• P Deryckere, C Verborgh, and F Camu.
• Department of Anaesthesiology, Free University of Brussels, Belgium.
• Acta Anaesthesiol Belg. 2001 Jan 1; 52 (2): 191-9.

AbstractThis study evaluates spontaneous breathing and CO2-monitoring under sevoflurane anesthesia with a cuffed oropharyngeal (COPA) or laryngeal mask (LMA) as airway. Forty patients (ASA I-II) scheduled for varicose vein surgery were given 2 mg.kg-1 propofol for insertion of a COPA or a LMA. Anesthesia was maintained with sevoflurane at 2.5 vol% in 40/60% O2/N2O, while the patients breathed spontaneously. Arterial and end-tidal CO2 partial pressures (PaCO2, PE'CO2), respiratory rate (RR), tidal volume (VT) and expired minute volume (EMV) were recorded at different times before and during the procedure. The dead space (VD) was calculated from the modified Bohr equation. The PaCO2 and the PE'CO2 were generally lower in the LMA group as compared to the COPA group during most of the procedure. EMV was also higher in the LMA group as compared to the COPA group. This difference becomes statistically significant 5 min. before the end of surgery (6.22 +/- 0.34 vs. 5.23 +/- 0.39 L.min-1). RR was consistently higher in the LMA group, while VT and VD were similar. Correlation of PE'CO2 and PaCO2 was 0.87 when measured in the COPA group and 0.88 in the LMA group. The prediction of PaCO2 by PE'CO2 was more sensitive in the LMA group as compared to the COPA group. We conclude that spontaneous breathing is better with the LMA.

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