Isoflurane and Sevoflurane consumption in an anesthetic conserving device
(AnaConDa™) versus a semi-closed circle system with automatic end tidal
concentration control (Aisys Carestation™) using an artificial lung model
Iustin Georgevici, Livia Procopiuc, Dominik Drees, Vladimir Vinnikov, Jennifer Herzog-
Niescery, Heike Vogelsang, Thomas Peter Weber, Martin Belllgardt
Department for Anaesthesiology and Intensive Care, St. Josefs Hospital – Bochum
University Clinic, Bochum, Germany
Background and Goal of Study: The use of volatile anaesthetics as sedatives in the ICU
is relevant for the patient’s outcome (1). Compared to anaesthesia machines which
minimise the consumption of anaesthetic gas by recirculating it in a semi-closed circle
system, AnaConDa™ (ACD) incorporates a reflector between the breathing circuit and
the patient which captures exhaled inhalative anaesthetic and resupplies it during the next
inspiration. We aimed to compare the anaesthetic gas consumption of the ACD system
with the minimal, low and high flow consumption of a conventional semi-closed
anaesthesia machine with automatic end tidal concentration control of the volatile
anaesthetic - the Aisys CS (GE Healthcare, Madison, WI, USA).
Materials and Methods: We assembled an artificial lung model of 2x2L volume with an
additional reservoir of 3.9 L simulating the functional residual capacity. This was
connected to the ACD system, a Puritan Bennett™ 840 (Covidien, Mansfield, MA, USA)
ventilator and a Vamos monitor (Dräger, Lübeck, Germany) to measure end tidal CO2 and
expired volatile anaesthetic concentration or to an Aisys CS anaesthesia machine.
Measurements were each made continously for 30 min after achieving steady state at end
tidal concentrations of 0.5, 1.0, 1.5, 2.0 and 2.5 Vol% for Isoflurane (ISO) and Sevoflurane
(SEVO) respectively. Every measurement was repeated 3 times. The breathing parameters
were held constant (MV 5L/min, RR 10/min, TV 0.5 L). For the Aisys group measurements
for all end tidal concentrations were performed at 4 different fresh gas flows (FGF): 0.5,
1.0, 2.5 and 5 L/min respectively. The groups were compared using the Mann Whitney U
test (SPSS® v. 24.0).
Results and Discussion: For the ACD group there was no difference in consumption
when compared to the 0.5L/min fresh gas flow anaesthesia system group across the
whole range of end tidal concentrations (p>0.05). Specifically, ACD ISO consumption was
0.5-5.6 mL/h versus 0.9-5.0 mL/h for Aisys 0.5 L/min FGF (p=1). For ACD SEVO
consumption was 1.1-6.9 mL/h versus 1.0-5.3 mL/h for Aisys 0.5 L/min FGF (p=0.806).
The ACD group compared to the 1, 2.5 and 5L/min groups respectively yielded a p<0,05
each time.
Conclusions: We therefore conclude that for these fixed breathing parameters the ISO
and SEVO consumption of the ACD system are equivalent to those of a minimal flow
anaesthesia machine.
References: 1. Bellgardt M et al, 2016, Eur J Anaesthesiol 33(1):6-13

Isoflurane and Sevoflurane consumption in an anaesthetic conserving device (AnaConDa™) versus a semi-closed circle system with automatic end tidal concentration control (Aisys Carestation™) using an artificial lung model