CAPNOMETRY and CAPNOGRAPHY

1. CAPNOMETRY
DR. TANMOY ROY
CONSULTANT ANAESTHESIOLOGIST AND INTENSIVE CARE PRACTITIONER
INSTITUTE OF NEUROSCIENCE, KOLKATA

2. CAPNOMETRY ???????....................OR CAPNOGRAPHY ??????
• Capnometry is the measurement and numerical display of maximum inspiratory and
expiratory CO2 concentrations during a respiratory cycle
• Capnometer is the device that performs the measurement and displays the reading
• Capnography is the graphic display of CO2 concentration versus time (Time Capnogram)
or expired volume (Volume Capnogram) during a respiratory cycle
• Capnograph is the machine that generates a waveform and the capnogram is the actual
waveform

4. PHYSICS INVOLVED
• 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
• The resultant beam has a specific wavelength(i.e. that of carbon dioxide) and
proportional to the amount of CO2 in the mixture.
• Normal end expiratory CO2 partial pressure ranges between 35 and 45 mmHg

5. 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

6. TYPES OF CAPNOGRAPH

8. PHYSIOLOGY OF CAPNOGRAM

10. DOES ETCO2 CORRELATE WITH PACO2 ?????????
• CO2 is easily diffusible across the endothelial-alveolar membrane; thus ETCO2 -estimates
PACO2 and PaCO2
• normally differ by about 5 mm Hg
• As maldistribution between ventilation and perfusion increases, the correlation between
ETCO2and PaCO2 decreases, with ETCO2 being lower
• Increased dead space results in an increased gradient and may be associated with shock,
air embolism or thromboembolism, cardiac arrest, chronic lung disease, reactive airway
disease, or lateral decubitus positioning. Conversely, increases in cardiac output and
pulmonary blood flow will decrease the gradient

11. CAPNOGRAPHY VS. PULSE OXIMETRY
• Provides an immediate picture of patient condition. Just hold your breath to
test this theory !!!!!!

12. ABNORMAL VARIANTS