In Vitro Canister Life of COs Absorber Prepacks with Different Fresh Gas Flows with the Aisys Anesthesia Machine Spiralith (Micropore, black)
Fractional canister use (%/h)
Fractional canister use (%/h)
Presenting Author: Jan FA Hendrickx, MD, PhD, OLV Hospital, Aalst Belgium Co-­‐Authors: Lemmens H, MD, PhD, Stanford University, CA; De Hert S, MD, PhD, Gent University, Belgium; De Wolf AM, MD, Northwestern University, Chicago, IL Introduction: Low fresh gas flows (FGF) reduce inhaled anesthetic and carrier gas waste, but increase CO2 absorbent use. The performance of CO2 absorbents remains poorly studied, especially in a setting that resembles clinical practice. We measured canister life of prepacks of 6 brands over a wide FGF range. Because circuit configuration affects the rebreathing characteristics and thus performance, only those that fitted on 1 particular anesthesia machine were studied. Methods: Via a CO2 flow meter (MEDEC, Aalst, Belgium; accuracy of 3.7 mL/min), 160 mL/min CO2 flowed into the tip of a 2L breathing bag that was ventilated with an Aisys® machine (GE, Madison , WI) using controlled mechanical ventilation (tidal volume 500 mL, rate 10/min, I:E 1:1). For each brand (see Figure 1), canister life was determined for 12 canisters (all of the same lot), each of which was assigned to 1 of 12 different FGFs that ranged from 0.25 to 4 L/min O2/air (see X-­‐axis in Figure 1). For each FGF, we measured the time until the inspired CO2 (FICO2) reached either 0.1% or 0.5%. To facilitate comparison between the canisters and to easily calculate costs, this duration was converted into how much of one canister was used per hour (expressed as % of 1 canister/h); this so-­‐called “fractional canister usage” or FCU was calculated for both FICO2 thresholds. E.g., if it took 8h to FICO2 = 0.1%, FCU was 12.5 %. Because this FGF-­‐
FCU relationship turned out to be linear, performance of each brand (for each FICO2 threshold) could be described by a linear fit. Results: FICO2 = 0.1% FICO2 = 0.5% 20
12
16
10
8
12
6
8
4
4
2
0
0
0
1
2
3
4
5 FGF (L/min)
0
1
2
3
4
5 FGF (L/min)
Product
F
CO
= 0
.1%
F
CO
= 0
.5% I
2
I
2
FCU = -­‐3.096*FGF + 15.48
FCU = -­‐1.797*FGF+8.987
Amsorb (Armstrong, yellow)
LoFloSorb (Intersurgical, light blue) FCU = -­‐2.557*FGF + 12.78 FCU = -­‐1.791*FGF+8.954
FCU = -­‐2.223*FGF + 11.11
FCU = -­‐1.648*FGF+8.231
Medisorb (GE, red)
Medisorb EF (GE, pink)
FCU = -­‐2.472*FGF + 12.36
FCU = -­‐2.009*FGF+10.05 Spherasorb (Intersurgical, dark blue) FCU = -­‐1.868*FGF + 9.342
FCU = -­‐1.326*FGF+6.631
FCU = -­‐1.249*FGF + 6.243
FCU = -­‐1.186*FGF+5.931
Conclusion: The only LiOH based product, SpiraLith®, has the longest canister life and produces no compound A nor CO (1). Of the Ca(OH)2 based canisters, those without NaOH (Amsorb, LoFloSorb) are less efficient but do not produce compound A nor CO. References: (1) ASA 2010 Abstract 1693