Breathing gas from the outlet of the ventilator was scavenged (FlurAbsorb®, Sedana Medical, Uppsala, Sweden). Sample gas from the monitor was redirected into the test lung. Sample gas was drawn from the test lung side of the reflector into a gas monitor (Vamos®, Dräger Medical) connected with a personal computer for high resolution (every 10 ms) online storage of carbon dioxide and isoflurane concentrations. Carbon dioxide was administered from a bottle with pressure reducer (Air Liquide Deutschland GmbH, Düsseldorf, Germany) via an oxygen application tube (Teleflex) and a flow meter (Rotameter®, Dräger Medical) through the bronchoscopy port into the test lung. An Evita 4 ventilator (Dräger Medical, Lübeck, Germany), breathing hoses (Teleflex, Research Triangle Park, USA), the respective reflector (see below), a catheter mount with bronchoscopy port (Int’Air Medical, Bourg en Bresse, France), and a test lung (3 L manual breathing bag for Zeus® Dräger Medical) were connected in line. It was the aim of this study to quantify carbon dioxide elimination when using the AnaConDa and the M irus system in comparison to a common heat moisture exchanger and to evaluate the influence of heat and moisture as well as the presence of isoflurane in a test lung model. It has been assumed that this may be caused by an increase in dead space as well as by partial carbon dioxide reflection as described by the group of Sturesson in a test lung model as well as in patients. described an increase in the work of breathing as well as arterial carbon dioxide tension despite an increase in tidal volume when using AnaConDa during weaning off the ventilator. Currently, two devices are commercially available, AnaConDa™ (Sedana Medical, Uppsala, Sweden), and M irus™ (Pall Medical, Dreieich, Germany). Inhalation sedation has been implemented as an alternative sedation regimen in the Spanish, British, and German sedation guidelines. Under BTPS conditions and with the use of moderate inhaled agent concentrations, reflective dead space is small and similar between the two devices.Īnaesthetic reflectors are increasingly used in intensive care units to sedate critically ill patients. In addition to volumetric dead space, reflective dead space was determined as 198 ± 6/58 ± 6/35 ± 0/25 ± 0 ml under ATP/BTPS/ISO-0.4/ISO-1.2 conditions for AnaConDa, and 92 ± 6/25 ± 0/25 ± 0/25 ± 0 ml under the same conditions for M irus, respectively. Isoflurane further decreased insp-CO 2 and abolished the difference between AnaConDa and M irus. Insp-CO 2 was higher with AnaConDa compared to M irus and higher under ATP compared to BTPS. Tidal volume increase to maintain normocapnia was also determined. Inspired (insp-CO 2) and end-tidal carbon dioxide concentrations (et-CO 2) were measured under four conditions: ambient temperature pressure (ATP), body temperature pressure saturated (BTPS), BTPS with 0.4 Vol% (ISO-0.4), and 1.2 Vol% isoflurane (ISO-1.2). HME, M irus and AnaConDa were connected successively. A constant flow of carbon dioxide was insufflated into the test lung, ventilated with 500 ml, 10 breaths per minute. Therefore, we compared carbon dioxide elimination of both with a heat moisture exchanger (HME, 35 ml) in a test lung model. However, their internal volume (100 ml) and possible carbon dioxide reflection raised concerns. For this purpose, two anaesthetic reflectors, AnaConDa™ and Mirus™ are commercially available. Inhalation sedation is increasingly performed in intensive care units.
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