In Vitro Performance of a Charcoal-capturing Device with Desflurane.

Background: The use of capturing devices may become required for the continued use desflurane. This study tested the percentage of desflurane captured by a charcoal filter (CONTRAfluran; Zeosys GmbH, Germany)-workstation (Aisys; GE Healthcare, USA) combination in vitro .

Methods: Desflurane in oxygen/air was administered via an Aisys workstation into a 2-l test lung that was insufflated with carbon dioxide (160 ml/min). First, to confirm that 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 and vaporizer setting combinations: 0.3 l/min and 8%, 0.5 l/min and 8%, 1 l/min and 6%, 2 l/min and 6%, 3 l/min and 6%, 4 l/min and 6%, 5 l/min and 6%, and 6 l/min and 6%. Next, to determine the effect of carbon dioxide, the capturing device weight gain was measured with the same fresh gas flow run for longer than 1 h but without desflurane. Finally, the ratio of the capturing device weight gain/vaporizer weight loss (which equals the performance, expressed as a percentage) was determined for the same 15-min runs with the 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 carbon dioxide, oxygen, and air were delivered without desflurane, the capturing device lost a relatively small amount of weight (less than 5 g), especially with fresh gas flow less than or equal to 1 l/min. Finally, performance with 0.3, 0.5 to 2, and 3 to 6 l/min fresh gas flow was 103, 100, and 95 to 93%, respectively.

Conclusions: CONTRAfluran charcoal filter in vitro performance for desflurane in oxygen/air combined with the Aisys workstation ranged from 93 to 103% with fresh gas flow of 0.3 to 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.