In vitro performance of a charcoal capturing device with desflurane.

Background: The use of capturing devices may become required for the continued use desflurane. We tested the percentage of desflurane captured by a charcoal filter (CONTRAfluran)-workstation (Aisys) combination in vitro.

Methods: Desflurane in O2/air was administered via an Aisys workstation into a 2 L test lung that was insufflated with CO2 (160 mL/min). First, to confirm all vaporized desflurane reached the capturing device, the amount of desflurane collected in a Douglas bag attached to the machine exhaust was compared to the vaporized amount during 15 min runs with the following fresh gas flow (FGF)//vaporizer setting combinations: (L/min // %): 0.3//8, 0.5//8, 1//6, 2//6, 3//6, 4//6, 5//6, and 6//6. Next, to determine the effect of CO2, the capturing device weight gain was measured with the same FGF ran over 1 hour but without desflurane. Finally, the ratio of the capturing device weight gain / vaporizer weight loss (= performance, expressed in %) was determined for the same 15 min runs with desflurane vaporizer settings described above. All experiments were arbitrarily repeated five times.

Results: The amount of vaporized desflurane did not differ from the amount collected in the Douglas bag. When CO2, O2, and air were delivered without desflurane, the capturing device lost a relatively small amount of weight (<5 g), especially with FGF ≤ 1 L/min. Finally, performance with 0.3, 0.5-2 and 3-6L/min FGF was 103, 100, and 95 - 93 %, respectively.

Conclusions: CONTRAfluran charcoal filter in vitro performance for desflurane in O2/air combined with the Aisys workstation ranged from 93-103 % with FGF of 0.3 to 3-6 L/min with vaporizer settings that reflect clinical conditions. Defining the place of charcoal filters in clinical practice requires full life cycle analysis of both the charcoal and inhaled agent.