Adsorption of desflurane by the silica gel filters in breathing circuits: an in vitro study

Abstract

BackgroundDuring general anesthesia, a heated breathing circuit (HBC) is used to replace the heat and moisture exchange function of the upper airway. One HBC uses an air dryer filter that employs silica gel (SG) as a desiccant. SG is capable of adsorbing many organic compounds. Therefore, we undertook an in vitro study of the adsorption of desflurane by SG filters.MethodsAn HBC was connected to an anesthesia machine, and a test lung was connected to the circuit. The test lung was mechanically ventilated with 2 or 4 L/min of fresh gas flow, with and without the air dryer filter. Desflurane was administered at a 6 vol% on the vaporizer dial setting. The experiment was repeated 15 times in each group. The end-tidal concentrations were measured during the experiments. The air dryer filter weights were measured before and after the experiments, and the times required to achieve the specific end-tidal desflurane concentrations were determined.ResultsSignificant differences in the end-tidal concentrations of desflurane were observed between the control and filter groups (P < 0.001). The filter weights increased significantly after the experiments (P < 0.001). The times required to achieve the same end-tidal desflurane concentrations were different with the application of the air dryer filter (P < 0.001).ConclusionsThe adsorption of desflurane with the use of an air dryer filter was verified in this in vitro study. Careful attention is needed when using air dryer gel filters during general anesthesia.

Experimental Investigation on Water Adsorption Using Laser Photoacoustic Spectroscopy and Numerical Simulations

“…In a study by Li C. et al [ 23 ] it was proved that the area of silica holds silanol or siloxane groups that allow a distinctive interaction with water (hydrophilic), representing a particular polar group having similar properties with water. Practically, the hydrogen bonds were formed by the reaction of water and the hydroxyl group [ 23 , 24 , 25 ], and it is rational to think that water vapor adsorption, depending on the amount of the hydroxyl group on the silica surface and the adsorption ability, becomes greater in size with the hydroxyl content. By investigating a different adsorption compound with different investigation method Song et al, [ 25 ] concluded that SiO 2 is an adsorbent and a considerable number of investigations have been conducted to find specific properties of SiO 2 pearls [ 22 , 23 , 24 , 25 ], but none with the help of the photoacoustic technique.…”

Adsorption of Inhalation Anesthetics on Activated Carbon in Humid Atmosphere

“…Ang et al stated in a review article that, in particular, practical applications to separate and recycle anesthetics are still lacking. Adsorption at concentrations in the range of exhalation (0.5–6% v ) has already been investigated for various adsorbents such as activated carbons, zeolites, MOFs, and polymers. − For concentrations lower than 1000 ppm, which correspond to indoor air, pure adsorption data were presented by Ortmann et al and Bucher et al from our research group. In the case of adsorption from a humid ambient air only a few data are available.…”

Adsorption of the Inhalation Anesthetic Isoflurane from Dry and Humid Atmosphere

“…, Song et al. , and Abrahams et al. consider significantly higher concentrations (0.5–6 vol %) and use different adsorbents, such as activated carbons, zeolites, MOFs, and polymers.…”