This document presents the results of a study measuring the in vitro canister life of different CO2 absorber prepacks across a range of fresh gas flows. The study found that the fractional canister usage, or amount of each canister used per hour, increased linearly as the fresh gas flow increased for each brand. The canister life was longest for the SpiraLith brand, which is lithium-based and produces no compound A or CO. Of the calcium hydroxide-based brands, Amsorb and LoFloSorb, which do not contain sodium hydroxide, were less efficient but also do not produce compound A or CO.

1. Product FICO2 = 0.1% FICO2 = 0.5%
Amsorb (Armstrong, yellow) FCU = -­­3.096*FGF + 15.48 FCU = -­­1.797*FGF+8.987
LoFloSorb (Intersurgical, light blue) FCU = -­­2.557*FGF + 12.78 FCU = -­­1.791*FGF+8.954
Medisorb (GE, red) FCU = -­­2.223*FGF + 11.11 FCU = -­­1.648*FGF+8.231
Medisorb EF (GE, pink) FCU = -­­2.472*FGF + 12.36 FCU = -­­2.009*FGF+10.05
Spherasorb (Intersurgical, dark blue)
Spiralith (Micropore, black)
FCU = -­­1.868*FGF + 9.342
FCU = -­­1.249*FGF + 6.243
FCU = -­­1.326*FGF+6.631
FCU = -­­1.186*FGF+5.931
Fractionalcanisteruse(%/h)
Fractionalcanisteruse(%/h)
In Vitro Canister Life of COs Absorber Prepacks with Different Fresh Gas Flows with
the Aisys Anesthesia Machine
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:
12
10
8
6
4
2
0
FICO2 = 0.1% FICO2 = 0.5%
20
16
12
8
4
0
0 1 2 3 4 5 FGF (L/min)
0 1 2 3 4 5 FGF (L/min)

2. 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