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RECLAMATION OF EXHALED VAPOUR ANESTHETIC: EVALUATION OF A NEW TECHNOLOGY

¹ University Health Network, Toronto, Canada
² Department of Anesthesia, University of Toronto, Toronto, Canada
³ Department of Anesthesia, Saint Michael's Hospital, Toronto, Canada
⁴ Blue-Zone Technologies Ltd, North York, Canada

INTRODUCTION

Some anesthetic agents are potent "greenhouse gases" and contribute to global warming. The purpose of this study was to evaluate the effectiveness of Deltazite ^TM , a hydrophobic molecular sieve adsorbent, in removing isoflurane from the gas scavenging line in a simulated clinical environment.

MATERIALS AND METHODS

In a study involving three trials, A MEDSIM^TM computerized mannequin (anesthesia simulator) was intubated (size 8 ETT) and ventilated (TV 700 ml at 10 BPM). An anesthetic machine delivered 1% isoflurane in nitrous oxide and oxygen (1:1 ratio) at a flow of 3 LPM. Airway pressures, end-tidal CO2, inspired and end-tidal isoflurane were measured. The scavenging line was connected to a canister (11.43 cm diameter; 24.13 cm height) containing 750 grams of Deltazite. Concentrations of isoflurane entering and exiting the canister were measured, as well as the pressure gradient across and the gas flow through.

The first part of each trial (phase 1) involved 6.5 hours of 1% isoflurane, followed by a second part where the simulator was replaced by a model lung. A videotaping system recorded the time to isoflurane 'breakthrough', defined as the point where the exiting isoflurane concentration exceeded 0.02%. In the final trial the Deltazite was allowed to become saturated with isoflurane, and we measured the pressure across the canister at air flow rates of 30 and 90 LPM to ensure that the canister, when saturated, does not add excessive resistance.

RESULTS

The isoflurane used averaged 92 grams while the average canister weight increase was 68 grams. The isoflurane concentration exiting the canister remained undetectable throughout phase 1 in all trials. The pressure across the canister averaged 0.13 cm H2O and did not increase throughout phase 1. In phase 2 the time to 'breakthrough' was 8.0 hours, 8.8 hours and 9.0 hours. In trial 3, with the Deltazite fully saturated, pressure across the canister was 0.64 cmH20 at 30 LPM airflow, and 2.34 cmH20 with 90 LPM airflow.

CONCLUSIONS

The Deltazite was effective at completely removing 1% isoflurane from exhaled gases for over 8 hours. This technology shows considerable promise in removing isoflurane emissions from anesthetic scavenging lines.

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