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Respiratory Gas Analysis (view source)
Revision as of 16:10, 25 January 2011
, 16:10, 25 January 2011no edit summary
==Introduction==
==Introduction==
Most patients undergoing a general anaesthetic are maintained on inhalation agents and therefore in a situation where they will be connected to an anaesthetic machine. This means that with the inhalation agent, oxygen or medical air will also be delivered as well as nitrous oxide in some cases. It is important, as in any anaesthetic, to monitor the respiratory function of the patient, including respiratory rate, rhythm, and effort, as well end-tidal carbon dioxide and anaesthetic agent levels if the equipment is available to do so.
Most patients undergoing a general anaesthetic are maintained on inhalation agents and therefore in a situation where they will be connected to an anaesthetic machine. This means that with the inhalation agent, oxygen or medical air will also be delivered as well as nitrous oxide in some cases. It is important, as in any anaesthetic, to monitor the respiratory function of the patient, including respiratory rate, rhythm, and effort, as well end-tidal carbon dioxide and anaesthetic agent levels if the equipment is available to do so.
==End-Tidal Carbon Dioxide==
==End-Tidal Carbon Dioxide==
End-tidal carbon dioxide is often measured via capnometry and capnorgraphy.
End-tidal carbon dioxide is often measured via capnometry and capnography.
*''Capnometry'' is the numerical display of carbon dioxide levels in the respiratory gas throughout the cycle.
*''Capnometry'' is the numerical display of carbon dioxide levels in the respiratory gas throughout the cycle.
*''Capnography'' is the graphical display of carbon dioxide levels in the respiratory gas throughout the cycle.
*''Capnography'' is the graphical display of carbon dioxide levels in the respiratory gas throughout the cycle.
===Capnograph===
===Capnograph===
# Phase 1 is the inspiratory baseline and indicates inspired carbon dioxide, therefore should be zero.
[[Image:Capnograph.JPG|left|300px]]
<center>
{| border="0.5" cellpadding="6"
|-style="background:#B0E0E6; color:black"
!'''Stage'''
!'''Represents'''
|-
|<font color=#0C1A5D> '''A''' </font>
|Exhalation of Carbon Dioxide from dead space.
End tidal carbon dioxide should be zero at this point
|- style="background:#F0F8FF; color:black"
|<font color=#0C1A5D>'''B''' </font>
|Start of phase 1.
The beginning of the respiratory upstroke.
|-
|<font color=#0C1A5D>'''C''' </font>
|End of phase 1.
The beginning of the expiratory plateau.
|- style="background:#F0F8FF; colour:black"
|<font color=#0C1A5D>'''D''' </font>
|End of the expiratory plateau.
This is the maximum end tidal carbon dioxide level.
It is the beginning of the inspiration and phase 4.
|-
|<font color=#0C1A5D>'''E''' </font>
|End of inspiration.
End tidal carbon dioxide should reach zero at this point.
|-
|}
</center>
* Phase 1 is the inspiratory baseline and indicates inspired carbon dioxide, therefore should be zero.
* Phase 2 is the expiratory upstroke and indicates the alveoli and conducting airway carbon dioxide levels.
* Phase 3 is the expiratory plateau which indicates pure alveoli carbon dioxide levels.
* Phase 4 is the inspiratory downstroke indicating the start of inspiration.
===Increases in End Tidal Carbon Dioxide===
===Increases in End Tidal Carbon Dioxide===
==Inhaled and Exhaled Anaesthetic Agents==
==Inhaled and Exhaled Anaesthetic Agents==
With some of the monitors now available it is also possible to monitor the inhaled and exhaled anaesthetic agent concentration. This allows monitoring of dosing of inhalant anaesthetics (inhaled value) and the exhaled value indicates the concentration in the circulation and brain.
With some of the monitors now available it is also possible to monitor the inhaled and exhaled anaesthetic agent concentration. This allows monitoring of dosing of inhalant anaesthetics (inhaled value) and the exhaled value indicates the concentration in the circulation and brain.
[[Category:Monitoring Anaesthesia]]