Influence of the position of charcoal air-filtration canisters on the efficacy of waste isoflurane scavenging as assessed in a randomized experiment.

Abstract

To determine whether the position or elevation of charcoal air-filtration canisters would impact efficacy of waste anesthetic gas (WAG) scavenging.Randomized experiment.2 types of bottom-vented and 1 type of top-vented charcoal air-filtration canisters (n = 8 of each canister type/evaluation session).Canisters were evaluated in a vertical or horizontal position at both low and high isoflurane gas flow rates in a modified Bain nonrebreathing circuit. Waste anesthetic gas concentrations were measured 2.54 cm from canister exhaust ports with an ambient air analyzer every 30 seconds for a maximum of 15 min/experimental condition. One type of bottom-vented canister was tested in a vertical position elevated above or suspended below the vaporizer at a high isoflurane flow rate and then a standard maintenance flow rate.Position had no significant effect on WAG emission by any canister type at low isoflurane flow rates. Horizontally positioned bottom-vented canisters at the high isoflurane flow rate emitted significantly more WAG than vertically positioned canisters. Horizontally positioned top-vented canisters at high flow rates emitted significantly more WAG than vertically positioned canisters at the final 15-minute time point only. Cannister types differed significantly in intercanister variability. Canister elevation relative to the vaporizer had no impact on WAG scavenging efficacy.Findings suggested that charcoal air-filtration canisters should be used in a vertical position when anesthetizing animals with the anesthetic delivery system used in this study.