1.
CAPNOMETER
PRESENTED BY – DR. AMAAN QUADIR
MODERATOR- DR. SHAHNAALI

2.
DEFINITIONS
• CAPNOMETER
Capnometer is the device that performs the measurement and displays the reading.
• CAPNOMETRY
Capnometry is the measurement and numerical display of maximum inspiratory and
expiratory CO2 concentrations during a respiratory cycle.

3.
• CAPNOGRAPHY
Capnography is the graphic display of CO2 concentration versus time ( time
capnogram ) or expired volume (volume capnogram ) during a respiratory cycle.
• CAPNOGRAPH
Capnograph is the machine that generates a waveform and the capnogram is the
actual waveform.

4.
Capnography
Measurement and display of both ETCO2 value and capnogram ( CO2 waveform)
Measured by capnograph

5.
Capnometer
Measurement and display ETCO2 value (no waveform)
Measured by capnometer

6.
CARBON DIOXIDE IN CAPNOGRAPHY
Cellular Metabolism of food into energy. O2 consumption and CO2
production
Transport of O2 and CO2 between cells and pulmonary capillaries and
diffusion from /into alveoli.

7.
Ventilation between alveoli and atmosphere
• If the patient stops breathing CO2will not be able to get out. Low CO2 in
capnograph will trigger an alarm and alert the medical staffs.

8.
WORKING PRINCIPLE
• The infrared method is most widely used and most cost effective.
• This technique involves beaming of infrared light through a column of a gas
mixture, the carbon dioxide within the column subsequently absorbs part of the
infrared energy yielding a beam of less intensity at the opposite end of the
column

9.
• BEER LAMBERT LAW state that there is a linear relationship between the
concentration and absorbance of the solution , which enables the concentration
of a solution to be calculated by measuring its absorbance.

10.
• Infrared is absorbed by gases that have “two or more different atoms”.
• Oxygen molecules does not absorb infrared waves because both atoms are
same.
• Carbon dioxide , nitrous oxide, isoflurane absorb infrared waves because they
have different atoms in their structure

11.
• Infrared waves have different wavelengths
• A given gas absorbs infrared waves of different wavelengths differently.
• Carbon dioxide maximally absorbs infrared waves of wavelengths 4.25
micrometer and nitrous oxide absorbs wavelengths of 4.5 micrometer.

12.
• To be specific for a particular gas , the infrared source must emit waves having
wavelengths within narrow limits. (narrow band).
• To measure CO2 infrared source must emit a wavelength of 4.25 micrometer.

13.
CLASSIFICATION BASED ON SENSOR SITE
The basic analyser system consist consists of an infrared source, sample
chamber and detector.
Based on site of sensor it has two types:
• Diverting or Sidestream type
• Nondiverting or Mainstream type-

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DIVERTING or SIDESTREAM type – uses a pump to aspirate gas from the
sampling site to the sensor located in the main unit.

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NONDIVERTING or MAINSTREAM type- measures gas by using sensors
located in the gas stream.

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CLINICAL APPLICATIONS
• Changes in respired CO2 may reflect alterations in metabolism, circulation,
respiration, the airway, or breathing system
• Best method of verifying correct endotracheal tube (ETT) placement.
• During resuscitation, exhaled CO2 is a better guide to the presence of
circulation than the ECG, pulse, or blood pressure

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PHYSIOLOGICAL FACTOR AFFECTING ETCO2 LEVELS
INCREASE IN ETCO2
o Increased muscular activity (shivering)
o Malignant hyperthermia
o Increased cardiac output (during resuscitation)
o Bicarbonate infusion
o Tourniquet release
o Effective drug therapy for bronchospasm
o Decreased minute ventilation

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DECREASE IN ETCO2
o Decrease muscular activity (muscle relaxants)
o Hypothermia
o Decreased cardiac output (cardiac arrest)
o Pulmonary embolism
o Bronchospasm
o Increased minute ventilation

19.
CAPNOGRAMS
A NORMAL CAPNOGRAPH demonstrating the three phase of expiration
Phase 1 – dead space
Phase 2 – mixture of dead space and alveolar gas
Phase 3 – alveolar gas plateau

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PHASE 1
• Beginning of exhalation
• No CO2 present
• Air from trachea, posterior pharynx, mouth and nose or the anatomical dead
space.

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PHASE 2
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
• Depicts perfusion
Alveoli

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PHASE 3
• Plateau phase
• CO2 rich alveolar gas now constitutes the majority of the
exhaled air
• Uniform concentration of CO2 from alveoli to nose/mouth

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• End of exhalation contains the highest concentration of CO2
• The “end-tidal CO2”
• Normal EtCO2 is 35-45mmHg

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PHASE 4
• Inhalation begins
• Oxygen fills airway
• CO2 level quickly drops to zero
Alveoli

25.
Shark Fin Appearance
CAPNOGRAPH of a patient with severe Chronic Obstructive Pulmonary
Disease (COPD). No plateau is reached before the next inspiration. The
gradient between end-tidal C02 and aeterial CO2 is increased.

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CURARE CLEFT
Depression during phase 3 indicates Spontaneous respiratory effort .

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REBREATHING
Faulty expiratory valve
Inadequate inspiratory flow
Insufficient expiratory time
Malfunction of CO2 absorber system

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Hyperventilation
Increase in respiratory rate
Increase in tidal volume
Decrease in metabolic rate
Fall in body temperature

29.
Hypoventilation
Decrease in respiratory rate
Decrease in tidal volume
Increase in metabolic rate
Rapid rise in body temperature

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• Cardiac oscillations - cardiac action causes to-and-fro movement of the
interface between exhaled and fresh gas. The CO2 concentration in gas
entering the sampling line therefore alternates between high and low values.

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• Esophageal intubation – flat trace or a rapidly descending series of curves

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CPR – ACLS guidelines define high quality chest compressions as achieving
ETCO2 pressures of at least 10-20 mmHg

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CALORIMETRIC TECHNIQUE
• Specially treated litmus paper
• Colour changes indicate qualitative amount of CO2 detected
• For intubated patients only
• Disposable detector fits on ET tube hub
• Single use
• Easily impaired by moisture or secretions

34.
CAPNOMASK
• Capnomask is used for monitored anesthesia cases (MAC).
• During moderate or deep sedation the adequacy of ventilation shall be
evaluated by continual observation of qualitative clinical sign and monitoring
for the presence of exhaled CO2.

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THANK YOU