In Vitro Performance of a Charcoal-capturing Device with Desflurane

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 .

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.

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.

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.