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Volumetric capnography: reliability and reproducibility in spontaneously breathing patients
Author(s) -
Verschuren Franck,
Hein Erkki,
Clause Didier,
Zech Francis,
Reynaert Marc S.,
Liistro Giuseppe
Publication year - 2005
Publication title -
clinical physiology and functional imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.608
H-Index - 67
eISSN - 1475-097X
pISSN - 1475-0961
DOI - 10.1111/j.1475-097x.2005.00620.x
Subject(s) - medicine , capnography , mouthpiece , reproducibility , anesthesia , ventilation (architecture) , airway , tidal volume , respiratory system , mechanical engineering , statistics , mathematics , dentistry , engineering
Summary Volumetric capnography provides a breath‐by‐breath analysis of ventilation‐perfusion imbalances and deadspace volumes. The technique has been best described in intubated and ventilated patients, but promising clinical applications also concern spontaneously breathing patients. The objective of the study was to verify the reliability and reproducibility of a new capnographic program in various types of clinical conditions. In a first step, 56 patients, either healthy or with acute respiratory disorders, were connected to a sidestream gas sampler and flow sensor through a mouthpiece. An acquisition software synchronized expired CO 2 and flow data to create volumetric capnographic curves. Mixed expired CO 2 partial pressure, corresponding to the exhaled CO 2 of the effective tidal volume, was simultaneously collected in a neoprene bag for comparison. In a second step, changes in airway deadspace before and after the adjunction of known spacer volumes were compared in six healthy volunteers. The mean difference between both methods in measuring mixed expired CO 2 partial pressure was −0·9 mmHg (SE 0·2 mmHg, P <0·001). The limits of agreement extended from −4·4 to 2·5 mmHg. The interobserver correlation coefficient for reproducibility was 0·98. Airway deadspace volume, after correction for extra volumes, was not statistically different than the basic value ( P = 0·89). In conclusion, volumetric capnography can be compared with references when used in spontaneously breathing patients. Future developments and clinical applications should clarify its role as a non‐invasive method for deadspace and ventilation‐perfusion imbalances analysis.