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Capnogram slope and ventilation dead space parameters: comparison of mainstream and sidestream techniques
A L Balogh1, F Petak2, G H Fodor3
1Department of Anaesthesiology and Intensive Therapy, University of Szeged, 6 Semmelweis u. H-6725, Szeged, Hungary Department of Medical Physics and Informatics, University of Szeged, 9 Koranyi fasor, H-6720, Szeged, Hungary.
British Journal of Anaesthesia
|June 19, 2016
Summary
Sidestream capnography reliably assesses uneven alveolar emptying and ventilation-perfusion mismatching. Mainstream capnography is required for accurate volumetric measurements like dead space and CO2 elimination.
Area of Science:
- Respiratory Physiology
- Anesthesiology
- Critical Care Medicine
Background:
- Capnography offers non-invasive bedside monitoring of lung ventilation, ventilation-perfusion (V/Q) mismatching, and metabolic status.
- Mainstream and sidestream capnography techniques exist, but their indices have not been systematically compared.
Purpose of the Study:
- To systematically compare capnographic indices obtained from simultaneous mainstream and sidestream techniques.
- To evaluate the reliability of each technique for assessing ventilation and V/Q matching.
Main Methods:
- Simultaneous mainstream and sidestream capnography were performed in anesthetized, mechanically ventilated patients undergoing heart surgery.
- Time capnography assessed phase II and III slopes (SII,T and SIII,T).
- Volumetric capnography estimated phase II and III slopes (SII,V and SIII,V), dead space (VDF, VDB, VDE), and CO2 elimination per breath.
Main Results:
- Excellent correlation and agreement were found for the phase III slope (SIII,T) between mainstream and sidestream techniques.
- Sidestream underestimated end-tidal CO2 ([Formula: see text]) but overestimated volumetric phase III slope (SIII,V).
- Agreement was excellent for intrapulmonary shunt (VDE-VDB), while [Formula: see text] showed good correlation with mild differences.
Conclusions:
- Sidestream capnography adequately assesses uneven alveolar emptying (phase III slope), end-tidal CO2, and intrapulmonary shunt.
- Mainstream capnography is necessary for reliable measurement of volumetric parameters, including phase II slope, dead space, and CO2 elimination.
Keywords:
capnographycarbon dioxideintraoperative monitoringmechanical ventilationventilation-perfusion ratioMore Related Videos
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