De Wolf Andre

Publications (2)0 Total impact

• Article: Can modern infrared analyzers replace gas chromatography to measure anesthetic vapor concentrations?

  Jan Hendrickx, Hendrikus Lemmens, Rik Carette, De Wolf Andre, Lawrence Saidman
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  ABSTRACT: Abstract Background Gas chromatography (GC) has often been considered the most accurate method to measure the concentration of inhaled anesthetic vapors. However, infrared (IR) gas analysis has become the clinically preferred monitoring technique because it provides continuous data, is less expensive and more practical, and is readily available. We examined the accuracy of a modern IR analyzer (M-CAiOV compact gas IR analyzer (General Electric, Helsinki, Finland) by comparing its performance with GC. Methods To examine linearity, we analyzed 3 different concentrations of 3 different agents in O₂: 0.3, 0.7, and 1.2% isoflurane; 0.5, 1, and 2% sevoflurane; and 1, 3, and 6% desflurane. To examine the effect of carrier gas composition, we prepared mixtures of 1% isoflurane, 1 or 2% sevoflurane, or 6% desflurane in 100% O₂(= O₂group); 30%O₂+ 70%N₂O (= N₂O group), 28%O₂+ 66%N₂O + 5%CO₂(= CO₂group), or air. To examine consistency between analyzers, four different M-CAiOV analyzers were tested. Results The IR analyzer response in O₂is linear over the concentration range studied: IR isoflurane % = -0.0256 + (1.006 * GC %), R = 0.998; IR sevoflurane % = -0.008 + (0.946 * GC %), R = 0.993; and IR desflurane % = 0.256 + (0.919 * GC %), R = 0.998. The deviation from GC calculated as (100*(IR-GC)/GC), in %) ranged from -11 to 11% for the medium and higher concentrations, and from -20 to +20% for the lowest concentrations. No carrier gas effect could be detected. Individual modules differed in their accuracy (p = 0.004), with differences between analyzers mounting up to 12% of the medium and highest concentrations and up to 25% of the lowest agent concentrations. Conclusion M-CAiOV compact gas IR analyzers are well compensated for carrier gas cross-sensitivity and are linear over the range of concentrations studied. IR and GC cannot be used interchangeably, because the deviations between GC and IR mount up to ± 20%, and because individual analyzers differ unpredictably in their performance.
  BMC Anesthesiology. 01/2008;
• Article: Desflurane consumption during automated closed-circuit delivery is higher than when a conventional anesthesia machine is used with a simple vaporizer-O₂-N₂O fresh gas flow sequence

  De Cooman Sofie, De Mey Nathalie, Bram Dewulf, Rik Carette, Thierry Deloof, Maurice Sosnowski, De Wolf Andre, Jan Hendrickx
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  ABSTRACT: Abstract Background The Zeus^®(Dräger, Lübeck, Germany), an automated closed-circuit anesthesia machine, uses high fresh gas flows (FGF) to wash-in the circuit and the lungs, and intermittently flushes the system to remove unwanted N₂. We hypothesized this could increase desflurane consumption to such an extent that agent consumption might become higher than with a conventional anesthesia machine (Anesthesia Delivery Unit [ADU^®], GE, Helsinki, Finland) used with a previously derived desflurane-O₂-N₂O administration schedule that allows early FGF reduction. Methods Thirty-four ASA PS I or II patients undergoing plastic, urologic, or gynecologic surgery received desflurane in O₂/N₂O. In the ADU group (n = 24), an initial 3 min high FGF of O₂and N₂O (2 and 4 L.min^-1, respectively) was used, followed by 0.3 L.min^-1O₂+ 0.4 L.min^-1N₂O. The desflurane vaporizer setting (F_D) was 6.5% for the first 15 min, and 5.5% during the next 25 min. In the Zeus group (n = 10), the Zeus^®was used in automated closed circuit anesthesia mode with a selected end-expired (F_A) desflurane target of 4.6%, and O₂/N₂O as the carrier gases with a target inspired O₂% of 30%. Desflurane F_Aand consumption during the first 40 min were compared using repeated measures one-way ANOVA. Results Age and weight did not differ between the groups (P > 0.05), but patients in the Zeus group were taller (P = 0.04). In the Zeus group, the desflurane F_Awas lower during the first 3 min (P 0.05), and slightly higher after 4 min (P < 0.05). Desflurane consumption was higher in the Zeus group at all times, a difference that persisted after correcting for the small difference in F_Abetween the two groups. Conclusion Agent consumption with an automated closed-circuit anesthesia machine is higher than with a conventional anesthesia machine when the latter is used with a specific vaporizer-FGF sequence. Agent consumption during automated delivery might be further reduced by optimizing the algorithm(s) that manages the initial FGF or by tolerating some N₂in the circuit to minimize the need for intermittent flushing.
  BMC Anesthesiology. 01/2008;