Abstract
Using blood gas determinations and capnography, the relationship between arterial and end-tidal PCO2 was investigated in 20 children under halothane anaesthesia with spontaneous respiration. A median arterial to end-tidal carbon dioxide tension difference of 0.66 kPa (5 mm Hg) was found. There was a close correlation between Paco2 and the magnitude of the carbon dioxide difference. Our findings may largely be explained by an increase in Vd/Vt (presumably mainly due to a reduction of Vt) causing admixture of dead space air throughout expiration. It is concluded that though end-tidal carbon dioxide does not exactly reflect Paco2 capnography may be of value as a monitor of respiration in paediatric anaesthesia at normal or near-normal values of end-tidal carbon dioxide.
RéSUMé
A l’aide de la gazométrie et de la capnographie, on a étudié le rapport PCO2 artérielle et la PCO2 mesurée en fin d’expiration sur vingt enfants anesthésiés à l’halothane en respiration spontanée. La médiane de la différence entre la PCO2 de fin d’expiration et la Paco2 a été établie à 0.66 kPa (5 mmHg). On a trouvé une corrélation étroite entre la Paco2 et l’importance de cette différence. Nos résultats peuvent s’expliquer par une augmentation du Vd/Vt (présumément due en grande partie à une baisse du Vt) causant une contamination plus grande de l’air expiré par l’espace mort.
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References
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Valentin, N., Lomholt, B. & Thorup, M. Arterial to end-tidal carbon dioxide tension difference in children under halothane anaesthesia. Canad. Anaesth. Soc. J. 29, 12–15 (1982). https://doi.org/10.1007/BF03007941
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DOI: https://doi.org/10.1007/BF03007941