis.

15. Abnormal waveform
Normally the expiratory plateau (phase III) should be nearly horizontal,
 The highest point of the plateau representing the actual ETCO2 value.

16. Abnormal waveform
The inspiratory downstroke (phase 0).
It is a nearly vertical drop to baseline.

17. Capnography Vs Pulse Oximetry
ETCO2 has been shown to be superior to pulse oximetry in early detection
of airway mishaps, both technical and pathophysiologic.
 It takes a longer time for oxygen saturation to drop compared with
changes in etco2.
Where the absence of co2 is detected instantaneously when the next
breath fails to occur.
 Capnography can be used :
To confirm correct endotracheal tube and nasal esophageal feeding tube
placement.
 Guide cardiopulmonary cerebral resuscitation (cpcr).
Assist treatment planning for patients receiving mechanical ventilatory
support.

18. Capnography Vs Pulse Oximetry

19. Capnography and CPR
The 2020 AHA guidelines for ACLS recommend using quantitative
waveform capnography in intubated patients during CPR.
 Waveform capnography allows providers to monitor:
 CPR quality,
optimize chest compressions,
detect ROSC (return of spontaneous circulation) during chest compressions.
 Non-survivors<10 mmHg
 Survivors >30 mmHg

20. Tips

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23. TIPS