Prepared by Musiime Conrad Reagan. B.Sc. Biomedical Engineering Ernest Cook Ultrasound Research and Education Institute

1. Capnography
Presentation by Musiime Conrad Reagan
Bsc. Biomedical Engineering
ECUREI

2. CAPNOGRAPHY
Basically, during oxygenation, or inspiration we use oximetry is used,
cellular metabolism consumes some of the oxygen but then during
ventilation, there is need to monitor how much (by concentration)
the partial pressure of carbon dioxide. CO2
The Capnograph only captures the CO2
levels during ventilation.

3. PRINCIPLE OF OPERATION
Capnography is based on the principle that CO2
molecules absorb infrared radiation at
specific wavelengths.
When the patient exhales, a beam of infrared light is passed over the gas sample on a
sensor. The presence of CO2
in the gas leads to a reduction in the amount of light falling on
the sensor, which changes the voltage in a circuit then, the change is transduced into the
required result
However, the capnograph requires a large sample cell and high flow rate, which causes
occlusion and accuracy problems.

4. Main Parts
● Alarm limits
● Bar Graph
○ HIGHLY VISIBLE
● Respiration rate
● Airway adapter
● Power button
● EtCO2
○ AUTOUPDATED
○ EVERY BREATH

5. THE CAPNOGRAPHIC WAVEFORM
The waveform represents the amount of carbon dioxide that’s within exhaled air

6. Capnogram Phase I
Also known as Dead Space Ventilation and it occurs at the beginning of
exhalation
Characteristic: There’s no CO2
present
● It’s a result of there being no Air from trachea, posterior pharynx, mouth
and nose thus, no gaseous exchange occurs there – This creates what’s
termed as “dead space”

7. Capnogram Phase II
● Known as the ascending phase
● The carbon dioxide from the alveoli begins to reach the
upper airway and mix with the dead space air
● This causes a rapid rise in its amounts
● Thereafter, it can be detected in the exhaled air

8. Capnogram Phase III
● Alveolar plateau
● Carbon dioxide rich alveolar gas now constitutes the
majority of the exhaled air
● Characterised by the uniform concentration of Carbon
dioxide from alveoli to nose/mouth

9. Capnogram Phase III
End Tidal Volume
● Here
● Exhalation ends such that the highest concentration of
Carbon dioxide is recorded
● The “end-tidal CO2
” is the number seen on your monitor
● The Normal range for EtCO2
is 35-45mm Hg

10. Capnogram Phase IV
● Descending phase
● Inhalation begins
● Oxygen fills airway
● CO 2 level quickly drops to zero

11. Capnography Patterns
●

12. Capnography Patterns
Bronchospasm All patterns compared

13. Patient Cases
Intubated Patient Confirming ET Tube placement

14. OTHER PATIENT CASES
All cases are handled according to the documentation provided with the
Capnograph. They Include;
1. Cardiopulmonary Resuscitation _ CPR: Used to restore normal breath
rate through Chest Compressions
2. Making the decision to Cease Resuscitation
3. Optimizing ventilation
4. Non-intubated patients

15. COMMON FAULTS
1. Persistently low ETCO2
_ poor systemic perfusion
2. Unreliable Capnogram results
_ water or mucus entered into the sampling tube
3. Increased ETCO2
_Increased muscular activity (shivering) & malignant hyperthermia.

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